Open AccessFeature PaperReview

Addressing Shortages with Storage: From Old Grain Pits to New Solutions for Underground Storage Systems

Antonella Pasqualone

Soil, Plant and Foods Science Department, University of Bari, Via Amendola 165 A, 70126 Bari, Italy

Agriculture 2025, 15(3), 289; https://doi.org/10.3390/agriculture15030289

Submission received: 31 December 2024 / Revised: 22 January 2025 / Accepted: 27 January 2025 / Published: 29 January 2025

(This article belongs to the Section Agricultural Product Quality and Safety)

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Abstract

In every era, climate variability and frequent food shortages have made it necessary to store harvested grains for more than one season. Underground grain storage has been used since ancient times throughout the world. Italy (Cerignola) and Malta (Valletta and Floriana) have preserved rare examples of more recent (from the 16th century onward) large concentrations of grain pits, capable of accumulating substantial reserves to cope with famine or siege. No longer in operation, they represent an important part of the cultural heritage of the agricultural economy. The purpose of this narrative review was, after a geographical framing of grain pits in the Eurasian and African macro-areas, to take the Italian and Maltese grain pits as historical case studies to draw attention to the reevaluation of underground grain storage in the context of climate change and food insecurity. Today, as in the past, grain reserves play a significant role in food security in developing countries and, due to climate change and geopolitical events that can cause disruptions in grain supplies, are also increasingly important for developed countries. A comparison of traditional and modern underground storage systems reveals the great flexibility of this technology, ranging from basic pits of different sizes to large underground granaries equipped with a support structure. The advantages of underground storage, such as environmental sustainability due to thermal insulation of the soil and airtight conditions that make high energy inputs for grain cooling and pesticide use unnecessary, are still useful today, perhaps more so than in the past. Prospects for development include technical solutions involving the application of innovative information technology-based monitoring systems and the use of modern materials to ensure the performance of waterproofing, seepage control, and static safety, all tools for further evolution of this ancient storage system.

Keywords:

granaries; hermetic storage; organic storage; matmora; tradition; Cerignola; Piano delle Fosse; Malta; cultural heritage; sustainability

1. Introduction

In every era, climate variability and frequent food shortages have made it necessary to store harvested cereals for more than one season. Storage is a response to the non-coincidence of production and consumption times and is a necessary element of any subsistence system in which food supply is irregular [1]. Underground storage has been a technique used since ancient times all over the world in dry soils with low groundwater levels [2]. Particularly common in hot, dry climates, the underground storage of grain in pits may have developed independently throughout the world where similar environmental conditions existed [3].

This storage system has been recorded in both the remote archaeological and more recent historical past [4]. Storage technologies were not just a concern of early farmers, as they have been documented in several hunter–gatherer groups when collection strategies generated surpluses that needed to be preserved for future use [5,6]. Small pits appear in pre-neolithic Middle East (Natufian, from 9000 to 7000 BC) and in neolithic Europe (from 4500 BC onward), followed, in the iron age, by larger bottle-shaped 2 m deep pits dug into suitable rock (sandstone and limestone) [7,8]. The latter were considered an indicator of greater social complexity, being related to the ability to produce surpluses [9]. Numerous pits could be grouped in the same area, a “pit site”, to increase storage capacity [10]. Pit clusters, dating from the Neolithic, Bronze Age, and Iron Age, have been found in various locations, such as Anatolia [11], Crete [12], and the northwestern Mediterranean [9,13].

Later, Marcus Terentius Varro (116–27 BC), in De Re Rustica [14], reported that grain was stored in underground caves called siri (sing. sirus) in Thrace and Cappadocia, while in Carthage and Spain, it was stored in wells called putei (sing. puteus). These underground granaries needed to be dug in dry soil, with the bottom covered with straw, sealing them after filling to prevent air and water from entering [14] (DRR 1.57.1). As the pits were well sealed, the grain’s respiration depleted oxygen and generated carbon dioxide, thus preventing the survival of pests, rodents, and even thieves. Under these conditions, the grain went into dormancy and could be stored for a period, the duration of which depended on the airtightness and impermeability of the pit [15]. Varro claimed that in the absence of air, wheat could be stored for 50 years and millet for 100 years [14] (DRR 1.57.1).

Pliny the Elder (c. AD 23–79), in his Naturalis Historia [16], provided more details and specified that grains were stored in ears, without threshing them (NH 18.73). In addition, referring to granaries in general, not only to underground ones, Varro stated that the bottom and walls should be plastered with clay mixed with straw and “amurca” [14] (DRR 1.57.1), i.e., the sediment that settles at the bottom of olive oil containers over time [17], probably to help preserve the grains by deterring insects due to its high content of phenolic compounds [18].

The use of grain pits was also common in the Middle Ages. At that time in Italy, wheat production was particularly abundant in the region of Apulia [19], where numerous grain pits were dug to store it. Sicily was also a main wheat producer, but much of the harvest was exported to Malta [20], where underground grain storage systems were similarly adopted. Derived from the Latin “fovea”, meaning “pit”, the Italian name of the pits was “fosse” (sing. “fossa”) [21], while “fosos” (sing. “foss”) was the Maltese name [22]. The pits were dug into the rock by experienced master builders who specialized in this type of construction. Their shape was ovoid, bell-shaped, or truncated cone-shaped, to minimize the surface area of the top layer of seeds, which, at the beginning of storage, was exposed to the air and had greater risk of spoilage. Grain pits could be dug in the backyards of wealthier private houses, in numbers of one or two, but mostly several dozen or even hundreds were clustered in large flat areas to concentrate the entire grain harvest for the purposes of the Annona—from the Latin, meaning “grain, means of subsistence”—which was the original system that supplied Rome’s population with grain and other foodstuffs [23]. Later, it became a centralized and politically controlled system of circulating foodstuffs, particularly grain, under papal rule [24] and in the Kingdom of Naples [25], until 1805 [24].

The areas in which grain pits were grouped were known in Apulia as “Piani delle fosse” [21], meaning “pit plans”, and in Malta as “Fuq il-Fosos”, literally “on the pits” [22]. The only pit plans surviving over time in these two countries are in the Italian city of Cerignola (Apulia region) and in the Maltese cities of Valletta and Floriana. Although no longer in operation, these pit plans represent an important part of the cultural heritage of the agricultural economy. However, grain storage in pits still plays a significant role in food security in developing countries, where it helps reduce seasonal fluctuations and cope with crop failures. At the same time, underground storage is also becoming attractive to developed countries due to climate change and geopolitical events that can cause sudden disruptions to grain supplies, making large and inexpensive storage systems necessary to increase national reserves.

It has been estimated by the Food and Agriculture Organization of the United Nations (FAO) that about one-third of food globally produced for human consumption is lost or wasted each year [26]. The post-harvest loss average rate, including storage but excluding the retail stage, is about 14% globally [27]. The highest loss, about 23%, is measured in Western Africa [28].

These figures highlight the urgent need for measures to address a problem that will increase as the world’s population grows and the frequency of extreme weather events increases. As suggested by the FAO [29], this loss can be reduced by adopting good post-harvest and storage practices, with significant improvements in food security and a positive economic impact. Such actions ensure the good use of resources and fulfil the sustainable development goals (SDGs), such as SDG 12—“responsible consumption and production”. One of the outcome targets of SDG 12 is, in fact, reducing by half the per capita global food waste at all levels, including post-harvest losses. In addition, one of its “means of implementation” targets is to support developing countries to strengthen their scientific and technological capacities, such as by providing improved storage facilities. Reducing food loss and waste also has the potential to contribute to other SDGs, including the “zero hunger” goal (SDG 2), because it helps achieve food security, improve nutrition, and promote sustainable agriculture. It also supports SDG 1, poverty eradication.

Addressing shortages with storage is an ancient and well-established approach that relies on traditional solutions rooted in the past but is now evolving by taking advantage of innovative technologies. Looking to the past to build the future is inspired by Confucius, who suggested how studying the past can preserve previously established knowledge and achievements, aiding our understanding of the present and enabling us to navigate the future more effectively. However, so far, there are no studies available in the scientific literature that delve into the historical past and, at the same time, critically analyze the technical aspects of modern grain pits to outline possible prospects for further development.

The purpose of this narrative review is to draw attention to the reevaluation of traditional grain storage in pits in the context of climate change and food insecurity. After a geographical framing of grain pits in the Eurasian and African macro-areas, Italian and Maltese grain pits are taken as historical case studies, documenting and drawing parallels between them to understand their ancient origins, operation, and decommissioning. The current situation, advantages, disadvantages, and prospects of this method of grain storage are then critically analyzed. Technical solutions involving the use of modern materials to ensure waterproofing performance, seepage control, and static safety while providing energy-sustainable resilience to environmental and climatic stresses, are examined as tools for an effective evolution of this ancient storage system.

2. Databases and Search Terms

A traditional narrative review approach was adopted. In the first step, a comprehensive literature search of the Google Scholar database was conducted to document the cultural heritage of historic grain pits by entering the following keywords: “grain pit” or “underground granary” and their plurals; “matmora”, “matmura”, “foss” or “fosos”, and “grain” or “wheat”; “fossa” and “grano”; “fovea”, “sirus”, or “puteus” and “Triticum” or “Hordeum”. No time restrictions were imposed, but only sources reporting in the Eurasian and African macro-areas were considered. In this case, Google Scholar was used because of the need to also retrieve Italian-language books and articles, as well as ancient books and Latin codices. In the second step, additional searches were conducted in the Scopus and Web of Science databases on specific topics, mostly of a technical nature, such as the basic principles of storage systems and hermetic storage, the application of information technology and artificial intelligence, the adoption of modern materials, seepage control, and the static safety of grain pits. The literature search was carried out from June 2024 to January 2025.

3. Geographical Framing: Occurrence of Grain Pits in the Eurasian and African Macro-Areas

Underground grain storage has been commonly adopted in the Mediterranean basin, the African continent, and the Near and Far East since ancient times and is still in use in some countries [30]. In addition to Italy and Malta, historic grain pits have been found in the medieval Balkans [31] and in Spain [32]. The Spanish grain pits, called sitias in Catalan, were reported in Barcelona, Tarragona, Altafulla, Urgell, and Vilafranca by the 19th century agronomist de Lasteyrie [33], who specified that in Barcelona, there were multiple grain pits (fifty-nine) grouped in the same place. He also stated that in Burjassot, near Valencia, there was another grouping of forty-nine grain pits, claiming that they would have been dug by the Moors. After being abandoned with the Catholic reconquest, these pits were repaired in 1575 for reuse and can still be seen today, although they have not been in use since the 1930s [32], nor included in the national network of granaries operating in Spain from 1951 to 1990, where farmers once pooled and stored their grain to sell to the state monopoly [34].

In Italy, although found mainly in Apulia, grain pits were also present in other regions. However, similar to Spain, they were used only in the past. In Sicily, underground granaries existed in numerous cities and rural areas, particularly in the western part of the island [35]. In the 12th–15th centuries, there were pit plans in the Sicilian towns of Sciacca, Calatafimi, Palermo, and Terranova (currently named Gela) and, more recently, in Girgenti (currently named Agrigento), Roccella, Alcamo, and Milocca [36,37]. Moreover, a document from 1182 of the Register of the Abbey of St. Mary in Monreale (Liber Privilegiorum Sanctae Montis Regalis Ecclesiae—Rollum Bullarum) mentions the existence in Monte Raitano, a hilly area close to Piana degli Albanesi, of a “hill of grain pits” [38,39]. Due to the presence of Arabs in Sicily at the time, the document refers to the hill of pits both with the Latin wording “monticulum fossarum” and with the Arabic translation “Kudyah al-Matamur” [40], “al-Matamur” being very similar to the modern Arabic word still used for grain pits, maṭmūra (pl. “maṭāmīr”, from the Arabic “ṭamara”, meaning “to hide”, indicating a natural or artificial cavity used to hide victuals or wealth) [41].

Unlike in Europe, rudimentary hand-hewn grain pits are still traditionally used in rural areas of Morocco [42,43,44], Algeria [45,46], the Horn of Africa, and India [47,48]. In Morocco, wheat that is not marketed immediately after harvest is commonly stored in the maṭmūra, near the farmer’s house, for family consumption and the next season’s seeds [43]. Also named muḍmar in Tamazight language, grain pits were the traditional on-farm storage systems in Algeria [4,49,50], as recorded in documents from the Ottoman period [50]. Algerian and Moroccan grain pits can be individual or collective; in the latter case, many pits are grouped together and supervised by a watchman [4,51,52]. Maṭāmīr were used also by the Bedouins at the border between Libya and Egypt [53], as well as in Tunisia [4] and Jordan [54].

Maṭāmīr are also traditional in Sudan [55,56,57] where, by the end of the Fur sultanate (18th century), 250 pits were recorded [58], some of which are still in use for sorghum and millet. Smaller farms have grain pits with a storage capacity of 2 to 10 tons for food security, while medium and large farms use grain pits up to more than 50 tons as collateral to obtain credit from banks for the following season. The largest pits, up to 300 tons, are dedicated to the government’s food reserve against famine, which is frequent in some Sudanese areas [55]. Traditionally, people store grains for three years [58].

Flask-shaped pits, called polota [59], are also commonly used in Ethiopia to store sorghum and maize [60,61], while in Somalia, sorghum is traditionally stored unthreshed in funnel- or flask-shaped grain pits, locally known as bakar [47,62,63]. In Yemen, grain pits (sing. madfan, pl. madāfin) have ancient origins but are still used today to store wheat, barley, sorghum, and pulses [64,65]. These pits are oblong in shape and 2–3 m deep, cut into rock or solid earth, and are usually lined with lime and ash to prevent insect infestation [66]. Underground storage pits are common also in Nigeria for cowpea, millet, and sorghum [67,68]. Examples of differently shaped grain pits from different countries are schematized in Figure 1.

Semi-nomadic Turkoman tribesmen of north-eastern Iran stored grain in underground pits up to the end of the twentieth century [69]. Storage pits are still used in India [70] for storing wheat, linseed [71], rice [72], and pulses [73]. These pits can be simply dug into the ground or lined with brick walls plastered with cement [74]. Alternatively, they can be lined with straw rope, assembled as a kind of basket to protect the grains from physical contamination by the soil [72].

Figure 1. Schematization of differently shaped grain pits from Morocco, Spain, Somalia, Yemen, and India. Adapted from [32,44,47,72].

In northwestern China, due to suitable climatic and soil conditions, grain pits have an ancient history [75] and are still used on farms for millet and wheat [76]. Bronze and early Iron Age grain pits discovered at the Shirenzigou site in Xinjiang contained barley seeds [77]. Those of the Shang dynasty were larger and deeper than the Neolithic ones, reaching 8–9 m depth [78]. The Liyang state granary located in Junxian, Henan, North China, was established under the Sui dynasty and consisted of more than 90 grain pits [75] used to store Foxtail millet and Proso millet [78]. The site was still in use during the Song dynasty, but the grain pits were replaced by above-ground granaries, probably due to the agricultural production area shifting to rice [78]. The monumental imperial granaries at Luoyang, the later Tang capital, built in early 600 CE, consisted of more than 250 large pits [79,80,81]. Supposedly part of one large state granary, they were all similarly designed and constructed, internally lined with mud mixtures, wooden planks, chaff, and woven mats [78].

In terms of stored crops, “grain pit” is the conventional name for this type of storage system, which implies the ability to store different types of grain. Historically, barley and wheat in the Mediterranean area, rice and pulses in the Asian area, and sorghum and millet in the Horn of Africa were mainly stored in this way, with more historical written documentation for wheat than for other crops. More recently, with the global spread of maize, this crop also became frequently stored, in addition to the local ones, in traditional hand-hewn structures, especially in the African area [60,82], while today’s China is rapidly increasing its storage facilities [83] and stocking maize, as well as rice, wheat, and soybeans in different types of reserves, including underground ones.

4. Case Studies from History: The Pit Plans of Cerignola and Malta

4.1. The Pit Plan of Cerignola: Reasons Behind Its Establishment

Cerignola is a town located in that area of the Apulia region (Italy) known as the “Tavoliere”, meaning “table”, to refer to the natural flatness of the land. Agriculture in the Tavoliere has been characterized since ancient times by the extensive cultivation of cereals [84], especially durum wheat, in large estates of feudal origin that amounted to hundreds and sometimes more than a thousand hectares, called “latifondi” (sing. “latifondo”) [85]. In addition to wheat, there was also minor production of barley and legumes, particularly faba beans. Fields were farmed with rotational systems, alternating with legumes, or more frequently, leaving a portion of the land fallow each year for pastoral activities. The latter were regulated by the “Dogana della mena delle pecore di Puglia” (namely, the “Customs of sheep conduction in Apulia”), established by Alfonso of Aragon in 1447. This mixed system of arable and pastoral farming led to a high production of wheat [15], which, together with the significant tributes from the transhumance of sheep, was an asset of the Kingdom of Naples [86]. The flourishing wheat trade developed in the area required a large storage capacity, which was provided by numerous grain pits concentrated in one place. The richest wheat market arose in Foggia, the main city of the Tavoliere agricultural district, but branches of it developed in the other “agro-towns” nearby (Apricena, Cerignola, Lucera, Manfredonia, San Paolo di Civitate, San Severo, Torremaggiore, and Trinitapoli) (Figure 2), which were also engaged in wheat growing and had pit plans [15,87].

Apulian pit plans were created to establish a grain reserve for the Kingdom of Naples and to facilitate the centralization of the wheat market, making it easier to estimate the amount of wheat harvested and control its use [19]. Although they were created primarily for this purpose, the pits were still also used to store barley and broad beans. Each pit plan, rationally connected to the cultivated fields, was a common space where reapers and skilled workers could easily converge for all post-harvest operations [88]. Around 1500 people were engaged in working in the pit plan of Cerignola: carters, harvesters, rope makers, brokers, owners, accountants, and “sfossatori” (unloaders), i.e., workers specialized in emptying grain pits [21]. Settled in a strategic location for trade, that is, the peri-urban area, which flanked the key route for transhumance (namely Tratturo Regio), Cerignola’s pit plan was in fact the largest after Foggia’s [87], with a remarkable total storage capacity of 350,000 quintals of grain [21].

During the Kingdom of Naples (1302–1816), wheat marketing was regulated by the Annona to meet public need and to prevent bread riots in hard times [25]. Pit plans were, therefore, of significant governmental importance, and their management was ruled and supervised to assess the quantity of each harvest with certainty and set the price accordingly [89]. Centralizing storage in public squares or state-owned sites also made it easier to calculate taxes on harvested wheat [15,89]. In fact, it would not otherwise have been possible to identify with accuracy and certainty the quantities of grain produced by all the farms scattered around the Tavoliere.

In the first half of the 17th century, Naples, the populous capital town of the Kingdom of Naples, exceeded 400,000 inhabitants, many of them destitute. To feed them, the Annona authorities had to retrieve about 2 million tomoli of wheat from the provinces, especially from Apulia [90]. So, the jurist Charles Tapia (1565–1644) advocated for the establishment of a grain depot directly in the capital town to more effectively meet its grain needs [91]. Grain pits were then established also in Naples by adapting natural cavities in an area close to the city walls, which was named the “Square of the storage of public wheat” (Piazza della Conservazione dei grani pubblici). In 1805, the Annona was abolished [24], and the grain pits of Naples were abandoned [92,93]. However, the infrastructural importance of Cerignola’s grain pits did not diminish, as they were still needed to store a very large local grain supply.

4.2. Documentary Records of Cerignola’s Grain Pits from Origins to Decommissioning

Documentary evidence from the Middle Ages shows that, initially, grain pits were located in numbers of one or two in the outbuildings of private dwellings in Cerignola and nearby towns, and only later was a large concentration of multiple grain pits established in one place, known as the pit plan. Document no. 66, dated 1225, of the Diplomatic Codex of Bari [94] (pp. 94–95) records the donation of a “house with two grain pits” in Cidiniole (“Cidiniole”, or “Cidiniola”, being the ancient name of Cerignola), and document no. 168, dated 1308 [94] (pp. 300–306), records another donation consisting of six houses in Cidiniola and other assets, including wheat and barley “contained in grain pits”. The Registers of the Angevin Chancery, particularly the 40th register of Charles of Anjou’s vicariate, opened on 1 April and closed on 4 June 1272, frequently mention the presence of household grain pits for storing wheat and barley in the nearby town of Barletta as well [95]. From the Diplomatic Code of Barletta [96] come other documents: no. 71, from 1319, concerns the donation of a house with two grain pits sited in Sancti Sabino; no. 143, from 1334, concerns the sale of a house with two grain pits in Burgo (Sancti Sabino and Burgo were two districts of Barletta); and no. 267, from 1359, reports the lease of an estate with houses and grain pits (cum domibus et foveis).

However, the existence of grain pits in the present area where the pit plan still stands is documented much later, specifically in the will of Andrea Cicchetti, dated 1573, which included “four pits for storing grain located in Piano Santo Rocco”. This will is recalled in the 1652 platea (a register of property deeds), which records the agreement made following a dispute that arose between the heirs [97]. Piano Santo Rocco is the name of the Cerignola pit plan, indicating the dedication to St. Roch. In fact, before mechanization shortened harvesting and threshing times, the liturgical feast of St. Roch (August 16) coincided with the time when wheat was loaded in the pits [21]. Another saint celebrated in August, St. Dominic, was often invoked to protect stored grain. Notably, the church bordering the pit plan is dedicated to St. Dominic.

The grain pits of Cerignola were used for centuries, even after the abolition of the Annona. Still, in 1840, a specific regulation (“Regolamento pel Piano delle Fosse di Cerignola”) was established to rule and supervise the activities of the Cerignola pit plan [85]. This regulation established two companies named after St. Roch and St. Dominic, respectively. Each was composed of 37 specialized workers (two corporals, a scribe, eight measurers, sixteen unloaders, and ten carters) who had to ensure the absence of the adulteration of the grain, supervise the good maintenance of the pits, prevent the loading of grain unfit for storage, and record the quantities of grain loaded or unloaded at the end of each working day [98].

In 1902, around 1100 pits were recorded in the Cerignola pit plan, but later, especially in the next fifty years, many were abandoned and buried to build houses as the city expanded (Figure 3). In the 1940s, the number of pits in the Cerignola pit plan decreased, but remained significant, amounting to about 750 [21]. Tommasino Conte, the Provincial Agrarian Consortium official who first carried out studies on Cerignola’s pit plan, reports that in the 1960s, the grain pits were still being used [21], and in 1981, a ministerial decree was issued to regulate the unloading of grain from the pits with specific machinery equipped with suction tubes [99].

Later, with the establishment of modern storage systems and, most importantly, with the liberalization and globalization of the grain market, local grain production lost importance compared to imported grain, and grain pits were essentially abandoned. Many industrial mills were founded in other areas and, instead of pits, above-ground vertical silos conveniently placed near each milling industry came into use. Currently, the pit plan of Cerignola, with more than 600 pits occupying 26,000 m² of area, is no longer in use and is under the protection of the Ministry of Cultural and Environmental Heritage to preserve its integrity. It represents a unicum in Italy as the last surviving example of a very large concentration of these typical grain storage facilities of the past, probably the largest worldwide (Figure 4).

4.3. Reasons Behind the Establishment of the Pit Plans in Malta

The agricultural situation in Malta was very different from that of Apulia. In fact, local grain production in Malta was low and insufficient to meet the needs of the population, so it was necessary to rely on imports [100]. Jean Quintin d’Autun, a knight of the military–religious Order of Saint John of Jerusalem, highlighted this situation in a detailed description of Malta dated 1536 [101]. Importation from Sicily was particularly facilitated by geographical proximity (Figure 5) and the exemption from taxes on grain imported from that territory, granted because Malta was part of the Kingdom of Sicily as early as the 14th century [20]. This exemption was maintained even after 1530, when Malta came under the rule of the Order of St. John [22]. The council of the city, namely the Universita, which was ruled by the Knights of St. John, oversaw the purchase of grain from Sicily for the consumption of the Maltese population, with this specific administrative function named “Massa Frumentaria” [102]. The large quantities of imported grain required equally large storage facilities. To cope with any disruption of grain imports from Sicily, not to mention the risk of siege, which was relatively easy on an island [103], the Knights of Saint John opted to build large grain pits [89]. The pits were dug into the solid limestone rock [104] and were “modeled on those of Girgenti” [105], i.e., the very large underground granaries hewn in the rock near the port of Girgenti (Agrigento), in Sicily [37,106]. The grain pits were first excavated near the palace of the Universita in Birgu, in the first half of the 16th century [22]. This reserve helped the town of Birgu resist the Great Siege of 1565 laid by the Ottomans.

In the years following the Great Siege, with the founding of a new fortress city, Valletta, facilities for the safe storage of wheat were upgraded. Grand Master Martin de Redin (1657–1660) boosted the supply of wheat from Sicily [22,107] and, later, Grand Master Ramon de Perellos (1697–1720) further promoted the construction of grain pits [107]. Then, in Valletta, seventy pits were dug near Fort St. Elmo, of which thirty-nine are still visible today (Figure 6). These pits could hold enough grain to supply the city for a year [108].

Another 15 pits, also visible today with a restored opening and curb (Figure 7), were dug in front of the Auberge de Castille, in Castille Square, under the supervision of the adjacent Annona House. The latter, erected in 1686 by Grand Master Gregorio Carafa and administered by the “Università dei grani”, managed all business related to the import of grains and other foodstuffs (Annona) and shows, above the main gate, a Latin inscription to remind that granaries were just as important as city defenses [109].

As the system of storage was reliable and efficient, the British authorities also established grain pits, especially during the governance of Richard More O’Ferrall, between 1847 and 1851 [110]. One hundred and ninety-one grain pits were dug in the town of Floriana (bordering Valletta), opposite St. Publius Church in Granary Square, which is the largest pit plan in Malta, popularly referred to as “Fuq il-Fosos” (Figure 8). Today, 76 of the original 191 grain pits are still visible, but, along with nine other pits at St. Anne’s Bastion in Floriana (Figure 9), they were all decommissioned after the 1960s [22,110]. In addition to the first grain pits located in Birgu, most of Malta’s wheat was then stored in the grain pits of Valletta and Floriana, and even today, the main Maltese pit plans can be seen in these two cities.

A timeline of the development of the grain pit plans in Malta and in Cerignola (Italy) is shown in Figure 10.

4.4. Structure of the Grain Pits of Malta and of Cerignola and Operations Related to Loading and Unloading

Maltese pits have been described as bottle-shaped [22,32] (Figure 11), beehive-shaped [108], flask-shaped [32,111], and pear-shaped [112], with a narrow mouth covered by a large stone cap, carefully sealed at the collar with mortar or cement-like pozzolan to ensure airtightness [102,111]. The curb is square or circular.

Before filling the pit, a layer of straw was placed around the walls, with a thicker layer at the bottom, to prevent the grain from absorbing moisture and fermenting. In these conditions, the storage period was about three to four years [113]. The pits can reach about 4.5 m in diameter and about 9 m in depth, with an average capacity of about 250 tons [22]. Identification of the pit is given by a number on the lid or curb (Figure 12), like those of the Burjassot pit plan in Spain [32].

Cerignola pits are truncated-cone shaped or bell-shaped [15,114] (Figure 11), internally plastered with lime and sand, usually deep 4–7 m and with a diameter, at the largest point, of 4–8 m, while the circular opening measures 1.0–1.2 m. The capacity of the largest pits reaches about 110 tons of wheat [15,114,115]. The opening is surrounded by a square curb with a side of about 1.40 m [101]. A rectangular stone 60–90 cm high is placed next to the curb, on which a monogram or sequential number is engraved to allow for the identification of the pit’s owner [114,115] (Figure 13). The Cerignola pits were covered with a mound of pressed earth to let rainwater drain away [15], and a drainage ditch was also dug around them to prevent water infiltration [114].

Before storing it in the pit, wheat had to be dried. The grain was first laid out in the sun and exposed to the wind, and then left to cool on the threshing floor. Prior to their filling, the pits were internally lined with straw, arranged in bundles supported by awls driven into the wall, to reduce moisture ingress from the walls [15].

The pits were generally filled up to 1 m from the mouth, making it necessary to ventilate them to displace carbon dioxide before unloading. The presence of carbon dioxide, however, acted as a deterrent to thieves [15]. Professional unloaders first ventilated the pit, waving canvas bags over it. After 2 or 3 h, an oil lantern was lowered into the pit: if the flame remained lit, there was sufficient oxygen, and it was possible to enter. The grain was placed in buckets that were then hoisted outside the pit with ropes [116].

5. The Current Situation: Comparison with Above-Ground Silos

Grain storage systems can be built with or without ventilation. Those with ventilation are usually above-ground silos with a vertical structure, which was made possible with the invention of the grain elevator in 1843 [37]. Grain pits and underground granaries (discussed in Section 6.1), on the other hand, are static storage systems without ventilation. The main advantages and disadvantages of above-ground silos, grain pits, and underground granaries are summarized in Table 1 and discussed below.

5.1. Above-Ground Silos: Advantages and Disadvantages

Above-ground silos are currently the most widely used grain storage system in developed countries, especially in temperate climates. In tropical and subtropical areas, warehouses are now common practice. They can be fully automated for conveying, unloading, and processing grains.

Silos are equipped with air circulation systems to maintain a grain temperature < 15 °C, at about 14 °C [117]. Temperature control slows down respiration, reducing weight loss and preventing deterioration. Ventilations are made with artificially cooled air or, at night, with naturally cool air. Harvested grain usually has a temperature of 25–35 °C, so it is necessary to ventilate it immediately after storage. Then, during its conservation, the temperature is constantly monitored at multiple measuring points using thermometric probes, and forced ventilation or refrigeration is carried out as needed [118].

The air, which is blown in from below and becomes warmer and more humid as it rises and permeates the grain mass, is then expelled through air extractors equipped with an anti-condensation device. Its expulsion prevents condensation on the metal roof of the silo, which is colder than the dew point, and the formation of a compact layer of moistened grains at the top of the stored mass, called a “cap”, which could cause mold and difficulties when unloading the silo [118]. However, refrigeration is not a disinfestation technique, as it does not kill insects but only delays their development. In fact, if it is applied late, in the presence of ongoing infestations, the insects survive in the cooled mass. Therefore, according to HACCP requirements [119], grain must be stored after pre-cleaning and, during conservation, the stored mass must be periodically checked for pest infestations. Indeed, problems of mold and subsequent grain heating are reduced, but the risk of insect and rodent attacks is not eliminated in these kinds of silos [120]. If insect proliferation occurs, fumigation with phosphines is carried out.

For organic grain lots, a modified atmosphere containing low residual oxygen is blown into the modern elevated silos, which can prevent pest infestation [121]. Sealed silos are used in this case. This treatment mimics the conditions that occur naturally in grain pits but is combined with cooling and continuous temperature monitoring to prevent fermentation.

Although they are commonly used, these storage systems have some disadvantages and are particularly hazardous if handled incorrectly. In addition to the risk of mold and insect growth and rodent attack, accidents can occur due to the lack of structural integrity of silos, causing them to collapse, and highly combustible grain dust can cause explosions. However, these risks should be put into context, as they are less probable in developed countries, where climatic conditions are generally less hot and humid, compliance with safety measures is routinely practiced, and the general infrastructure facilities are constantly maintained, effectively supporting monitoring and automation systems.

5.2. Grain Pits: Principles, Advantages, and Disadvantages

Grain pits are storage systems without ventilation because they are hermetically sealed immediately after filling, producing a controlled atmosphere through biological respiration of the grains (and any insects present), with a reduction in oxygen and an increase in carbon dioxide to levels lethal to pests [64].

The effectiveness of underground grain storage depends on several factors: silo temperature; storage time; moisture content of grain; the presence of insects in the grain batch to be stored; the characteristics of the soil in which the silos are dug; air and water infiltration from the walls (cracks, permeability) or due to leakage of the closure [122]. The results will come from the combination of these factors and will be visible only after the pit is opened, highlighting the need for constant monitoring systems for the temperature, relative humidity, and headspace composition.

The safe moisture content of cereals is <13.5% [3], higher values being associated with mold formation. It is known that in the 5–14% range, for every 1% reduction in seed moisture content, the shelf life of grain doubles [123]. For wheat or rice, a moisture content of 12.5% is the maximum limit for one year of storage at 13 °C in normal atmosphere (not airtight conditions) [117], with the best results for grain moisture ≤ 12% [124]. At moisture levels of 12–13%, grains such as sorghum undergo little change when stored under airtight conditions [64].

If there is residual air in the pit, the grain respiration process, in addition to consuming oxygen and generating carbon dioxide from the breakdown of carbohydrates, produces water in the form of moisture and energy in the form of heat. These increases in moisture and temperature due to respiration may favor the proliferation of mold and pests. An increase in temperature just above the grain pit is an indication of ongoing deterioration [3]. A grain layer several centimeters thick, called a “crust” or “cake”, consisting of germinated and/or moldy caryopses, can form near the silo walls, implying grain loss [4], which, being related to the silo area/volume ratio, decreases as the size of the silo increases [52].

When respiration has consumed all available oxygen, fermentation of the grains in contact with moist walls may occur. In Algeria, a major producer of durum wheat, where pits are still in use, the layer of fermented durum wheat found in the periphery of the pits, usually considered a loss, is valued for its organoleptic properties, particularly its strong and distinctive flavor, and is used as an ingredient in traditional dishes such as couscous. Fermented durum wheat is locally called El-Hammoum (being “Hmoum” “black” in Arabic) because of its brownish color [45,46]. It has been found that fermentation is carried out mainly by lactic acid bacteria. The isolated strains, belonging to Lactobacillus and Lactococcus genera, have antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa [46]. In addition, fermented El-Hammoum wheat shows a higher content of phenolic compounds than unfermented wheat [45].

The diffusion of external moisture due to the porosity of the rock and the surrounding soil in which the pit is dug and the possible infiltration of rainwater through cracks in the pit walls were found to be the most important deterioration factors in underground grain storage [55,63]. Water infiltration can occur through surface runoff water draining into the pit. In this case, the probability of the deterioration of stored grains can be significant, especially for storage periods longer than one year [120]. Heavy rains or floods linked to monsoon that penetrate deep into the soil can cause total pit failure [72]. To prevent grain deterioration due to groundwater seepage, it is necessary to regularly plaster the cracks in the walls [64]. Good maintenance of the pits plays a decisive role in the conservation of the grain. The pits should be opened annually to inspect the grain, taking small samples of the grain for visual and tactile examination and possibly transferring wheat to other pits lined with new straw, without exceeding three years of storage, as was suggested by Pollini already in 1856 [125].

Emptying the pit all at once is the best practice. Repeated openings for partial emptying re-expose the grain to air ingress and allow rodents and insects to enter the silo and spread [52,63]. Insect and mouse damage of up to 19% and 37%, respectively, has been observed in Somalia due to repeated openings [62].

The headspace composition that is established during airtight storage is equally fatal to humans, as it leads to asphyxiation. Varro already warned to wait a while before extracting grain from the underground silo to avoid the risk of asphyxia [14] (DRR 1.63.1). Grain pits should be vented when reopened and inspected carefully before accessing them for emptying. Traditionally, entry into storage pits was considered safe when the atmosphere supported the burning of a candle or kerosene lamp [64]. Today, multi-gas detectors are available, which can be used to check the composition of the atmosphere inside the pit.

The reasons that may have caused grain pits to be abandoned over time, especially in developed countries, include the difficulties in the process of emptying the pit and the musty smell that extracted grain sometimes gives off [126]. Operational difficulties were, indeed, the main drawback of underground grain storage, mainly because of the considerable manual labor required to fill and empty the pits [55], not to mention the risk of wall subsidence and collapse [64]. In this regard, the walls have a very gentle slope to prevent the structure from collapsing [47]. Regarding the musty smell, as early as 1783, in his book on wheat storage, Cacherano di Bricherasio [127] noted that this type of problem cannot be attributed to all pits, but only to those that had not been properly lined or had not been dug in a suitable environment, allowing air and water infiltration, as confirmed by Pollini in 1856 [125]. In 1876, Cantalupi [128] listed southern Italy, Algeria, and the Spanish regions of Extremadura and Andalusia as the most suitable areas for underground storage of wheat due to their rock composition and favorable climate. Therefore, careful site selection is essential, taking into account the type of soil and the possibility of water infiltration. Grain pits should be dug in well-drained soils, above the water table, in a flat but elevated area to ensure adequate drainage [129].

On the other hand, when properly located in a suitable environment and well managed, grain pits offer many advantages, such as security against theft and fire and relative ease of construction, especially in areas where building materials needed to build above-ground structures are scarce [61]. Pits are reusable and, with proper maintenance and a new lining, can last for many years [4].

This storage method is environmentally sustainable for two main reasons. First, it does not require pesticides, maintaining the “organic” status of the grain stock. Second, it also provides quasi-low temperature and good thermal insulation without the need for high energy input [64,130] because it takes advantage of the natural thermal characteristics and stability of the underground environment [131]. This is one of the main advantages of grain pits and passive architecture in general, making them more energy sustainable than above-ground silos [132]. For example, the climate response strategies of the ancient underground silos in Liyang, China, were identified in the thermal inertia of soil, but also in the thick overlying envelope and effective air-tightness. The overlying envelope helps silos withstand changes in the outside air temperature and protects against solar radiation. Authors proposed that the design of future grain pits could further improve shielding against solar radiation with reflective coatings and with the addition of an evaporative cooling system to further cool the temperature of the upper envelope [75].

In addition, grain pits are economically sustainable, being a low-cost storage option. For the same storage capacity, the initial capital costs of basic grain pits have recently been estimated at one-tenth those of above-ground silos [133].

5.3. Grain Pits: Traditional vs. Modern Structures

Grain pits can be relatively small and hand-dug, similar to ancient grain pits, or larger, dug with bulldozers and capable of storing hundreds of tons of grain. The former are traditionally still used by small farms in rural areas of some developing countries [134], where they help reduce seasonal fluctuations and cope with crop failures, while larger ones are currently used in some developed countries to store grains and silage near harvested fields while waiting for their price to become more profitable for the farmer [129]. Both of these types, regardless of whether they are traditional or more modern, are very basic in that they consist of simple pits in the ground that are finished, at most, by lining them with waterproof materials. For this reason, they can properly be called grain pits. More complex types of pits, equipped with a supporting structure, monitoring systems, and currently the subject of much study and innovation, are better termed “underground granaries” and are discussed in Section 6.1, along with their technical innovations.

Traditional grain pits, as those represented in Figure 1 and Figure 10, are usually plastered with fiber-reinforced clay mud and cow dung. Additionally, the base and sides are lined with a thick layer of chaff or straw. A large stone is placed on top, cemented with mud or dung to ensure an airtight seal [47]. Moreover, a rudimentary form of fumigation, lighting a fire inside the pits before use, has always been practiced to prevent pests [2].

The traditional lining of the walls and bottom of the pit with chaff, which is more hygroscopic than grain, tends to keep soil moisture away from the grain mass [55,118]. Chaff lining performs better than a mixture of mud, cow dung, and straw [3], but cannot remain in good condition for more than two seasons, which is less than farmers usually believe [57]. In any case, in areas with higher rainfall, grain pits must be emptied at the beginning of the rainy season. When pits are neither lined nor plastered with any material, grain spoilage or infestation occurs, as was frequently reported in Ethiopia [60,135]. Plastic lining of the pits, instead of straw, was proposed to ensure air and water vapor impermeability [44,61,136]. Plastic lining copes with the lack of chaff in the case of imported grain, but termites can attack plastic sheets, which cannot be ruled out in the early stages of storage, when there is still enough air in the pit for their survival [58]. The use of thick rubberized canvas [137], or thick sheets of welded polyethylene [64] is more effective. More modern grain pits can be lined with concrete [138] or metal slabs [2].

Modern grain pits meet the needs of larger farms and are similar to the intake pits used in silo complexes to receive grain from trucks or hopper wagons. However, intake pits always have a steel support structure, which is usually lacking in basic and even modern grain pits. Also, while the bottom of intake pits has a hopper with a conveyor to transport the grain to silos, grain pits have a flat base.

Compared to the traditional grain pits, the modern ones are characterized by the mechanization of first digging the pit, and then loading and unloading the grain. Their configuration is also related to the equipment available for grain handling [139,140]. Grain can be loaded into the pit by an auger or, if appropriate, can be tipped from the truck after entering the pit.

To fill the pit from above, rather than reversing the truck or bin into the pit, the safety aspect must be carefully considered. It is always necessary to avoid approaching the edge with heavy machinery to prevent the collapse of the pit side walls. A long auger must be used, the truck must be away from the pit edge by a distance at least equal to the pit depth and the ends of the pit should be as steep as possible (Figure 14A) [139]. However, if a truck, front loader, or other equipment is to work in the pit while filling or emptying, one end of the pit must have a gradual slope (no more than one in three, about 18°) to allow vehicle access (Figure 14B). In this case, the initial loads of grain are tipped by reversing into the pit, while the upper layers are then filled by an auger from above, avoiding the need to drive too close to it [140]. The longer sides of the pit, almost vertical, should have a slight outward slope to help prevent subsidence, but tipping these sides is generally unsafe. For unloading, a grain vacuum is ideal. Augers or conveyors with cross sweeps or, alternatively, loader buckets can also be used [141].

A typical pit is approximately 4 m wide and dug using a bulldozer, excavator, telescopic handler, or wheel loader, usually to a depth of approximately 4 m. The capacity, determined by the length of the pit, should be based on the amount of grain to be stored, considering that the approximate volumes per ton of grains are 1.3 m³ for wheat, 1.6 m³ for barley, and 1.9 m³ for oats [140]. The pit must be filled to a level slightly above the ground surface, forming a peak along the central axis to aid drainage [141].

The sides and base of the pit should be as smooth and solid as possible, with no protruding rocks, to avoid contaminating the grain with soil and puncturing the plastic lining placed on the internal walls and base. After filling, a top covering must be placed on the grain, consisting of a sheet of heavy plastic (such as 0.1 mm black polyethylene) which must extend 1–2 m outside the walls of the pit. All horizontal joints of the plastic sheets must overlap. Then everything must be covered with soil (a layer of 50 cm), to ensure hermetic closure [139,140]. Usually, all the soil excavated from the pit is used to cover it. Filled pits will appear as linear mounds of soil. Protecting the pit from water is the most important aspect of underground storage after choosing a dry site.

In the case of multiple pits, these should be separated by 10 m to allow for easy operational access to each one and to prevent seepage from empty pits, which could collect water, into adjacent full pits [129]. To avoid this problem, a frequent practice is to backfill the pit with soil [141].

6. Recent Developments and Future Prospects

6.1. Technical Innovation: From Grain Pits to Underground Granaries

Although grain pits are an ancient storage system, they can be attractive to modern farms, provided they are updated to meet safety and quality standards. Therefore, studies are underway to improve the efficiency and safety of underground storage. Over the past five years, Chinese scholars have been the most engaged in research on this topic and have published many papers [75,130,142,143,144,145,146,147,148,149,150,151,152,153], as the construction of underground granaries in China currently has some application value [154,155].

As the world’s largest grain consumer, whose consumption is expected to increase further from 2022 to 2031 [156], China considers it a priority to update and expand its grain storage capacity and is actively building large underground granaries (Figure 15) also in peri-urban areas [147]. Improving underground granaries as a long-term storage system has been officially recognized also by the Sudanese government as a strategy for increasing food security [3]. Establishing large storage facilities for imported grain in areas affected by persistent drought, such as Darfur, has been proposed to reduce the vulnerability of rural population [58].

Traditional grain pits typically rely only on the geologic characteristics of the rock where they are dug, and they are characterized by the absence of control systems and poor mechanization. These conditions expose the farmers to post-harvest loss [157,158,159]. Storage losses, mainly due to technically inadequate infrastructure and harsh environmental conditions, are particularly critical in developing countries, with consequent nutritional, health, economic, and social implications. Improved storage facilities will make more food available without the need to increase land and water use [76].

Studies have shown the effectiveness of modern materials in the construction of underground storage systems. After 5 years of maize storage in underground bins of metal or plastic, both having the capacity of 1.5 tons, no insect infestation was observed, and only the upper 5 cm of the grain mass showed mold [117]. Remote monitoring technologies are currently available to check the temperature of grain pits in a systematic way, detecting ongoing infestations. In addition, to ensure safe operation, gas mixture analyzers can be used to check the composition of the pit atmosphere before unloading bulk grain, and operational difficulties in filling and emptying can be overcome by unloading grain from the pits with specific machinery equipped with suction tubes [99,117].

To ensure static safety, it is necessary to check the deformation status of the underground granary support structure and its influence on adjacent buildings, based on the geological and hydrological conditions of the soil [130]. Traditional underground granary supporting structures mostly use cement materials or reinforced concrete [142], but present disadvantages, such as long periods of construction, difficulties in repairing cracks and leakages, and difficulties in demolition. Based on a steel skeleton and polymers (polyurethane foam), a new rigid–flexible composite supporting structure for underground granaries has been proposed, which is recyclable to a certain extent [147]. The use of precast steel plate–concrete composite walls has also been proposed [143]. In the latter case, the installation of an underground silo takes advantage of precast technology, but it is difficult to predict the effect of the joints connecting the precast parts on the stability of the silo under external radial pressure. A recent study showed that if the bending stiffness ratio of the joint is greater than the bending stiffness of the composite silo wall section, the walls of a precast composite silo are equivalent to the walls of a cast-in-place composite silo, allowing for the calculation of the critical pressure of the walls of the precast silo by using the same equation for the cast-in-place silo [144]. In addition, a novel vertical joint based on the trapezoidal steel plate connection was proposed. The vertical joint ensures the waterproofing performance, seepage control, and strength of precast underground silos, reducing the number of welds and lowering the construction cost [145].

Another common problem for underground granaries is the need to ensure resistance to groundwater. For this reason, grain pits are usually built under specific geological conditions with low groundwater levels. Reinforced polyethylene waterproof geomembranes are commercially available for lining the walls and bottom of the pit. Alternatively, a waterproof design has been recently tested, based on a polypropylene plastic–concrete wall [146]. Polypropylene plates, 10–20 mm thick and compliant with food contact standards, and concrete were connected by a polypropylene stud. To ensure protection from rain and vehicular traffic, robust rubber covers for grain pits, available on the market, can be used.

All underground structures, including grain pits, interact with soil and groundwater. It is particularly difficult to correctly calculate the buoyancy of underground structures in clay soils [148]. Zhang et al. [149] developed a buoyancy test device for underground cylindrical silos in sand and clay backfilling and highlighted the importance of measuring the buoyancy reduction of different soils for designing anti-floating, stable, and safe underground silos. If the degree of soil compaction around the silo increases, the floating water level increases and the vertical displacement decreases [151].

The temperature of grain in underground granaries remains quasi-low throughout the year without the need for external cooling. The temperature monitoring of an underground granary with a main structure of reinforced concrete (cylindrical shape; inner diameter = 25 m; depth = 20.06 m; side wall thickness = 0.35 m; top cover thickness, consisting of a slab of beams = 0.15 m; soil cover thickness = 1.5 m) over the course of one year, with an initial grain temperature of about 15 °C, showed that the average grain temperature was always below 17 °C. Based on these results, the authors recommended the application of underground granaries for long-term strategic grain reserves and advocated for their use to ensure food security [154,155]. The middle and lower parts of the underground granary benefit from the thermal stability of the underground environment, while the upper part, which is more exposed to outdoor conditions, can be covered with a polyurethane panel for better thermal insulation [151].

Considering that in certain situations, such as wars, it could be important to hide national grain stocks, Zhang et al. [152] studied an infrared camouflage cloak to mask underground silos, because the temperature difference between the exposed surface of an underground silo and the surrounding soil surface can be significant, which means a silo could be easily found by infrared detection [153].

As the latest development, hybrid solutions, i.e., semi-underground structures consisting of two-story squat silos, are also proposed today to achieve large grain storage capacities by combining the land-saving advantage of underground silos and the high mechanization of squat silos. The underground silo is similar in shape and size to the above-ground squat silo, that is, it is cylindrical with a conical bottom to facilitate emptying operations [154].

6.2. From Grain Pits to Modern Hermetic Storage

Ancient underground pits were an early form of hermetic storage. Hermetic storage was first studied by Navarro and Calderon in 1980 [160], and hermetic silo bag storage for grain was first applied in Argentina in the mid-1990s [161]. The United States Agency for International Development (USAID), Mercy Corps, and other non-profit organizations proposed “The Improved Seed Storage Project”, with the aim of reducing grain loss in developing countries, highlighting the effectiveness of hermetic seed storage [162]. Despite the popularity of above-ground grain storage systems, many farms, especially those in the organic sector, are increasingly considering this storage technology.

Hermetic storage is a sealed storage system that consists of low-permeability packaging containing a modified atmosphere either naturally produced by the metabolic activity of organisms (such as grains)—called “organic hermetic storage”—or artificially insufflated [163]. The hermetic storage of grain under a controlled atmosphere is as effective as refrigerated storage but at lower cost [163]. It prevents fungal growth and mycotoxin formation and allows for insect disinfestation [164]. This technical solution reduces storage-related losses and is especially suitable for smallholders and farmers because it requires a relatively modest investment and no pesticides or chemicals [158,165]. This technique has also proven to be effective in hot and humid climates, such as tropical areas [161].

To mimic the modified atmosphere (low in oxygen and rich in carbon dioxide) that is bio-generated in sealed grain pits due to grain respiration, several types of flexible hermetic plastic containers with very low oxygen permeability have been patented, which are suitable for storing various products and seeds (such as grains, legumes, nuts, coffee, and cocoa), and meet different post-harvest storage and transportation needs. They can be small, like common grain bags, such as the Purdue Improved Crop Storage (PICS) bags and GrainPro Hermetic Bag™; intermediate, such as the Super Grain Bag (SGB-Farm™), and Grain Safe Bag™; or quite large, such as the Cocoon™ (up to 300 tons), the 200-ton Silo Bag, and the giant Mega Cocoon™, with a capacity of 320–1050 tons [76,158,164]. Therefore, hermetic storage technology is very adaptable to different size requirements.

Silo bags consist of two polyethylene bags sealed and inserted into a third outer bag. The latter is made of nylon or woven polypropylene for strength. Similarly, but much smaller, PICS bags are triple-layer plastic bags designed by the College of Agriculture of Purdue University (West Lafayette, IN, USA) in collaboration with other research institutes, NGOs, and private partners. These bags are made of a low-permeability coextruded bilayer plastic film and are used as linings for conventional jute or polypropylene bags. The Cocoon™ is made of flexible UV-resistant (for outdoor use) polyvinyl chloride and is flood-proof below the zipper line. A lighter version, the Cocoon Indoor™, made of lightweight polyethylene, is designed for indoor storage. Another advantage of these storage systems is the relatively low cost per unit of grain stored, although the silo bags need to be replaced every season. The Cocoon Indoor™ is designed for one-time use but can be reused as long the material remains undamaged. Further studies should be performed to develop biodegradable hermetic bags to reduce potential waste problems. Some hermetic storage systems, such as the Grain Safe Bag™ (a 1-ton portable hermetic storage system used for bagged grains), allows for optional flushing with carbon dioxide to generate a controlled atmosphere with accelerated pest control.

Rice stored for 5 months in both GrainPro Hermetic Bags™ and PICS bags showed little changes in the moisture content (starting at around 12% and reaching a maximum of 12.5%) and remained free of pests, while rice in conventional polyethylene bags used as control reached almost a 16% moisture content, with a 5% grain loss due to insect infestation. These results were due to the perfect seal and very low permeability of the material constituting the hermetic bags, compared to the higher permeability of the conventional polyethylene bag. The water vapor transmission rates of the PICS bag, GrainPro Hermetic bag™, and polyethylene bag were 0.07, 0.09 and 0.51 g/m²/day, respectively [166]. Wheat grains experimentally infested with Tribolium castaneum were found to be free of live insects after 30 days of storage in hermetic bags, while polypropylene, jute, and cotton cloth bags were unable to protect the grains, with jute and cotton cloth performing the worst [167]. Different types of hermetic bags (PICS, Grain Pro™, SaveGrain, and Ecotact^®) were tested for 6-month storage of green gram, an important crop in India, compared to conventional polypropylene or jute bags. All the airtight systems proved to be significantly more effective in preserving the stored grains than polypropylene and jute [168]. In another experimental trial, conducted in Ghana, maize stored in airtight bags (ZeroFly^®) showed neither significant pest damage nor significant increases in the moisture content after 4 months, compared to significant changes observed with storage in polypropylene bags and cold storage, the latter being affected by unstable power supply [169]. The authors of all these studies concluded by suggesting the adoption of airtight storage by local farmers in their respective countries.

Therefore, hermetic storage has been proven to be a simple, effective technology for storing various grains, including cereals and legumes, that can be applied in developing countries. However, in some cases, it may be difficult to implement it, even in countries where they are particularly needed. A recent study showed that in Ethiopia, the vast majority (98%) of smallholder farmers still rely on conventional storage in jute or polypropylene (non-hermetic) bags [170], even though the rate of weevil damage is 30% after 7 months of storage in jute or polypropylene bags, while it is only 1.4% in PICS bags for the same storage duration [171]. Hermetic storage is more popular in the Philippines, Ghana, Rwanda, Cameroon, Mali, Niger, India, Sri Lanka, and Sudan [70,172,173], but in many other countries, there is still much work to be carried out by local policymakers to recommend modern best practices and ensure that the research-generated information reaches farmers.

The difficulties in implementing these tools can also be explained by economic aspects, although hermetic bags are relatively inexpensive. An economic analysis conducted in the sub-Saharan Africa area shows that although good-quality grain can be sold at a higher price than insect-damaged grain, in countries with low seasonal variations in grain prices, the initial investment in the hermetic bags may not be recovered by the farmers. However, their use is a good intervention to prevent food loss, so nutritional and health benefits related to reduced malnutrition, aflatoxin intake, and a reduced need for pesticides should be considered [174].

6.3. Application of Information Technologies and Artificial Intelligence

Information technology and artificial intelligence have great potential for real-time monitoring and the prediction of grain quality during storage, with the ultimate goal of achieving more effective and environmentally friendly grain storage management that requires less fumigation, which is necessary when parameters get out of control [175]. Environmental conditions (temperature, intergranular relative humidity, and carbon dioxide concentration) can be monitored by sensors that transmit the obtained data to a web server for interpretation and analysis by machine learning (ML) tools. Experimental trials have been already successfully carried out in airtight silo bags, which are similar to grain pits in terms of their principles of functioning [176,177]. Also, acoustic sensors can be used for the detection and management of insects in stored grains and underground [178]. A recent study developed a model for predicting the storage time of millet packed in double-layered polyethylene bags by using artificial neural network (ANN) and support vector regression models [179]. Results collected in real time allow for better decisions to be made when monitored variables of stored grain deviate, preventing the risk of spoilage [180].

Also, the analytical approach to monitoring has evolved. In fact, recently low-field nuclear magnetic resonance (NMR) imaging has been applied for the first time for the purpose of simultaneously checking temperature, relative humidity, and grain moisture within a grain mass. Based on this technology, a digital and cloud map monitoring system has been set up for stored grain, enabling the identification of areas of potential risk, such as fungal growth, grain sprouting, and moisture condensation [181].

7. Conclusions

Along the European coast of the Mediterranean basin, including Italy and Malta, the practical function of grain pits has been abandoned, although they remain an important part of cultural heritage associated with ancient knowledge. However, grain storage in pits plays a significant role in food security in developing countries, where it is still often practiced.

Grain reserves are an element of every country’s national security. Climate change is gradually increasing the risks of crop failure, necessitating systems that can store surpluses produced in years with sufficient rainfall. Geopolitical events may cause disruptions to grain supplies, putting a strain on food systems. Storage is a recognized risk mitigation strategy. In this context, underground granaries have recently become the subject of increasing attention in many countries as a valuable tool for strengthening national grain reserves.

The FAO’s recommendations to improve and increase the capacity of storage facilities should be taken seriously by policy makers by reevaluating this storage technology, especially since the study revealed its great flexibility, ranging from simple grain pits of different sizes to large underground granaries equipped with a support structure, making it adaptable to the resources actually available.

However, these ancient and traditional storage systems still have some drawbacks, which can be overcome by implementing modern materials, monitoring systems, and automation. Prospects for development are promising because many innovations have been proposed, and studies are still ongoing to store grains more safely, reduce losses, and maintain quality. The combination of tradition and technical innovation will make the most of the strengths of grain pits as energy-sustainable, cost-effective, soil-saving, pesticide-free systems that can withstand environmental and climatic stresses.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

No new data were created in this study. Data sharing is not applicable to this article.

Acknowledgments

The author is grateful to Pino Marzulli for invaluable help in photographing grain pits in Cerignola (Italy), Valletta (Malta) and Floriana (Malta). This research has been developed in the framework of the activities of the “Centro Interdipartimentale di Ricerca per la Cooperazione allo Sviluppo” (CPS) of the University of Bari, Italy.

Conflicts of Interest

The author declares no conflicts of interest.

References

Ingold, T. The significance of storage in hunting societies. Man 1983, 18, 553–571. [Google Scholar] [CrossRef]
Bray, F. Biology and biological technology. Part 2, Agriculture. In Science and Civilisation in China; Needham, J., Ed.; Cambridge University Press: Cambridge, UK, 1984; pp. 1–768. [Google Scholar]
Abdalla, A.T.; Stigter, C.J.; Mohamed, H.A.; Mohammed, A.T.; Gough, M.C. Effects of wall linings on moisture ingress into traditional grain storage pits. Int. J. Biometeorol. 2001, 45, 75–80. [Google Scholar] [CrossRef] [PubMed]
Bevan, A.; Cutler, B.; Hennig, C.; Yermeche, O. Cereal Silo-pits, Agro-pastoral Practices and Social Organisation in 19th Century Algeria. Hum. Ecol. 2024, 52, 497–513. [Google Scholar] [CrossRef]
Kuijt, I.; Finlayson, B. Evidence for food storage and predomestication granaries 11,000 years ago in the Jordan Valley. Proc. Natl. Acad. Sci. USA 2009, 106, 10966–10970. [Google Scholar] [CrossRef]
Binford, L.R. Constructing Frames of Reference. An Analytical Method for Archaeological Theory Building Using Ethnographic and Environmental Data Sets; University of California Press: Berkeley/Los Angeles, CA, USA, 2001; 563p. [Google Scholar]
Sigaut, F. Significance of underground storage in traditional systems of grain production. In Development in Agricultural Engineering. Controlled Atmosphere Storage of Grains; Shejbal, J., Ed.; Elsevier: Amsterdam, The Netherlands, 1980; Volume 1, pp. 3–14. [Google Scholar]
Henriksen, P.S.; Robinson, D. Early Iron Age agriculture: Archaeobotanical evidence from an underground granary at Overbygård in northern Jutland, Denmark. Veg. Hist. Archaeobot. 1996, 5, 1–11. [Google Scholar] [CrossRef]
González-Vázquez, M. Food Storage among the Iberians of the Late Iron Age Northwest Mediterranean (ca. 225-50 BC). J. Mediterr. Archaeol. 2019, 32, 149–172. [Google Scholar] [CrossRef]
Jiménez-Jáimez, V.; Suárez-Padilla, J. Understanding pit sites: Storage, surplus and social complexity in prehistoric Western Europe. J. Archaeol. Method Theory 2020, 27, 799–835. [Google Scholar] [CrossRef]
Dörfler, W.; Herking, C.; Neef, R.; Pasternak, R.; von den Driesch, A. Environment and economy in Hittite Anatolia. In Insights into Hittite History and Archaeology; Genz, H., Mielke, D.P., Eds.; Peeters: Leuven, Belgium, 2011; pp. 99–124. [Google Scholar]
Privitera, S. Long-term grain storage and political economy in Bronze Age Crete: Contextualizing Ayia Triada’s silo complexes. Am. J. Archaeol. 2014, 118, 429–449. [Google Scholar] [CrossRef]
Prats, G.; Antolín, F.; Alonso, N. From the earliest farmers to the first urban centres: A socio-economic analysis of underground storage practices in north-eastern Iberia. Antiquity 2020, 94, 653–668. [Google Scholar] [CrossRef]
Varro, M.T. De Re Rustica; Hooper, W.D.; Ash, H.B., Translators; Loeb Classical Library: London, UK, 1934; Available online: https://topostext.org/work/722 (accessed on 17 October 2024).
Iarussi, U. La scomparsa delle fosse da grano nelle città del Tavoliere di Puglia. In Capitanata, Rassegna di Vita e di Studi della Provincia di Foggia. Bollettino d’Informazione della Biblioteca Provinciale di Foggia; Biblioteca Provinciale di Foggia: Foggia, Italy, 1986; Volume 23, Part II; pp. 109–124. [Google Scholar]
Plinius, G.S. Naturalis Historia; Bostock, J.; Thomas, H., Translators; Taylor and Francis: London, UK, 1855; Available online: https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D18%3Achapter%3D73 (accessed on 16 November 2024).
Janakat, S.; Al-Nabulsi, A.; Hammad, F.; Holley, R. Effect of amurca on olive oil quality during storage. J. Food Sci. Technol. 2015, 52, 1754–1759. [Google Scholar] [CrossRef]
Levinson, H.; Levinson, A. Control of stored food pests in the ancient Orient and classical antiquity. J. Appl. Entomol. 1998, 122, 137–144. [Google Scholar] [CrossRef]
Iarussi, U. Le fosse da grano ed i mercati granari in Capitanata. Gargano Studi 1984, 7, 3–14. [Google Scholar]
Aloisio, M. A Test Case for Regional Market Integration: The Grain Trade between Malta and Sicily in the Late Middle Ages. In Money Markets and Trade in Late Medieval Europe: Essays in Honour of John H.A. Munro; Armstrong, L., Elbl, I., Elbl, M., Eds.; Brill: Boston, MA, USA, 2007; pp. 297–309. [Google Scholar]
Conte, T. Storia del Piano delle Fosse. In La Chiesa di San Domenico (1500–1900); Antonellis, L., Ed.; Edigraf: Foggia, Italy, 1997; pp. 89–102. [Google Scholar]
D’Andria, D. Il-Fosos–Underground Grain Storage in the Maltese islands. Treasures Malta 2020, 48, 47–53. [Google Scholar]
Erdkamp, P. Annona (grain). In Oxford Classical Dictionary; Whitmarsh, T., Ed.; Oxford University Press: Oxford, UK, 2016; Available online: https://oxfordre.com/classics/display/10.1093/acrefore/9780199381135.001.0001/acrefore-9780199381135-e-8000#acrefore-9780199381135-e-8000-note-49 (accessed on 30 November 2024).
Strangio, D. The Roman Annona and Its Market in the Eighteenth Century. In Italian Victualling Systems in the Early Modern Age, 16th to 18th Century; Clerici, L., Ed.; Palgrave Macmillan: Cham, Switzerland, 2021; pp. 211–249. [Google Scholar] [CrossRef]
Macry, P. Mercato e Società nel Regno di Napoli: Commercio del Grano e Politica Economica nel Regno di Napoli del ′700; Guida: Naples, Italy, 1974. [Google Scholar]
FAO. Global Food Losses and Food Waste. Extent Causes and Prevention; FAO: Rome, Italy, 2011. [Google Scholar]
FAO. The State of Food and Agriculture 2019. Moving Forward on Food Loss and Waste Reduction; FAO: Rome, Italy, 2019. [Google Scholar]
Our World in Data. Share of Food Lost in Post-Harvest Processes by Region, 2021; Data Adapted from Food and Agriculture Organization of the United Nations. Available online: https://ourworldindata.org/grapher/food-loss-postharvest-by-region (accessed on 13 January 2024).
Taruvinga, C.; Mejia, D.; Sanz Alvarez, J. Appropriate Seed and Grain Storage Systems for Small-Scale Farmers: Key Practices for DRR Implementers; FAO: Rome, Italy, 2014. [Google Scholar]
Dunkel, F.V. Underground and earth sheltered food storage: Historical, geographic, and economic considerations. Undergr. Space 1985, 9, 310–315. [Google Scholar]
Petrović, V. Food storage in Serbian medieval forts and urban settlements (XIII–XV centuries). In History or Urbanization in Europe; NNGASU: Nizhny Novgorod, Russia; Institute of History Belgrade: Belgrade, Serbia, 2023; pp. 34–46. [Google Scholar]
Valls, A.; García, F.; Ramírez, M.; Benlloch, J. Understanding subterranean grain storage heritage in the Mediterranean region: The Valencian silos (Spain). Tunn. Undergr. Space Technol. 2015, 50, 178–188. [Google Scholar] [CrossRef]
De Lasteyrie, C.P. Des Fosses Propres à la Conservation des Grains, et de la Manière de les Construire, avec Différents moyens qui Peuvent être Employés pour le Meme Objet; Imprimerie Royale: Paris, France, 1819; pp. 1–63. [Google Scholar]
Fernández-Fernández, M.V.; Marcelo, V.; Valenciano, J.B.; López-Díez, F.J. History, construction characteristics and possible reuse of Spain’s network of silos and granaries. Land Use Policy 2017, 63, 298–311. [Google Scholar] [CrossRef]
Bresc, H. Fosses à grain en Sicile [XIIe–XVe siècle]. In Les Techniques de Conservation des Grains a Long Terme: Leur Rôle dans la Dynamique des Systèmes de Cultures et des Sociétés; Gast, M., Sigaut, F., Eds.; Centre National de la Recherche Scientifique (CNRS): Paris, France, 1979; Volume 1, pp. 113–121. [Google Scholar]
Arcifa, L. Facere fossa et victualia reponere: La conservazione del grano nella Sicilia medievale. Moyen Âge 2008, 120, 39–54. [Google Scholar] [CrossRef]
Ripley, G.; Dana, C.A. The American Cyclopaedia: A Popular Dictionary of General Knowledge; D. Appleton and Co.: New York, NY, USA, 1879; Available online: https://archive.org/details/americancyclopae05ripluoft/americancyclopae05ripluoft/page/n3/mode/2up (accessed on 21 December 2024).
Johns, J. Monreale Survey: L’insediamento umano nell’alto Belice dall’età paleolitica al 1250 d.C. In Atti Giornate Internazionali di Studi Sull’area Elima; Biondi, L., Cassanelli, C., Eds.; CESDAE: Gibellina, Italy, 1992; pp. 407–420. [Google Scholar]
Mannino, G. Guida alla Preistoria del Palermitano; Istituto Siciliano Studi Politici ed Economici: Palermo, Italy, 2008; pp. 1–157. [Google Scholar]
Falletta, S. Scrittura e memoria del confine. Considerazioni in margine al Rollum Bullarum di Monreale. Mediterr. Ric. Stor. 2010, 7, 31–54. [Google Scholar]
Pellat, C. “Maṭmūra”. In Encyclopaedia of Islam Online, 2nd ed.; Bearman, P.J., Ed.; Brill: Leiden, The Netherlands, 2012. [Google Scholar] [CrossRef]
Bartali, E.H. Underground storage pits in Morocco. Tunn. Undergr. Space Technol. 1987, 2, 381–383. [Google Scholar] [CrossRef]
Bartali, E.H.; Boutfirass, M.; Yigezu, Y.A.; Niane, A.A.; Boughlala, M.; Belmakki, M.; Halila, H. Estimates of food losses and wastes at each node of the wheat value chain in Morocco: Implications on food and energy security, natural resources, and greenhouse gas emissions. Sustainability 2022, 14, 16561. [Google Scholar] [CrossRef]
Gourchala, F.; Hobamahoro, A.F.; Mihoub, F.; Henchiri, C. Effect of natural fermentation on the nutritional quality of “El hammoum” durum wheat (Triticum durum) fermented product of the Algerian country. Int. J. Biotechnol. Res. 2014, 4, 9–18. [Google Scholar]
Bartali, H.; Dunkel, F.V.; Said, A.; Sterling, R.L. Performance of plastic lining for storage of barley in traditional underground structures (Matmora) in Morocco. J. Agric. Eng. Res. 1990, 47, 297–314. [Google Scholar] [CrossRef]
Mokhtari, S.; Kheroua, O.; Saidi, D. Isolation and identification of lactic acid bacteria from Algerian durum wheat (Triticum durum) natural fermented in underground silos Matmora “El-Hammoum” and their Antimicrobial Activity Against Pathogenic Germs. J. Nutr. Health Sci. 2016, 3, 403. [Google Scholar]
Kamel, A.H. Underground storage in some Arab countries. In Controlled Atmosphere Storage of Grains; Shejbal, J., Ed.; Elsevier: Amsterdam, The Netherlands, 1980; pp. 25–38. [Google Scholar]
Peña-Chocarro, L.; Pérez Jordà, G.; Morales Mateos, J.; Zapata, L. Storage in traditional farming communities of the western Mediterranean: Ethnographic, historical and archaeological data. Environ. Archaeol. 2015, 20, 379–389. [Google Scholar] [CrossRef]
Vignet-Zunz, J. Les silos à grains enterrés dans trois populations arabes: Tell Algérien, Cyrénaïque (Libye) et Sud du Lac Tchad (Tchad)». In Les Techniques de Conservation des Grains à Long Terme: Leur Rôle dans la Dynamique des Systèmes de Cultures et des Sociétés; Gast, M., Sigaut, F., Eds.; Centre National de la Recherche Scientifique (CNRS): Paris, France, 1979; Volume 1, pp. 215–219. [Google Scholar]
Touati, I. La conservation du blé dans l’Algérie de l’époque Ottoman/The preservation of wheat in the Algeria of the Ottoman epoch. Al-Naciriya J. Sociol. Hist. Stud. 2019, 10, 884–899. Available online: https://asjp.cerist.dz/en/article/103415 (accessed on 17 October 2024).
Ferchiou, S. Conserves céréalières et rôle de la femme dans l’économie familiale en Tunisie. In Les Techniques de Conservation des Grains à Long Terme: Leur Rôle dans la Dynamique des Systemes de Cultures et des Sociétés; Gast, M., Sigaut, F., Eds.; Centre national de la Recherche Scientifique (CNRS): Paris, France, 1979; Volume 1, pp. 190–197. [Google Scholar]
Roux, P.M.J. Moisson, Battage, Vannage, Stockage des Céréales aux Périodes Protohistorique et Antique dans le Monde Egéen: Histoire des Techniques. Ph.D. Dissertation, Université Paris 1Panthéon–Sorbonne, Paris, France, 2015. [Google Scholar]
Cole, D.; Altorki, S. Agro-Pastoralism and Development in Egypt’s Northwest Coast. In Directions of Change in Rural Egypt; Hopkins, N., Westergaard, K., Eds.; American University in Cairo Press: Cairo, Egypt, 1998; pp. 1–318. [Google Scholar]
Ayoub, A. Les moyens de conservation des produits agricoles dans le nord-ouest de la Jordanie actuelle. In Les Techniques de Conservation des Grains à Long Terme: Leur Rôle dans la Dynamique des Systèmes de Cultures et des Sociétés; Gast, M., Sigaut, F., Eds.; Centre National de la Recherche Scientifique (CNRS): Paris, France, 1985; Volume 3, pp. 155–169. [Google Scholar]
Abdalla, A.T.; Stigter, C.J.; Bakhiet, N.I.; Gough, M.C.; Mohamed, H.A.; Mohammed, A.E.; Ahmed, M.A. Traditional underground grain storage in clay soils in Sudan improved by recent innovations. Tropicultura 2002, 20, 170–175. [Google Scholar]
Shazali, M.E.H. Matmura (underground pit) storage of sorghum in the Sudan. Bull. Grain Technol. 1992, 30, 207–212. [Google Scholar]
Shazali, M.E.H.; El Hadi, A.R.; Khalifa, A.M.H.; Ahmed, M.A. Environmental changes, insect control and reduction of losses in sorghum stored in matmoras (storage pits). Sudan J. Agric. Res. 1998, 1, 73–78. [Google Scholar]
Ibrahim, F.N. Combating famine by grain storage in Western Sudan. GeoJournal 1987, 14, 29–35. [Google Scholar] [CrossRef]
Sunano, Y. Traditional storage pit, polota, for storing sorghum as a long-term survival strategy in Dirashe special Worenda, Southern Ethiopia. Agroecol. Sustain. Food Syst. 2020, 44, 536–559. [Google Scholar] [CrossRef]
Muleta, O.D.; Tola, Y.B.; Hofacker, W.C. Assessment of storage losses and comparison of underground and aboveground storage for better stability and quality of maize (Zea mays L.) and sorghum (Sorghum bicolor L.) grains in selected districts of Jimma zone, Ethiopia. J. Stored Prod. Res. 2021, 93, 101847. [Google Scholar] [CrossRef]
Mulu, A.; Belayneh, Z. Comparative evaluation of underground pit storage systems for grain quality attributes in Jigjiga and Awubarre Districts of Fafen Zone, Ethiopia. Adv. Crop Sci. Technol. 2016, 4, 235. [Google Scholar] [CrossRef]
Lavigne, R.J. Stored grain insects in underground storage pits in Somalia and their control. Int. J. Trop. Insect Sci. 1991, 12, 571–578. [Google Scholar] [CrossRef]
Abdurahman, M.A. Problems of Traditional Underground Grain Storage Pits in Agropastoral Villages in Gabiley Region, Somaliland. Adv Crop Sci Tech 2023, 11, 1–5. [Google Scholar] [CrossRef]
Al-Kirshi, A.G. Storage of grain in underground pits (Madāfin). In Cahiers du CEFAS. 3. Savoirs Locaux et Agriculture Durable au Yémen (Indigenous Knowledge and Sustainable Agriculture in Yemen); Pelat, F., Al-Hakimi, A., Eds.; Centre Français de Recherche de la Péninsule Arabique, Yemeni Genetic Resources Center: Sanaa, Yemen, 2003; pp. 30–33. Available online: https://books.openedition.org/cefas/2864 (accessed on 19 October 2024).
Al-Baity, S.O. Traditional methods of grain storage in Wādī Hadramawt. In Cahiers du CEFAS. 3. Savoirs Locaux et Agriculture Durable au Yémen (Indigenous Knowledge and Sustainable Agriculture in Yemen); Pelat, F., Al-Hakimi, A., Eds.; Centre Français de Recherche de la Péninsule Arabique, Yemeni Genetic Resources Center: Sanaa, Yemen, 2003; pp. 42–47. Available online: https://books.openedition.org/cefas/2874 (accessed on 18 October 2024).
Varisco, D.M. Indigenous Plant Protection Methods in Yemen. GeoJournal 1995, 37, 27–38. [Google Scholar] [CrossRef]
Okparavero, N.F.; Grace, O.O.; Rukayat, Q.; Jimoh, O.M.; Ishola, T.D.; Okunlade, A.F.; Haruna, P.B.; Isaac, A.Y.; Akande, E.T. Effective Storage Structures for Preservation of Stored Grains in Nigeria: A Review. Ceylon J. Sci. 2024, 53, 139–147. [Google Scholar]
Mobolade, A.J.; Bunindro, N.; Sahoo, D.; Rajashekar, Y. Traditional methods of food grains preservation and storage in Nigeria and India. AOAS 2019, 64, 196–205. [Google Scholar] [CrossRef]
Lacey, J. The microbiology of cereal grains from areas of Iran with a high incidence of oesophageal cancer. J. Stored Prod. Res. 1988, 24, 39–50. [Google Scholar] [CrossRef]
Bhardwaj, S.; Sharma, R. The challenges of grain storage: A review. Int. J. Farm Sci. 2020, 10, 18–22. [Google Scholar] [CrossRef]
Gupta, A.P.; Singh, A.K. Storage Losses of Foodgrains: Comments. Econ. Polit. Wkly 1969, 4, 733–735. [Google Scholar]
Ansari, S. Understanding Storage Pits: An Ethno-Archaeological Study of Underground Grain Storage in Coastal Odisha, India. Asian Perspect. 2021, 60, 97–127. [Google Scholar] [CrossRef]
Dubey, S.K.; Saxena, H. Indigenous pulse storage methods in Bundelkhand region of Uttar Pradesh: An exploratory study. Curr Adv. Agric. Sci. 2014, 6, 161–164. [Google Scholar]
Girish, G.K. Studies on the Preservation of Foodgrains under Natural Airtight Storage. In Developments in Agricultural Engineering. Controlled Atmosphere Storage of Grains; Shejbal, J., Ed.; Elsevier: Amsterdam, The Netherlands, 1980; Volume 1, pp. 15–23. [Google Scholar]
Li, E.; Hou, R.; Yu, J.; Niu, S.; Chen, X.; Han, B.; Zhang, P. Historical vicissitudes of grain storage environment of granaries in the North China Plain. J. Asian Archit. Build. Eng. 2024, 23, 220–244. [Google Scholar] [CrossRef]
Murdock, L.L.; Baribusta, D. Hermetic storage for those who need it most—Subsistence farmers. In Proceedings of the 11th International Working Conference on Stored Product Protection, Chiang Mai, Thailand, 24–28 November 2014; Arthur, F.H., Kengkanpanich, R., Chayaprasert, W., Suthisut, D., Eds.; GrainPro: Concord, MA, USA; 2019; pp. 310–323. [Google Scholar]
Ma, Z.; Liu, S.; Ren, M.; Huan, X.; Xi, T.; Wang, J.; Ma, J. Analysis of grain storage pit of the Shirenzigou site in Balikun County, east Tianshan area, Xinjiang. Quat. Sci. 2021, 41, 214–223. [Google Scholar] [CrossRef]
Dong, S. Wooden Granaries of South China: Building Craft and Its Determining Factors. Ph.D. Dissertation, Technische Universität Wien, Wien, Austria, 2019. [Google Scholar]
Will, P.E.; Wong, R.B. Nourish the People: The State Civilian Granary System in China, 1650–1850; University of Michigan Press: Ann Arbor, MI, USA, 2020; pp. 1–634. [Google Scholar]
Xiong, V.C. The Miscellaneous Record of The Reign of the Great Enterprise And Sui Luoyang. Tang Studies 2011, 29, 6–26. [Google Scholar] [CrossRef]
Varriale, R.; Genovese, L. Underground Built Heritage (UBH) as Valuable Resource in China, Japan and Italy. Heritage 2021, 4, 3208–3237. [Google Scholar] [CrossRef]
Binga, E.; Mashavakure, N.; Makaranga, J.; Musundire, R. Pit silos require hermeticity to serve as an alternative low cost storage facility for maize grain by smallholder farmers. J. Technol. Sci. 2022, 1, 1–16. [Google Scholar] [CrossRef]
Li, F.J.; Shi, T.Y.; Cao, Y.; Wu, Y.; Tian, L. The current situation and development of grain storage technologies and facilities for Chinese farmers. J. Food Sci. Eng. 2016, 6, 260–266. [Google Scholar]
Evans, J.K. Wheat production and its social consequences in the Roman world. Class Q 1981, 31, 428–442. [Google Scholar] [CrossRef]
Labrot, G. Labrot, G. La città meridionale. In Storia del Mezzogiorno. Aspetti e Problemi del Medioevo e dell’Età Moderna; Galasso, G., Romeo, G., Eds.; Edizioni del Sole: Naples, Italy, 1992; Volume 8, pp. 215–292. [Google Scholar]
Di Simone, M.R. Istituzioni e Fonti Normative in Italia dall’Antico Regime al Fascismo; Giappichelli: Torino, Italy, 2007; pp. 82–83. [Google Scholar]
De Troia, G. Il Piano delle Fosse di Foggia e quelli della Capitanata; Schena: Fasano, Italy, 1992; pp. 204–244. [Google Scholar]
Curtis, D. Is there an ‘agro-town’ model for Southern Italy? Exploring the diverse roots and development of the agro-town structure through a comparative case study in Apulia. Contin. Change 2013, 28, 377–419. [Google Scholar] [CrossRef]
Russo, S. Grano, Pascolo e Bosco in Capitanata tra Sette e Ottocento; Edipuglia: Bari, Italy, 1990. [Google Scholar]
D’Atri, S. «Il maggior scopo è defender la testa, che è Napoli». Note sull’annona a Napoli nella seconda metà del XVII secolo. In Mercati, Regole e Crisi di Sussistenza Nelle Economie di Antico Regime; Clemente, A., Russo, S., Eds.; Rubbettino: Soveria Mannelli, Italy, 2019; pp. 107–121. [Google Scholar]
Sabatini, G. Carlo Tapia e le proposte di riforma dell’annona e delle finanze municipali nel regno di Napoli alla fine del XVI secolo. Storia Econ. 1998, 1, 121–140. [Google Scholar]
De Fusco, R. Rileggere “Napoli nobilissima”. Le Strade, le Piazze, i Quartieri; Edizioni Liguori: Napoli, Italy, 2003; pp. 1–348. [Google Scholar]
Ferraro, I. Napoli Atlante della Città Storica. Centro Antico; OIKOS Edizioni: Napoli, Italy, 2017. [Google Scholar]
Codice Diplomatico Barese. Pergamene di Barletta del R. Archivio di Napoli (1075–1309) per R. Filangieri Di Candida; Commissione Provinciale di Archeologia e Storia Patria: Bari, Italy, 1927; Volume 10. [Google Scholar]
Accademia Pontaniana. I Registri della Cancelleria Angioina Ricostruiti da Riccardo Filangieri con la Collaborazione degli Archivisti Napoletani, 1271–1272; Accademia Pontaniana: Napoli, Italy, 1957; Volume 8, pp. 1–342. Available online: http://www.accademiapontaniana.it/wp-content/uploads/2017/06/08-1271-1272-Cancelleria-Angioina.pdf (accessed on 16 October 2024).
Santeramo, S. Codice Diplomatico Barlettano; Associazione Amici dell’Arte e della Storia Barlettana: Barletta, Italy, 1931; Volume 2, p. 371. [Google Scholar]
Archivio di Stato Sezione di Foggia. Platea del Convento di S. Maria del Carmine. Atti Enti Ecclesiastici 1626–1747; Archivio di Stato Sezione di Foggia: Foggia, Italy, 1747; Volume 2, pp. 94–104.
Decurioni del Comune di Cerignola. Regolamento pel Piano delle Fosse di Cerignola. In Registro delle Deliberazioni del Decurionato, anni 1837–1840, Numero d’ordine 171; Comune di Cerignola: Cerignola, Italy, 1840; pp. 1–25. [Google Scholar]
Ministero del Lavoro e della Previdenza Sociale. Decreto 3 ottobre 1981. Modificazioni al decreto ministeriale 29 maggio 1981 concernente aggiornamento delle tariffe delle operazioni di facchinaggio del grano. GURI 1981, 295, 7027–7028. [Google Scholar]
Mallia-Milanes, V. Society and the Economy on the Hospitaller Island of Malta: An Overview. In Islands and Military Orders, c. 1291-c. 1798; Buttigieg, E., Phillips, S., Eds.; Routledge: London, UK, 2016; pp. 239–256. [Google Scholar]
Vella, H.C.R. The Earliest Description of Malta (Lyons 1536) by Jean Quintin d’Autun; DeBono Enterprises: Sliema, Malta, 1980. [Google Scholar]
De Boisgelin De Kerdu, P.M.L. Ancient and Modern Malta: Containing a Full and Accurate Account of the Present State of the Islands of Malta and Goza, the History of the Knights of St. John of Jerusalem, Also a Narrative of the Events which Attended the Capture of These Islands by the French, and Their Conquest by the English: And an Appendix, Containing Authentic State Papers and Other Documents; Richard Phillips: London, UK, 1805; Volume 1, pp. 1–328. Available online: https://books.google.it/books?id=8Mp70Rf4c1wC&printsec=frontcover&hl=it&source=gbs_ge_summary_r&cad=0#v=onepage&q=massa%20frumentaria&f=false (accessed on 27 October 2024).
Grech, I. Flow of Capital in the Mediterranean: Financial Connections between Genoa and Hospitaller Malta in the Seventeenth and Eighteenth Centuries. Int. J. Marit Hist. 2005, 17, 193–210. [Google Scholar] [CrossRef]
Gregory, D. Malta, Britain, and the European Powers, 1793–1815; Fairleigh Dickinson University Press: Madison, WI, USA, 1996; pp. 1–370. [Google Scholar]
Sultana, D.E. An English antiquary in Malta in the eighteenth century: The visit of Sir Richard Colt Hoare. JFA 1962, 2, 93–105. [Google Scholar]
Stolberg, F.L. Travels Through Germany, Switzerland, Italy, and Sicily; GG & J. Robinson: London, UK, 1797; Volume 2, pp. 1–656. Available online: https://books.google.it/books?id=wf8KAAAAYAAJ&printsec=frontcover&hl=it&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false (accessed on 17 December 2024).
Zammit, T. Malta, the Islands and Their History; Malta Herald Office: Valletta, Malta, 1926; pp. 1–472. Available online: https://dn720300.ca.archive.org/0/items/maltaislandsthei0000zamm/maltaislandsthei0000zamm.pdf (accessed on 14 November 2024).
Ray, J. Travels Through the Low Countries, Germany, Italy and France—With Curious Observations Natural, Topographical, Moral, Physiological etc. Also, a Catalogue of Plants, Found Spontaneously Growing in Those Parts, and Their Virtues; J. Walthoe: London, UK, 1738; Volume 1, pp. 1–547. Available online: https://books.google.it/books?id=f0kHAAAAQAAJ&printsec=frontcover&hl=it&source=gbs_ge_summary_r&cad=0#v=onepage&q=Elmo&f=false (accessed on 11 December 2024).
Denaro, V.F. Yet more houses in Valletta. Melita Hist. 1963, 3, 15–32. [Google Scholar]
Rizzo, V.J. Discover Floriana: Historic Walks in A Green City; Din l-Art Ħelwa & Floriana Local Council: Floriana, Malta, 2010; pp. 1–55. [Google Scholar]
Hyde, M.B.; Daubney, C.G. A study of grain storage in fossae in Malta. Trop. Sci. 1960, 2, 115–129. [Google Scholar]
Jones, H.D. Memoranda and Details of the Mode of Building Houses, & c. in the Island of Malta. In Papers on Subjects Connected with the Duties of the Corps of Royal Engineers; John Weale: London, UK, 1842; Volume 5, Available online: https://www.um.edu.mt/library/oar/bitstream/123456789/106497/3/Memoranda_and_details_of_the_mode_of_building_houses_%26c._in_the_Island_of_Malta_1842.pdf (accessed on 25 October 2024).
Bigelow, A. Travel in Malta and Sicily and Sketches of Gibraltar in 1827; Carter, Hendee and Babcock: Boston, MA, USA, 1831; pp. 1–156. [Google Scholar]
Pergola, N.; Conte, T. Il Piano delle Fosse di Cerignola tra Storia e Folclore; Centro Regionale di Servizi Educativi e Culturali—CRSEC: Cerignola, Italy, 2001.
Pergola, N.; Conte, T. Un Monumento a Rovescio. Il Piano delle Fosse di Cerignola; La Meridiana: Molfetta, Italy, 2024. [Google Scholar]
Russo, F. Fosse da grano. Medioevo 2013, 202, 94–97. [Google Scholar]
Dunkel, F.V. Applying current technologies to large-scale, underground grain storage. Tunn. Undergr. Space Technol. 1995, 10, 477–496. [Google Scholar] [CrossRef]
Rosentrater, K.A. Storage of Cereal Grains and Their Products, 5th ed.; Elsevier: Kidlington, UK, 2022. [Google Scholar]
The European Parliament and the Council of the European Union. Regulation (EC) no. 852/2004 of the European Parliament and of the Council of 29 April 2004 on the hygiene of foodstuffs. OJEU 2004, L139, 1–54. [Google Scholar]
Martorella, F. Granai e Magazzini dell’Africa Romana. Architetture e Sistemi di Conservazione delle Derrate; Quasar: Rome, Italy, 2022; pp. 1–202. [Google Scholar]
Adler, C.; Corinth, H.G.; Reichmuth, C. Modified atmospheres. In Alternatives to Pesticides in Stored-Product; Springer: New York, NY, USA, 2000; pp. 105–146. [Google Scholar]
Banks, H.J. Effects of controlled atmosphere storage on grain quality: A review. Food Technol. Aust. 1981, 33, 335–340. [Google Scholar]
Walsh, S.; Potts, M.; Remington, T.; Sperling, L.; Turner, A. Brief #1: Defining Seed Quality and Principles of Seed Storage in a Smallholder Context; Catholic Relief Services: Nairobi, Kenya, 2014; pp. 1–8. Available online: https://www.crs.org/sites/default/files/tools-research/seed-storage-briefs.pdf (accessed on 15 December 2024).
Andrews, A.; Jensen, T. Storing, Handling and Drying Grain: A Management Guide for Farms; Queensland Department of Primary Industries, Information Centre: Brisbane, Australia, 1996; pp. 1–117.
Pollini, C. Catechismo Agrario; Pellerano: Naples, Italy, 1856; pp. 1–116. [Google Scholar]
Intieri, B. Della Perfetta Conservazione del Grano; Giuseppe Raimondi: Napoli, Italy, 1754; Available online: https://books.google.it/books?hl=en&lr=&id=9E2Dc-zvfI0C&oi=fnd&pg=PA1&dq=72.%09Intieri+B.+1754.+Della+perfetta+conservazione+del+grano.+Napoli&ots=eySBJ4acuh&sig=zZCaDhBiwAj67M0MfXW-Yz_jgKQ&redir_esc=y#v=onepage&q&f=false (accessed on 10 October 2024).
Cacherano di Bricherasio, G.F.M. Della Conservazione del Grano e della Costruzione e Forma de’ Magazzeni o Granai; Luigi Chiappini e Antonio Cortesi: Macerata, Italy, 1783; pp. 1–87. Available online: https://www.byterfly.eu/islandora/object/libria:152305#page/2/mode/2up (accessed on 11 October 2024).
Cantalupi, A. Le Costruzioni Rurali. Trattato di Architettura Pratica; Galli e Omodei: Milano, Italy, 1876; pp. 345–346. [Google Scholar]
White, B.; Saunders, M.; Warrick, C. Pit stops preserve buried treasure. Res. Rep. 2024, 175, 21. [Google Scholar]
Zhao, C.; Feng, Y.; Wang, W.; Niu, Z. Mechanical properties and numerical analysis of underground continuous wall in underground grain silo foundation pit. Buildings 2023, 13, 293. [Google Scholar] [CrossRef]
Labs, K. The architectural underground. Undergr. Space 1976, 1, 1–8. [Google Scholar]
Hazbei, M.; Nematollahi, O.; Behnia, M.; Adib, Z. Reduction of energy consumption using passive architecture in hot and humid climates. Tunn. Undergr. Space Technol. 2015, 47, 16–27. [Google Scholar] [CrossRef]
White, B.; Saunders, M.; Warrick, C. Well-grounded: Storage options. Res. Rep. 2024, 175, 3–4. [Google Scholar]
Bhardwaj, S.; Sharma, R. Success of underground grain storage structures-Indian perspective. Res. J. Agric. Sci. 2024, 15, 225–226. [Google Scholar]
Shiferaw, T. Occurrence of stored grain insect pests in traditional underground pit grain storages of eastern Ethiopia. J. Biol. Agric. Healthc. 2017, 7, 1–4. [Google Scholar] [CrossRef]
Asanga, C.T.; Mills, R.B. Changes in environment, grain quality, and insect populations in pearl-millet stored in underground pits. Undergr. Space 1985, 9, 316–321. [Google Scholar]
Girma, A.; Ali, E. Comparative study of underground pit grain storage system through use of different lining materials. Agric. Sci. 2019, 1, 11–17. [Google Scholar] [CrossRef]
Olorunfemi, B.J.; Kayode, S.E. Post-harvest loss and grain storage technology-a review. TURJAF 2021, 9, 75–83. [Google Scholar] [CrossRef]
Cousins, D. Underground Storage of Grain; Government of Western Australia, Department of Primary Industries and Regional Development: Perth, WA, Australia, 2019. Available online: https://agric.wa.gov.au/n/1184 (accessed on 18 January 2025).
Hill, J.; Wedd, S. Grain storage. Underground pits. In Agfacts; D. West Government Printer: Sydney, NSW, Australia, 1986; pp. 1–3. [Google Scholar]
White, B.; Saunders, M.; Warrick, C. Pits play an important role for long game. Res. Rep. 2024, 175, 22–23. [Google Scholar]
Xiong, X.L.; Jin, L.B.; Wang, Z.Q. Earth pressure and bearing capacity analysis on the wall of reinforced concrete underground granary. J. Appl. Basic Sci. Eng. 2016, 32, 103–114. [Google Scholar]
Chuai, J.; Hou, Z.; Wang, Z.; Wang, L. Mechanical properties of the vertical joints of prefabricated underground silo steel plate concrete wall. Adv. Civ. Eng. 2020, 2020, 6643811. [Google Scholar] [CrossRef]
Zhang, H.; Wang, X.; Chen, L.; Chuai, J.; Wang, Z. Stability Analysis of Prefabricated Underground Granary Composite Silo Walls. KSCE J. Civ. Eng. 2023, 27, 4798–4811. [Google Scholar] [CrossRef]
Zhang, H.; Wang, H.; Yang, J.; Wang, F. A novel vertical waterproofing joint with trapezoidal steel plate connections for steel–concrete underground silos: Bending test and numerical simulation. Tunn. Undergr. Space Technol. 2023, 137, 105150. [Google Scholar] [CrossRef]
Zhang, H.; Pan, C.; Yang, J.; Xi, H. A hydrostatic test study on the waterproofing of an underground ecological granary using a plastic-concrete system. Structures 2022, 44, 58–71. [Google Scholar] [CrossRef]
Pan, Y.; Fang, H.; Li, B.; Wang, F. Stability analysis and full-scale test of a new recyclable supporting structure for underground ecological granaries. Eng. Struct. 2019, 192, 205–219. [Google Scholar] [CrossRef]
Guo, H.; Zhou, R.; Sun, C.; Lin, Y.; Xie, J. Buoyancy of underground structures and pore water pressure conduction law in silty clay strata. Heliyon 2024, 10, e24256. [Google Scholar] [CrossRef]
Zhang, Q.; Ouyang, L.; Wang, Z.; Liu, H.; Zhang, Y. Buoyancy reduction coefficients for underground silos in sand and clay. IGJ 2019, 49, 216–223. [Google Scholar] [CrossRef]
Xu, Z.; Yu, H. Non-contact experiment investigation of the interaction between the soil and underground granary subjected to water buoyancy. Appl. Sci. 2021, 11, 8988. [Google Scholar] [CrossRef]
Zhang, X.; Zhang, H.; Meng, Q. Research on temperature field of wheat grain piles in underground granary. Starch-Stärke 2023, 75, 2200260. [Google Scholar] [CrossRef]
Zhang, H.H.; Wang, Z.Y.; Liu, Q.; Ma, P.F. Design and simulation research on mechanical ventilation system for small underground granary. Adv. Mater. Res. 2014, 875, 2148–2151. [Google Scholar] [CrossRef]
Zhang, L.; Zhang, Q.; Ye, H. Design of infrared camouflage cloak for underground silos. Def. Technol. 2020, 16, 43–49. [Google Scholar] [CrossRef]
Jin, L.; Zhu, D.; Li, C.; Qiao, L.; Wang, X.; Wu, Q. Numerical Method-Based Grain Temperature Distribution of Semi-Underground Double-Storey Squat Silos During Static Storage. J. Food Proc. Eng. 2025, 48, e70032. [Google Scholar] [CrossRef]
Jin, L.; Li, C.; Duan, H.; Wang, Z.; Xue, Y.; Wu, Q. On-site test and numerical analysis on temperature field of an underground grain silo under static storage. J. Food Proc. Eng. 2023, 46, e14306. [Google Scholar] [CrossRef]
Zhang, X.; Bao, J.; Xu, S.; Wang, Y.; Wang, S. Prediction of China’s grain consumption from the perspective of sustainable development—Based on GM (1, 1) model. Sustainability 2022, 14, 10792. [Google Scholar] [CrossRef]
Abass, A.B.; Ndunguru, G.; Mamiro, P.; Alenkhe, B.; Mlingi, N.; Bekunda, M. Post-harvest food losses in a maize-based farming system of semi-arid savannah area of Tanzania. J. Stored Prod. Res. 2014, 57, 49–57. [Google Scholar] [CrossRef]
Kumar, D.; Kalita, P. Reducing postharvest losses during storage of grain crops to strengthen food security in developing countries. Foods 2017, 6, 8. [Google Scholar] [CrossRef]
Gustavsson, J.; Cederberg, C.; Sonesson, U.; van Otterdijk, R.; Meybeck, A. Global Food Losses and Food Waste; Food and Agriculture Organization of the United Nations: Rome, Italy, 2011. [Google Scholar]
Navarro, S.; Calderon, M. Integrated approach to the use of controlled atmospheres for insect control in grain storage. In Development in Agricultural Engineering. Controlled Atmosphere Storage of Grains; Shejbal, J., Ed.; Elsevier: Amsterdam, The Netherlands, 1980; Volume 1, pp. 73–78. [Google Scholar]
Bartosik, R. An inside look at the silo-bag system. In Proceedings of the 9th International Conference on Control Atmosphere and Fumigation in Stored Products, Antalya, Turley, 15–19 October 2012; Navarro, S., Banks, H.J., Jayas, D.S., Bell, C.H., Noyes, R.T., Ferizli, A.G., Emekci, M., Isikber, A.A., Alagusundaram, K., Eds.; ARBER Professional Congress Services: Antalya, Turkey, 2012; pp. 117–128. [Google Scholar]
Walsh, S.; Baributsa, D.; Remington, T.; Sperling, L. Brief #2: Hermetic Seed Storage Technology: Principles, Use, and Economics—A Practitioner’s Guide; Catholic Relief Services: Nairobi, Kenya, 2014; pp. 1–8. Available online: https://www.crs.org/sites/default/files/tools-research/seed-storage-briefs.pdf (accessed on 13 October 2024).
Villers, P.; Bruin, T.D.; Navarro, S. Development and applications of the hermetic storage technology. In Proceedings of the 9th International Working Conference on Stored Product Protection, Sao Paulo, Brazil, 15–18 October 2006; Lorini, I., Bacaltchuk, B., Beckel, H., Deckers, D., Sundfeld, E., dos Santos, J.P., Biagi, J.D., Celaro, J.C., Faroni, L.R.D., Bortolini, L.d.O.F., et al., Eds.; GrainPro: Concord, MA, USA, 2006; pp. 719–729. [Google Scholar]
Navarro, S. The use of modified and controlled atmospheres for the disinfestation of stored products. J. Pest. Sci. 2012, 85, 301–322. [Google Scholar] [CrossRef]
Guru, P.N.; Mridula, D.; Dukare, A.S.; Ghodki, B.M.; Paschapur, A.U.; Samal, I.; Nikhil Raj, M.; Padala, V.K.; Rajashekhar, M.; Subbanna, A.R. A comprehensive review on advances in storage pest management: Current scenario and future prospects. Front. Sustain. Food Syst. 2022, 6, 993341. [Google Scholar] [CrossRef]
Hossain, M.A.; Awal, M.A.; Ali, M.R.; Alam, M.M. Hermetic bag: An effective storage technology for rice seed/hermetic bag: A key element in enhancement of food availability. In Proceedings of the 7th International Conference on. Data Science and SDGs, Rajshahi, Bangladesh, 18–19 December 2019; Dept. of Statistics, University of Rajshahi: Rajshahi, Bangladesh, 2019; pp. 717–723. [Google Scholar]
Atta, B.; Rizwan, M.; Sabir, A.M.; Gogi, M.D.; Ali, K. Damage potential of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on wheat grains stored in hermetic and non-hermetic storage bags. Int. J. Trop. Insect. Sci. 2020, 40, 27–37. [Google Scholar] [CrossRef]
Yewle, N.; Swain, K.C.; Mann, S.; Guru, P.N. Performance of hermetic bags in green gram [Vigna radiata (L.) R. Wilczek] storage for managing pulse beetle (Callosobruchus chinensis). J. Stored Prod. Res. 2022, 95, 101896. [Google Scholar] [CrossRef]
Arthur, E.; Obeng-Akrofi, G.; Awafo, E.A.; Akowuah, J.O. Comparative assessment of three storage methods for preserving maize grain to enhance food security post COVID-19. Sci. Afr. 2023, 19, e01582. [Google Scholar] [CrossRef]
Fufa, N.; Zeleke, T.; Melese, D.; Daba, T. Assessing storage insect pests and post-harvest loss of maize in major producing areas of Ethiopia. Int. J. Agric. Sci. Food Technol. 2021, 7, 193–198. [Google Scholar]
Kuyu, C.G.; Tola, Y.B.; Mohammed, A.; Mengesh, A.; Mpagalile, J.J. Evaluation of different grain storage technologies against storage insect pests over an extended storage time. J. Stored Prod. Res. 2022, 96, 101945. [Google Scholar] [CrossRef]
Singh, V.; Verma, D.K.; Srivastav, P.P. Food Grain Storage Structures: Introduction and Applications. In Engineering Interventions in Foods and Plants; Verma, D.K., Goyal, M.R., Eds.; Apple Academic Press: Burlington, ON, Canada, 2017; pp. 247–284. [Google Scholar]
Obeng-Ofori, D.; Adarkwa, C.; Ulrichs, C. Chemical, physical and organic hermetic storage technology for stored-product protection in African countries. IOBC-WPRS Bull. 2015, 111, 3–27. [Google Scholar]
Dijkink, B.; Broeze, J.; Vollebregt, M. Hermetic bags for the storage of maize: Perspectives on economics, food security and greenhouse gas emissions in different sub-saharan African Countries. Front. Sustain. Food Syst. 2022, 6, 767089. [Google Scholar] [CrossRef]
Wu, Y.; Wu, W.; Chen, K.; Zhang, J.; Liu, Z.; Zhang, Y. Progress and Prospective in the Development of Stored Grain Ecosystems in China: From Composition, Structure, and Smart Construction to Wisdom Methodology. Agriculture 2023, 13, 1724. [Google Scholar] [CrossRef]
Coradi, P.C.; Lutz, É.; dos Santos Bilhalva, N.; Jaques, L.B.A.; Leal, M.M.; Teodoro, L.P.R. Prototype wireless sensor network and Internet of Things platform for real-time monitoring of intergranular equilibrium moisture content and predict the quality corn stored in silos bags. Expert Syst. Appl. 2022, 208, 118242. [Google Scholar] [CrossRef]
Lutz, É.; Coradi, P.C. Equilibrium moisture content and dioxide carbon monitoring in real-time to predict the quality of corn grain stored in silo bags using artificial neural networks. Food Anal. Methods 2023, 16, 1079–1098. [Google Scholar] [CrossRef]
Mankin, R.; Hagstrum, D.; Guo, M.; Eliopoulos, P.; Njoroge, A. Automated Applications of Acoustics for Stored Product Insect Detection, Monitoring, and Management. Insects 2021, 12, 259. [Google Scholar] [CrossRef] [PubMed]
Joshi, J.; Rao, P.S. Predictive modeling of allowable storage time of finger millet grains using artificial neural network and support vector regression approaches. J. Food Eng. 2024, 383, 112224. [Google Scholar] [CrossRef]
Lutz, É.; Coradi, P.C. Applications of new technologies for monitoring and predicting grains quality stored: Sensors, internet of things, and artificial intelligence. Measurement 2022, 188, 110609. [Google Scholar] [CrossRef]
Zhang, J.; Wu, W.; Liu, Z.; Wu, Y.; Han, F.; Xu, W. Development and verification of a graphical detection system for multi-field interactions in stored grain based on LF-NMR. Biosyst. Eng. 2024, 241, 15–27. [Google Scholar] [CrossRef]

Figure 2. Map of the Apulia region (Italy) showing the locations of the agro-towns of the Tavoliere (Apricena, Cerignola, Foggia, Lucera, Manfredonia, San Paolo di Civitate, San Severo, Torremaggiore, and Trinitapoli), where numerous grain pits were dug, concentrated in pit plans.

Figure 3. Aerial view of the pit plan of Cerignola (Italy). The red border shows an almost intact main part of the plan, surrounded, especially on the left, by fragmented portions of the original plan, the remainder of which was buried to build houses and roads.

Figure 4. Partial view of the pit plan of Cerignola (Italy). Originally 1100, about 600 remain today.

Figure 5. Map of Malta showing the proximity with Sicily and the locations of Valletta, Floriana, and Birgu, the cities facing the Grand Harbor, where grain pits were dug.

Figure 6. Grain pits near Fort St. Elmo, in Valletta (Malta). Originally numbered 70, of which 39 remain today.

Figure 7. Grain pits, with a restored opening and curb, located in Castille Square, Valletta (Malta). The Auberge de Castille is on the right, while the Annona House is in the central background. A total of fifteen pits are still visible today.

Figure 8. Grain pits in Granary Square, opposite St. Publius Church, Floriana (Malta). This is the largest pit plan in Malta, popularly referred to as “Fuq il-Fosos”. The pits, precisely aligned, originally numbered 191, of which 76 remain today.

Figure 9. Grain pits near the St. Anne’s Bastion in Floriana (Malta). A total of nine pits can still be seen today.

Figure 10. Timeline of the development of grain pit plans in Malta and in Cerignola (Italy).

Figure 11. Schematization of bottle-shaped grain pit in Floriana (Malta) and of truncated-cone shaped and bell-shaped grain pits in Cerignola (Italy). Adapted from [20,101,102].

Figure 12. Sequential number on the curb of a grain pit (no. “60” in this example) in Granary Square, Floriana (Malta).

Figure 13. Sequential number (no. “726”) and monogram (“MG”, standing for “Magazzini Generali”) engraved on the identification stone of a grain pit in the Cerignola’s pit plan (Italy).

Figure 14. (A) Schematization (longitudinal and cross-section) of a grain pit with steep edges, to be loaded from above. (B) Schematization (longitudinal and cross-section) of a grain pit with a gradual slope to allow vehicle access. The plastic lining is shown in blue. Adapted from [129,139,140].

Figure 15. Underground silo. Adapted from [154,155].

Table 1. Advantages and disadvantages of above-ground silos, grain pits, and underground granaries.

Characteristic	Above-Ground Silos	Grain Pits	Underground Granaries
Cost-effectiveness		X
Fire resistance		X	X
Thief resistance		X	X
Reduction of building material requirement		X
Collapse risk		X
Automation of loading and unloading	X		X
Ease of monitoring	X		X
Ease of inspection	X
Organic handling	X *	X	X
Low energy consumption for thermal control		X

* Potentially.

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Pasqualone, A. Addressing Shortages with Storage: From Old Grain Pits to New Solutions for Underground Storage Systems. Agriculture 2025, 15, 289. https://doi.org/10.3390/agriculture15030289

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Pasqualone A. Addressing Shortages with Storage: From Old Grain Pits to New Solutions for Underground Storage Systems. Agriculture. 2025; 15(3):289. https://doi.org/10.3390/agriculture15030289

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Pasqualone, Antonella. 2025. "Addressing Shortages with Storage: From Old Grain Pits to New Solutions for Underground Storage Systems" Agriculture 15, no. 3: 289. https://doi.org/10.3390/agriculture15030289

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Pasqualone, A. (2025). Addressing Shortages with Storage: From Old Grain Pits to New Solutions for Underground Storage Systems. Agriculture, 15(3), 289. https://doi.org/10.3390/agriculture15030289

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