Indian Journal of Agricultural Sciences 86 (10): 1343–9, October 2016/Article https://doi.org/10.56093/ijas.v86i10.62136 Response of varieties of elephant foot yam (Amorphophallus paeoniifolius) to organic management G SUJA1, A N JYOTHI2 and G BYJU3 ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, Kerala 695 017 Received: 22 November 2015; Accepted: 4 August 2016 ABSTRACT Consumer awareness regarding the impacts of high-input chemical intensive conventional agriculture on the soil, environment and human health has spurred the growth of organic agriculture systems. Organic agriculture ensures sustainable production, safe food and environmental conservation. It is estimated that more than 95% of organic production is based on crop varieties that were bred for the conventional high-input sector. Such varieties lack important traits required under organic and low-input production conditions. There is dearth of information on the response of varieties to organic management. Field experiments were conducted for two years during 2010 and 2011 at the Central Tuber Crops Research Institute, Thiruvananthapuram, to compare the growth, yield and quality performance of five elephant foot yam [Amorphallus paeoniifolius (Dennst.) Nicolson] varieties (Peerumade local, Gajendra, Sree Padma, Vegetable and Fruit Promotion Council Keralam (VFPCK) local and Sree Athira) and soil physicochemical and biological properties under organic vs conventional systems in split plot design. Varieties × production systems interaction was not significant for most of the variables. The elite as well as the local varieties responded equally well to both the systems with average corm yields of 27.72 tonnes/ha under organic and 28.55 tonnes/ha under conventional practice. The var. Gajendra responded well to organic management producing higher yield (+10%). The other varieties had lower yield losses (-2.5-15.0%) under the organic system. The corms of the varieties had slightly higher dry matter, sugar, P, K and Fe contents under organic system. The varieties also exerted similar effects on soil physicochemical and biological properties, when tested under organic and conventional management. However, Gajendra and Sree Padma effected significantly higher organic C status under organic management due to greater biomass addition on account of their innate robust plant type. In general, there was significant improvement in soil pH and bacterial count, slight lowering of bulk density and particle density, improvement in water holding capacity, secondary and micronutrient status, N fixers and dehydrogenase enzyme activity in the organic system. Key words: Adaptation, Elephant foot yam, Organic agriculture, Quality, Varieties, Yield Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is an important tropical tuber crop popular as a food security crop and a remunerative cash crop. Its corms are rich in starch, which is used as a vegetable having high nutritive value, good taste and cooking quality besides having medicinal values. The corms also contain moderate amounts of protein, Ca and vitamin C. The crop has a high production potential. It has great scope for commercial exploitation as a medicinal crop in pharmacological industry due to the presence of various nutraceuticals and the corms find wider use in traditional ayurvedic preparations for the treatment of inflammation, piles and gastrointestinal disorders (Regu et al. 1999). Organic farming was found to be an eco-friendly management strategy in elephant foot yam for sustainable yield of quality tubers and higher profit besides maintaining soil health. Technologies for organic production of elephant foot yam was standardized (Suja et al. 2010, 2010a, 2012b, Suja 2013). One of the biggest challenges that organic farmers face is identification of locally adapted crop varieties that can thrive under organic management conditions in the absence of chemical supports (Maddox 2015). It is estimated that more than 95% of organic production is based on crop varieties that were bred for the conventional high-input sector (van Bueren et al. 2011), which lack important traits required under organic and low-input production conditions (van Bueren et al. 2002, Murphy et al. 2007, Wolfe et al. 2008). Hence, the conventional varieties are not ideal for the diverse growing conditions found on organic farms (Maddox 2015). Experimental evidences on the adaptation of varieties developed for chemical intensive system to organic management is also lacking (Fagnano et al. 2012). Presently in elephant foot yam, we have both improved 1, 3 Principal Scientist (e mail: sujagin@yahoo.com, e mail: byju_g@yahoo.com), Division of Crop Production, 2Principal Scientist (e mail: sreejyothi_in@yahoo.com), Division of Crop Utilization. 115 1344 SUJA ET AL. (Gajendra, Sree Padma, Sree Athira) and local varieties suitable for cultivation in the different agro-ecological regions of India. However, little had been documented about the response of varieties to organic farming. Hence, the objectives of the present study were to compare the growth, yield and quality performance of elephant foot yam varieties and soil physico-chemical and biological properties under organic vs conventional management. m. Corm pieces of 500 g with a portion of terminal bud treated with slurry containing cowdung, neem cake and Trichoderma harzianam (5 g/kg seed) were planted in pits of 60 × 60 × 45 cm size. The plant to plant distance was 90 cm. Cultural practices followed were in accordance with the package of practices of KAU (2002). The crop was planted during March in each year, mainly as rain-fed and harvested after nine months. In organic farming plots, green manure cowpea was sown twice viz., prior to experimentation and immediately after planting elephant foot yam in between the pits and green matter was incorporated at 50% flowering stage. The quantity of green matter incorporated was 22.25 tonnes/ha and 21.50 tonnes/ha in 2010 and 2011, respectively. Growth characters such as plant height, leaf spread and girth of pseudostem were measured from three plants at 3, 6 and 9 months after planting (MAP), mean values computed and expressed in cms. Corms from the net plot were harvested and corm yield was expressed in t/ha. Proximate analyses of tubers for dry matter, starch, crude protein, total sugars, ash and fibre (AOAC 1980) and mineral composition of tubers, viz. P, K, Ca, Mg, Fe, Mn, Zn and Cu contents (Piper 1970), chemical parameters of soil viz., organic C, pH, available N, P, K, Ca, Mg, Fe, Mn, Zn and Cu status (Page et. al. 1982), physical characters of the soil such as bulk density, particle density, water holding capacity (WHC) and porosity (Gupta and Dakshinamoorthy 1980), plate count of soil microbes viz. bacteria, fungi, actinomycetes, N fixers and P solubilizers (Timonin 1940) were determined by standard procedures. The analysis of variance of data was done using SAS (2008) by applying analysis of variance technique (ANOVA) for split plot design and pooled analysis of yield data of two years was also done. MATERIALS AND METHODS Field experiments were conducted for two consecutive years (during March-December during 2010 and 2011) at the Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram (8o29’N, 76o57’E, 64 m altitude), India in an acid Ultisol (pH: 5.45). Two crops of green manure cowpea was raised and incorporated during 2009-2010 prior to the experimentation. In general, the fertility status of the soil was low for N (166.84 kg/ha) and high for organic C, available P and K (1.39%, 296.07 and 368.43 kg/ha, respectively). The site experiences a typical humid tropical climate. The mean annual rainfall was 1958.70 mm, maximum and minimum temperatures were 32.10 and 25.70oC, respectively, and relative humidity was 76.50%. Five varieties (Peerumade local, Gajendra, Sree Padma, Vegetable and Fruit Promotion Council Keralam (VFPCK) local and Sree Athira) of elephant foot yam were evaluated under conventional and organic systems in split plot design. A brief description of varieties is given in Table 1. Varieties were assigned to main plots and production systems to sub plots. The treatment combinations were replicated thrice. In the organic practice, the field validated organic production technology, farmyard manure (FYM) (cowdung + neem cake mixture (10:1) inoculated with Trichoderma harzianum @ 36 tonnes/ha + green manuring to generate 20-25 tonnes/ ha green matter in 45-60 days + neem cake @ 1 tonnes/ ha+ ash @ 3 tonnes/ha) was advocated. In conventional practice, FYM @ 25 tonnes/ha+ NPK @ 100:50:150 kg/ha (Package of Practices (POP) recommendation of Kerala Agricultural University (KAU)) was followed. Elephant foot yam was planted in plots of size 4.5 × 4.5 Table 1 [Indian Journal of Agricultural Sciences 86 (10) RESULTS AND DISCUSSION Growth, yield and quality Varietal effect was significant for plant height at all stages and pseudostem girth at 9 MAP. Production systems imparted significant effect on canopy spread at all stages and pseudostem girth at 3 and 9 MAP. Gajendra and Sree Description of the test varieties of elephant foot yam Varieties Pedigree and source Description Peerumade local Local variety procured from Peerumade Development Society, Peerumade, Pothupara, Idukki Selection from local collections of Kovvur, West Godavari district, Andhra Pradesh, released from Vegetable Research Station, Rajendra Nagar, under the aegis of All India Co-ordinated Research Project (AICRP) on Tuber Crops Selection from indigenous germplasm collection from Wyanad, Kerala, released by ICAR-CTCRI, Thiruvananthapuram Local variety obtained from Vegetable and Fruit Promotion Council Keralam Hybrid selection released from ICAR-CTCRI, Thiruvananthapuram Matures in 8-9 months and produces 40-45 t/ha Average yield of 42.00 t/ha, potential yield of 55.00 t/ha, matures by 180-210 days Gajendra Sree Padma VFPCK local Sree Athira Source: (AICRP 2012; CTCRI, 2006). 116 Average yield of 42.00 t/ha, potential yield of 80.20 t/ha , matures within 8-9 months Matures in 8 months and produces 35-40 t/ha Matures in 9-10 months and yields 40.50 t/ ha October 2016] 1345 ELEPHANT FOOT YAM UNDER ORGANIC MANAGEMENT Padma were significantly taller. Conventional practice resulted in significantly greater canopy spread and pseudostem girth (Table 2). The effect of varieties × production systems interaction was not significant. During both the years, the varietal effect was significant. The effects of production systems and varieties × production systems interaction were not significant. In the first year, all the varieties, except Sree Athira, performed well and were on par (28-34 tonnes/ha). During second year, the elite varieties, Gajendra, Sree Padma and Sree Athira performed well (28-30 tonnes/ha) and the locals (Peerumade and VFPCK locals) proved inferior. In both the years of experimentation, yield under organic farming (28.23, 27.21 tonnes/ha respectively, during the years) was on a par with that of conventional practice (28.55, 28.56 tonnes/ha respectively). Corm yield in the individual years as well as the mean showed that the elite as well as the local varieties responded equally well to both the practices with average corm yields of 27.72 tonnes/ha under organic and 28.55 tonnes/ha under conventional practice (Fig 1 and Table 3). This indicates that both elite and local varieties exhibited similar abilities to source nutrients and put down roots, contrary to the hypothesis that chemicals were easy to access. Though the interaction, varieties × production systems was not significant according to ANOVA, a different behavior of the varieties was identifiable with either higher yield, for Gajendra (+10%) or lower yield losses (–15 % for VFPCK local, 2.5-5.0 % for others) under the organic system, as compared to the conventional one. This suggests that elite varieties, especially Gajendra, may be more suitable for organic farming and confirms the importance of genotype selection for adaptability to organic farming. The effect of varieties, production systems and varieties × production systems was not significant for most of the tuber quality traits. The corms of Sree Athira had significantly higher crude protein contents and the locals had appreciably higher crude fibre contents (Table 4). The biochemical and mineral contents of organic corms were on par with that of conventional corms. However, the conventional corms had significantly higher Mn content. Organic corms had slightly higher dry matter, sugar, P, K and Fe contents (Table 5). Similar results of higher levels of K were observed in organic tomatoes (Pieper and Barrett 2008), organic elephant foot yam and yams (Suja et al. 2012a, 2012b, Suja 2013, Suja and Sreekumar 2014) and inorganic fertilizer treatment was found to significantly enhance the content of Mn in strawberry fruits (Hargreaves et. al. 2008) and elephant foot yam (Suja et al. 2012a, 2012b, Suja 2013). Table 2 Growth performance of elephant foot yam varieties under organic vs conventional management (mean of two years) Varieties/Production systems Plant height (cm) Canopy spread (cm) Pseudostem girth (cm) 3 MAP 6 MAP 9 MAP 3 MAP 6 MAP 9 MAP 3 MAP 6 MAP 9 MAP Varieties Peerumade local Gajendra Sree Padma VFPCK local Sree Athira CD (P=0.05) 34.16 49.16 44.27 32.89 39.05 7.548 33.94 49.33 40.89 32.83 37.06 8.385 55.00 66.20 65.60 50.60 52.70 11.14 86.70 86.90 90.20 85.70 88.80 NS 93.30 94.40 100.40 92.70 93.60 NS 79.90 87.60 91.70 75.70 78.70 NS 12.64 12.69 13.39 12.30 13.39 NS 14.39 15.61 15.03 13.50 14.50 NS 10.28 12.44 12.17 8.22 9.28 2.701 Production systems Conventional Organic CD (P=0.05) 39.51 40.31 NS 38.47 39.16 NS 59.50 56.60 NS 92.00 83.30 6.02 98.40 91.40 5.55 86.50 78.90 6.84 13.45 12.31 0.636 14.98 14.23 NS 11.16 9.80 1.25 MAP- Months after planting. 40 40 35 Con 35 Org Corm yield (t/ha) Corm yield (t/ha) Con Org 30 30 25 20 15 25 20 15 10 10 5 5 0 0 2010 2011 2010 2011 2010 2011 2010 2011 2010 2011 Varieties 2010- 2011- 2010- 2011- 2010- 2011- 2010- 2011- 2010- 20112011 2012 2011 2012 2011 2012 2011 2012 2011 2012 Varieties Fig 1 Response of varieties of elephant foot yam to organic vs conventional management during the period of study 117 1346 Table 6 Physical properties of soil under organic vs conventional management after the experimentation Soil properties Physical properties of the soil The varietal effect on the physical properties of the soil was on par. The varieties × production systems effect Table 3 Production systems Yield response (tonnes/ha) of elephant foot yam varieties to organic farming (Mean of two years) Varieties/Production systems Conventional Organic Mean of varieties Peerumade local Gajendra Sree Padma VFPCK local Sree Athira Mean of production systems CD (P=0.05) 27.42 30.75 30.31 30.69 23.61 28.55 26.71 33.69 28.85 26.09 23.26 27.72 27.07 32.22 29.59 28.39 23.43 Table 4 [Indian Journal of Agricultural Sciences 86 (10) SUJA ET AL. Conventional Organic CD (P=0.05) Varieties Peerumade local Gajendra Sree Padma VFPCK local Sree Athira CD (P=0.05) Varieties: 2.826; Production systems: NS; Varieties × production systems: NS 13.63 2.13 2.08 3.98 21.03 23.24 19.84 24.75 NS 13.64 15.48 12.55 16.19 NS 1.94 1.99 2.26 2.87 0.469 2.05 2.16 1.91 2.117 NS 4.43 1.20 4.07 1.07 4.72 1.50 3.97 1.10 NS 0.224 Production systems Conventional 21.87 Organic 22.03 CD (P=0.05) NS 14.33 14.26 NS 2.27 2.21 NS 1.98 2.14 NS 4.47 1.26 3.99 1.26 1.100 NS Table 5 Varieties/Production systems Varieties Peerumade local Gajendra Sree Padma VFPCK local Sree Athira CD (P=0.05) Production systems Conventional Organic CD (P=0.05) 1.640 1.615 NS 2.435 2.401 NS 12.55 13.33 NS 32.65 32.47 NS Chemical properties of the soil The effect of varieties, production systems and varieties × production systems was not significant during the first year. The pH, organic C, available N, P and K status of organic and conventional plots was almost the same. Chemical analysis of soil samples at the termination of the experiment indicated that varieties × production systems interaction was not significant, except, organic C and available K status. However, between the systems, organic management resulted in significant improvement in pH (Table 7). Organic C status was significantly higher under organic practice for Gajendra and Sree Padma. This may be mainly due to greater biomass addition on account of their inherent robust plant type (Table 2). Available K status was significantly highest in conventional practice and lowest in organic practice under Sree Athira. Elephant foot yam is a heavy K consuming crop and responds well to easily available nutrient sources of K. The status of secondary and micronutrients, Ca, Mg, Fe, Mn and Zn was also not significantly influenced by the Dry Starch Crude Total Ash Fibre matter (% FW protein sugars (% (% (%) basis) (% FW (% FW DW DW basis) basis) basis) basis) 20.88 1.771 1.744 NS was also not significant. Though there was slight reduction of bulk density and particle density and improvement in water holding capacity of the soil under organic management in all the varieties, the effect of production systems was also not significant (Table 6). This is similar to the earlier reports in elephant foot yam, yams and taro (Suja et al. 2012a, 2012b, Suja 2013, 2015, Suja and Sreekumar 2014). Effect of varieties and production systems on biochemical constituents of corms Varieties/ Production systems Dry bulk Wet bulk Particle Water Porosity density density density holding (%) (g/cm3) (g/cm3) (g/cm3) capacity (%) 1.45 Effect of varieties and production systems on mineral content (mg/100g) of corms P K Ca Mg Fe Mn Zn Cu 230.60 215.80 197.20 212.30 225.50 NS 1623 1581 1416 1777 1741 NS 160.20 149.00 149.80 159.60 164.90 NS 65.08 63.67 64.67 65.08 63.42 NS 60.80 56.60 71.00 72.20 71.20 NS 4.90 4.91 4.97 5.01 4.12 NS 8.62 7.82 6.87 7.07 7.50 NS 0.93 0.91 0.72 0.85 0.80 NS 207.40 225.20 NS 1587 1669 NS 157.00 156.40 NS 64.13 64.63 NS 64.40 68.40 NS 5.33 4.23 0.584 7.39 7.76 NS 0.88 0.81 NS 118 October 2016] varieties, production systems and varieties × production systems interaction (Table 8). Available Cu content was significantly influenced by varieties × production systems interaction. Though no definite trend was observed, Cu content was higher in conventional practice for most of the varieties especially, Gajendra and Sree Padma. However, exchangeable Ca, Mg, Fe and Zn contents were slightly higher in organic plots. Similar results have been reported earlier under organic management of yams and aroids (Suja et al. 2012a, Suja 2013, 2015, Suja and Sreekumar 2014). Table 7 Laxities Peerumade local Conv Peerumade local Org Gajendra Conv Gajendra Org Sree Padma Conv Sree Padma Org VFPCK Conv VFPCK Org Sree Athira Conv Sree Athira Org CD (P=0.05) Microbial count of the soil and soil enzyme activity Production systems imparted significant effect on bacterial count. Varieties × production systems interaction effect was not significant for biological properties of the soil. Bacterial count in the soil was significantly higher in organic plots. The population of fungi, actinomycetes, P solubilizers, N fixers and dehydrogenase enzyme activity was almost same in both the production systems (Tables 9 and 10). However, the dehydrogenase enzyme activity and the count of N fixers were slightly higher in organic plots. Dehydrogenase, the respiratory enzyme and integral part of all soil organisms, is the most commonly used indicator of biological activity in soils. The higher dehydrogenase activity in organic plots might be due to higher oxidation or decomposition of organic matter due to addition of large quantities of organic sources of nutrients (FYM, green manure, neem cake etc.) to supplement the nutrient requirement. Suja and Sreekumar (2014) also observed similar results in yams. The conventional practice favored the acid phosphatase activities slightly (Table 9), which may be due to addition of synthetic fertilizers. It can be concluded that both the improved and local pH Organic Available Available Available C (%) N P K (kg/ha) (kg/ha) (kg/ha) 4.591 1.522 83.10 74.10 418 4.536 1.135 80.60 70.40 374 4.587 4.757 4.481 4.896 4.505 4.718 4.732 4.689 NS 1.099 1.597 1.008 1.549 0.946 1.006 1.454 1.151 0.439 78.30 77.70 80.10 79.50 81.80 70.80 77.20 93.40 NS 70.50 88.00 74.10 74.10 63.00 90.00 90.20 82.90 NS 428 408 400 440 462 457 556 328 193.1 Production systems Conventional 4.58 1.21 Organic 4.72 1.29 CD (P=0.05) 0.134 NS 80.10 80.40 NS 74.40 81.10 NS 453 401 NS Table 8 Biological properties of the soil Effect of production systems and varieties × production systems interaction on major soil chemical properties in elephant foot yam at the end of experimentation Varieties × Production systems 1347 ELEPHANT FOOT YAM UNDER ORGANIC MANAGEMENT Table 9 Effect of production systems on soil microbial activityat the end of experimentation Production systems Bacteria Fungi Actino- P solubi- N fixers (×107cfu/ (×106cfu/ mycetes lizers (×105 g soil) g soil) (×105cfu/ (×106cfu/ cfu/g g soil) g soil) soil) Conventional Organic CD (P=0.05) 22 31 8.35 5 6 NS 24 22 NS 5 5 NS 165 182 NS Effect of production systems and varieties × production systems interaction on secondary and micronutrient status of soil at the end of experimentation Varieties × Production systems Exchangeable Ca (meq/100g) Exchangeable Available Fe Mg (meq/100g) (ppm) Laxities Peerumade local Conv Peerumade local Org Gajendra Conv Gajendra Org Sree Padma Conv Sree Padma Org VFPCK Conv VFPCK Org Sree Athira Conv Sree Athira Org CD (P=0.05) 0.712 1.119 0.779 0.815 0.959 0.823 0.944 0.839 0.843 0.903 NS 0.332 0.415 0.397 0.386 0.401 0.417 0.406 0.375 0.429 0.384 NS 32.22 35.99 32.73 31.98 34.73 32.42 34.95 33.42 32.40 34.63 NS 7.04 8.29 8.02 7.54 9.99 8.99 8.67 7.20 8.59 7.07 NS 5.55 6.10 5.80 5.53 6.04 5.84 5.82 5.84 5.86 5.98 NS 0.41 0.59 0.54 0.33 0.75 0.33 0.44 0.35 0.37 0.63 0.255 Production systems Conventional Organic CD (P=0.05) 0.85 0.90 NS 0.39 0.40 NS 33.41 33.69 NS 8.46 8.02 NS 5.82 5.86 NS 0.50 0.45 NS 119 Available Mn (ppm) Available Zn Available Cu (ppm) (ppm) 1348 SUJA ET AL. Table 10 Effect of production systems on soil enzyme activity at the end of experimentation Production systems Conventional Organic CD (P=0.05) Dehydrogenase enzyme (mg TPF formed/g soil/h) Acid phosphatase (µg para nitro phenol released/ g soil/h) Urease (mg urea formed/g soil/h) 1.323 1.625 NS 1.42 1.23 NS 1.99 1.99 NS [Indian Journal of Agricultural Sciences 86 (10) Indian Agricultural Research Institute, New Delhi. Hargreaves J C, Adl M S, Warman P R and Rupasinghe H P V. 2008. The effects of organic and conventional nutrient amendments on strawberry cultivation: Fruit yield and quality. Journal of the Science of Food and Agriculture 88: 2 669–75. KAU. 2002. Package of Practices Recommendations: Crops. Directorate of Extension, Kerala Agricultural University, Mannuthy, Thrissur, pp 49–53. Maddox N. 2015. Back to basics: Breeding plants for organic agriculture. Crops Soils Agronomy News 60(3): 4–8. Murphy K M, Campbell K G, Lyon S R and Jones S S. 2007. 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