Volume 8, Issue 1, January – 2023 International Journal of Innovative Science and Research Technology

ISSN No:-2456-2165

Impact of Organic and Inorganic Fertilizers on

Microbial Populations at Various Altitudes of
Nepal in Paddy Field Soil Systems
Saraswoti Kandel1* Pratiksha Sharma2
1 2
National Soil Science Research Centre National Plant Pathology Research Centre
Nepal Agriculture Research Council (NARC) National Agricultural Research Centre (NARC)
Khumaltar, Lalitpur, Nepal Khumaltar, Lalitpur, Nepal

Suraj Chaudhary3
3
Central Department of Biotechnology
Tribhuvan University (TU)
Kritipur, Nepal

Abstract:- Soil microbes are important in processes such meet the needs of an expanding population (Zhang et al.
as soil aggregate formation, nitrogen cycling, compound 2019). Thus, for sustainable agricultural intensification, it's
breakdown, and other transformations. Understanding crucial to understand how microbes react to chemical and
how microorganisms react to chemical and organic organic fertilizers.
fertilizers is critical for long-term agricultural
intensification. Soil samples were collected from three Numerous research has revealed that fertilization
distinct ecological sites of Nepal including terai management has a significant impact on the biomass of soil
(Parwanipur), mid-hills (Pakhribas), and high hills microorganisms and community structure (Liu et al. 2021).
(Jumla) during winter seasons for period of three years The functionality and quality of soils may change as a result
2017, 2018, and 2019. Sandy loam soils of Agricultural of repeated fertilization because it alters the fertility and
Research Farm, NARC, were used to assess the effects of availability of nutrients, which can modify the physical,
compost and inorganic fertilizers on microbial dynamics in chemical, and biological characteristics of the soil. Microbes
the continuous rice wheat cropping system. The results are a very sensitive part of agricultural
showed that the farmyard manure-treated plot had the ecosystems. Management techniques, such as the addition of
highest microbial population counts (fungal and bacterial) manure and mineral fertilizer, may promote the growth of
in all years, followed by the inorganically treated plot and some microbes while restricting the growth of others (Luo et
the control at all locations. The Pakhribas location had the al. 2015; de Vries et al. 2006). According to some research,
highest bacterial and fungal population across all long-term chemical fertilization boosted microbial biomass
treatments. A significant change in fungal population was and activity without significantly altering bacterial community
observed between treatments and experimental sites. structure. However, another study found that it reduced the
Across all treatments, the Jumla location had the lowest diversity of arbuscular mycorrhizal fungi (Su et al. 2015).
fungus population and Pakhribas had the highest. According to a study, soil acidity caused by fertilizer N
application reduced the diversity and/or the number of soil
Keywords:- Altitude, Bacterial Population, Farmyard microorganisms. Generally, the use of chemical N fertilizer
Manure, Fungal Population, NPK. encouraged the growth of fungus (Mujiya and Supriyadi
1970; Zhang et al. 2019).
I. INTRODUCTION
Previous research has demonstrated variations in soil
Agro ecosystems rely on soil microorganisms. They play microbial community structure, abundance, and enzyme
critical roles in processes such as the formation of soil activity along a number of elevational gradients (Siles et al.
aggregates, the formation of soil humus, the cycling of 2016; Singh et al. 2012; Wang et al. 2015). Abiotic
nutrients, the breakdown of different compounds, and other (temperature, precipitation, air composition, etc.) and biotic
transformations (Luo et al. 2015; Wu et al. 2011). The components experience considerable environmental gradients
biomass, diversity, and abundance of soil microorganisms are as altitude rises (vegetation, biodiversity and composition). As
potential indicators of soil quality, which are linked to soil a result, plant communities along an altitudinal gradient may
productivity, crop development, and yield, and can reveal the differ in terms of soil properties and microbial populations
biological fertility, health, and vitality of the soil(Bending et (Ma et al., 2004; Xu et al., 2014). Due to the harsher
al. 2004). The most typical method of managing agricultural environment at higher altitudes, there was a reported increase
soils is fertilization. The main purpose of both organic and in the ratio of Gram-negative/Gram-positive bacteria, fungus
inorganic fertilizers is to boost crop yield (Luo et al. 2015). as well as an increase in the relative fraction of culturable
Increased grain production must rely heavily on chemical psychrophilic heterotrophic bacteria (Siles et al. 2016).
fertilizer inputs to overcome nutrient deficiencies if it is to Numerous researchers have noted a decline in microbial

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Volume 8, Issue 1, January – 2023 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
population size, bacterial and fungal diversity (Lipson 2007; D. Enumeration of microbial populations
Schinner and Gstraunthaler 1981), as well as microbial activity The serial dilution plate count method was used to isolate
like respiration rate, microbial biomass, and metabolic and estimate the populations of bacteria and fungi. 10 g of soil
quotient with altitude (Margesin et al. 2009; Niklińska and sample was added to 90 mL of sterile water, and the mixture
Klimek 2007; Schinner and Gstraunthaler 1981). was stirred for a short duration. Then, sterile distilled water
was used to execute a series of dilutions up to 10 -6 in a test
The impact of altitude and organic/inorganic fertilizer on tube. Spread 0.1 mL of the diluted soil suspension from each
soil microorganisms in Nepal's agro ecosystems has received serial dilution on the various media—nutrient agar (NA) for
little attention. The goal of this study was to evaluate the bacteria and potato dextrose agar (PDA) for fungus. The plates
variations in microbial abundance in paddy soil as influenced were incubated for 5-7 days at 25°C for fungi and for 1-2 days
by repeated applications of both organic and inorganic at 30°C for bacteria. Colony forming units were counted after
fertilizer across different altitudes. incubation and expressed as CFUg-1 of soil on a moisture-free
basis.
II. MATERIALS AND METHODS
E. Data analysis
A. Study site The data were analyzed using GraphPad Prism 8.3.0 and
For the study, three distinct ecological sites of Nepal Microsoft excel. Treatment means were compared using
including the terai (Parwanipur), midhills (Pakhribas), and Tukey's test (ANOVA) at 5% levels of significance.
high hills (Jumla) were chosen. The study was conducted for
period of three years 2017, 2018 and 2019. Table 1 shows the III. RESULTS
ecoclimatic characteristics of study sites.
A. Microbial populations at experimental site of Parwanipur
Table 1: Ecoclimatic features of Parwanipur, Pakhribas and There was a significant difference in the bacterial
Jumla study site population between the control and treated plots (Farmyard
Paramete Sites manure and recommended dose of NPK). Figure 1 shows that
r Parwanipu Pakhribas Jumla the bacterial population was highest in the organically treated
r plot and lowest in the control plot throughout the study year.
Latitude 27° 27° 29°16'21.69" There was no significant difference in bacterial population in
4'40.89"N 2'51.35"N N organic manure treatment across different experimental years.
Longitude 84°56'1.25" 87°17'36.38" 82°10'49.17" However, when compared to prior and subsequent years, the
E E E bacterial population was reduced in 2018 with the control and
Elevation 95 m asl 1738m asl 2346m asl recommended dose of NPK treatment. Treatment with the
recommended amount of NPK resulted in a higher bacterial
population when compared to the control treatment. The
B. Experimental design fungal population in paddy fields showed similar trends, with
Soil sample were collected from long term fertility trial the maximum and minimum values recorded in the organic
of different ecological locations, covering terai (Parwanipur), and control plots, respectively (shown in fig 2). The fungal
mid hills (Pakhribas) and high hills (Jumla) after rice harvest population in the organic plot differed significantly from that
and analyzed stastistically for microbial diversity and in the control plot and NPK treatment. Along the trial year, an
abundance at lab in NSSRC, Khumaltar, Lalitpur, Nepal. The increasing trend in fungus population was detected with
effects of continual application of organic manure and NPK organic and inorganic fertilizer treated plots. Variation was
fertilizers in rice wheat rotation at Pakhribas and Parwanipur seen in control plots.
with each plot of a 12(4x3) m2 size and in barley and rice
rotation at Jumla with each plot of 10 (5x2) m2 sizes has been
150000
studied. A randomized complete block design with different Control
Bacterial population

treatments and three replicates was used to set up the

cfu 102/g dry soil

FYM
experiment on each site. For this investigation, only three
treatments were observed including control, NPK fertilizer (at 100000 NPK
the recommended dose), and farmyard manure (6 Mt/hac) for
three-year period (2017, 2018 and 2019) on each different site
during the paddy growing season. 50000

C. Soil sampling
Following harvest, soil samples were collected 0
aseptically from each experimental plot's (0–15 cm) soil depth. 2018 2018 2019
Random soil samples were taken from each plot and Treatments
thoroughly mixed to create a uniform mixture. 250g of the soil
Fig 1: Effect of organic and inorganic fertilizers on bacterial
samples were taken, and they were placed in storage at 4°C for
population at experimental site of Parwanipur.
further study.

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Volume 8, Issue 1, January – 2023 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
C. Microbial population at experimental site of Jumla
15000
Control The bacterial population showed substantial change
across treatments. During 2017, 2018, and 2019, the bacterial
Fungal population
cfu 102/g dry soil

FYM
10000 NPK
population was maximum in organically treated plot and an
increasing trend was also observed (shown in fig 5). Except
for 2017, the control treatment had the lowest bacterial
5000 population. NPK-treated plots had a higher bacterial
population than control plots. The fungus population varied
depending on the treatment (shown in fig 6). Control therapy
0 was observed with the highest fungal population in 2017.
2017 2018 2019 However, organically treated plots had the highest population
Treatments in 2018 and 2019. During 2018 and 2019, a similar fungal
Fig 2: Effect of organic and inorganic fertilizers on fungal population was reported in control plots and NPK treated
population at experimental site of Parwanipur. plots. In 2019, there was a significant increase in the fungus
population in organically treated fields.
B. Microbial population at experimental site of Pakhribas
There was a substantial difference in bacterial population 250000
between organically treated plots and other plots. Throughout Control

Bacterial population
the entire study period, the bacterial population was highest in 200000 FYM

cfu 10/g dry soil

the organically treated plots (shown in fig 3). During 2017 and NPK
2019, the bacterial population was identical in control plots 150000
and suggested dose NPK treated plots. However, in 2018,
there was some variance. In 2018, all treatments resulted in a 100000
decrease in the bacterial population. Variation in fungal
50000
population was detected at the Pakhribas experimental site
with different treatments. During 2017 and 2018, a 0
higher fungal population was reported in the control plot 2017 2018 2019
(shown in fig 4). In 2019, organically treated plots had the Treatments
highest fungus population. Also in 2019, comparable findings
were seen in both control and NPK-treated plots. Fig 5: Effect of organic and inorganic fertilizers on bacterial
population at experimental site of Jumla.
60000
Control
1500
Bacterial population

Control
cfu 102/g dry soil

FYM
Fungal population

40000 NPK
cfu 102/g dry soil

FYM
1000 NPK
20000

500
0
2017 2018 2019
Treatments 0
2017 2018 2019
Fig 3: Effect of organic and inorganic fertilizers on bacterial
Treatments
population at experimental site of Pakhribas.
Fig 6: Effect of organic and inorganic fertilizers on fungal
25000
population at experimental site of Jumla.
Control
The bacterial population varied throughout the three
Fungal population
cfu 102/g dry soil

20000 FYM
NPK experimental sites: Parwanipur, Pakhribas, and Jumla.
15000 Bacterial populations were substantially lower in Jumla than
in Pakhribas and Parwanipur. In all treatments, the Pakhribas
10000
study location had the highest bacterial population. The
5000 Pakhribas research site likewise had the highest fungus
population. When compared to other study locations; the
0 fungal population was lowest at Jumla. In all treatments, the
2017 2018 2019
bacterial and fungal populations were significantly greater in
Treatments Parwanipur than in Jumla.
Fig 4: Effect of organic and inorganic fertilizers on fungal
population at experimental site of Pakhribas.

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Volume 8, Issue 1, January – 2023 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
environmental stress, such as low air pressure and cold
IV. DISCUSSION climate, adverse nutritional circumstances, and altered field
vegetation, all of which can influence microbial communities
The present experiment revealed that the soil microbial and activities(Ma et al. 2004).However, research has
population increased in organically supplemented plots when discovered that soil bacteria may not have tight elevational
compared to inorganic and control plots. This could be due to limits as long as the environment supplies some organic matter
the introduction of organic amendments, which may have a and at least brief intervals of water. At an elevation range of
significant impact on the size and activity of the microbial 900-1900m a.s.l., Djukic et al.(2010) discovered no consistent
population. According to a research, organic amendments that elevational trend in entire microbial community size, whereas
increase the organic carbon and C/N ratio have a substantial fungal biomass decreased with increasing elevation. Our
impact on the structure of bacteria and eukaryotic results are consistent with these findings.
communities (Marschner, Kandeler, and Marschner 2003).
The manure soils also provided a lot of easily available C, Given that long-term agricultural usage of inorganic
which resulted in a more diversified and dynamic microbial fertilizers unavoidably reduces microbial activity, Ge et al.
ecology than in inorganically fertilized soil(Kirchner, (2010) urge that a combination of organic manure and
Wollum, and King 1993). Joergensen et al. (2010) inorganic fertilizers be considered based on the balance of crop
demonstrated that the long-term application of farmyard demand and soil availability of accessible nutrients. Manna et
manure in conjunction with organic farming practices resulted al. (2007) demonstrated that a NPK fertilizer, either alone or
in an increase in bacterial residue accumulation. When in combination with manure application, had a positive effect
compared to mineral fertilizers, Murphy et al., (2007) on crop yields in a cereal-based cropping system, and that the
demonstrated that organic material such as compost or manure combination of NPK fertilizer and manure had a significant
decomposes slowly in the soil and the continual release of impact on soil fertility improvement.
nutrients can support the microbial biomass population for
extended periods of time. Our findings are consistent with the V. CONCLUSIONS
findings of this investigation. In general, the amount and
quality of organic material added to soils are the most Organic and inorganic treatments had varied effects on
important elements in influencing the number of various the rhizosphere microbial community. When compared to
microbial groups and the activity of microorganisms involved inorganic treatment, the administration of farmyard manure
in nutrient cycling (Diacono and Montemurro 2010). resulted in a more pronounced growth of the microbial
population. Furthermore, across multiple study sites at varying
Increased microbial abundance was observed with elevations, farmyard manure exhibited a higher microbial
inorganic fertilization in all experimental sites Parwanipur, population than inorganic fertilizer. Thus, farmyard manure
Pakhribas and Jumla. Kang et al., (2005) showed an increase and inorganic fertilizers can be used alone or in combination
in bacterial population in response to chemical fertilizers, for microbial abundance enhancement.
which might be attributable to the soil's improved nutritional
status. Several studies have discovered that bacterial ACKNOWLEDGMENT
populations and abundance are relatively unresponsive to
long-term inorganic fertilization (Wu et al. 2011). Long-term We would like to express our sincere gratitude to the
application of mineral fertilizers may enhance soil N and P National Soil Science Research Centre, NARC, Lalitpur,
content but reduce soil pH (Ge et al. 2010).The pH of the soil Nepal for their technical and financial support to have this
can have a big impact on microbial biomass. The decrease in manuscript.
microbial biomass can be detected with an increase or decrease
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