Effect of Long-term Nutrient Management on Microbial Abundance, Resistance and Resilience in an Alfisol under Abiotic Stresses
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Date
2019
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DIVISION OF SOIL SCIENCE AND AGRICULTURAL CHEMISTRY ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Information on soil resilience and resistant is of paramount importance for managing
various abiotic stresses as anticipated under changing scenario of climate change. Longterm manuring and fertilization experiment could be considered as appropriate to study
resistance and resilience in soil. In the the present investigation, abundance of microbial
groups, their resistance and resilience of soil microbial function against abiotic stresses
and relationships of resistance and resilience with abundance of microbial groups were
studied. To accomplish these objectives, soil samples (0-15 cm depth) were collected
from seven selected treatments (control, N, NP, NPK, NPK+hand weeding, NPK+FYM
& NPK+Lime) under soybean (Glycine max) crop of in the kharif season of 2018 from
the ongoing Long-term Fertiliser Experiment (LTFE) continuing at experimental farm of
Birsa Agricultural University, Ranchi since the year of 1972. The samples were analysed
for soil enzymes activities (dehydrogenase, fluorescein diacetate & β-glucosidase),
organic carbon, microbial biomass carbon, substrate induced respiration and different
microbial groups immediately after sampling (0 day). Soil samples were exposed to two
different stress i.e. (i) heat (48 °C temperature for 24 h) (ii) moisture (air dry soil
moisture content 1.2%) and incubated for 60 days at 28 ºC with optimal moisture content
(2/3rd water holding capacity). Above mentioned soil parameters were analysed at 1, 15,
30 and 60 day(s) after stress. The results indicated that, long-term manuring and
fertilization significantly affected enzymes activities, organic carbon, microbial biomass
carbon, substrate induced respiration, metabolic quotient, and microbial groups (bacteria,
fungi, Actinomycetes, and ammonia oxidising bacteria). Among the selected seven
treatments, balanced fertilization with NPK (i.e., 100% NPK based on initial soil test
values) + FYM (farmyard manure) showed the highest values of the above-mentioned
soil parameters, while the control treatment consistently recorded the lowest values. By
and large, balanced application of NPK along with hand weeding recorded significantly
higher values of soil parameters over balanced application of NPK with weedicide.
Abiotic stresses significantly decreased the enzymes activities, microbial biomass carbon,
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substrate induced soil respiration (SIR) and different microbial groups. The magnitude of
reduction varied between 30 - 84% for heat stress with corresponding value 25-88 in case
of moisture stress. The extent of reduction of different soil properties due to stress was
highest in N alone (100% N) and NP (100% NP) treatments. Interestingly, continuous
hand weeding with balanced fertilization helped in build-up of higher resistance and
resilience of soil biological parameters as compared to weedicide with balanced fertilizer
application. Among the biochemical parameters, highest resistance index was observed
with SIR, whereas, resilience of SIR ranged from 0.13 to 0.96 and –0.25 to 0.94 under
heat and moisture stress, respectively. Dehydrogenase activity proved to be a good
indicator of soil abiotic stress as had been least resilient against heat and moisture stress
as compared to other soil enzymes. Among the soil microorganisms, resistance and
resilience of ammonia oxidising bacteria was lowest, while fungi and actinomycetes were
at par and higher than those of population density of bacteria. Moisture stress (drought) is
more detrimental for soil biological functions than heat stress. Resistance index of
dehydrogenase activity was more consistently associated with initial level of bacterial
(r2=0.45) and AOB (r2=0.45) than Actinomycetes and fungi population under stress.
However, under similar abiotic stress, resilience index of dehydrogenase activity at 15th
day was correlated well with actinomycetes (r2=0.80) and bacterial (r2=0.77) population
in soil. It can be concluded that, application of farmyard manure with balanced NPK was
the most effective in improving the biochemical and microbial population as well as
resistance and resilience of capacity of biological functions in soil against the heat and
moisture stress.
Key words: soil function, abiotic stress, soil microbes, manuring and fertilization
Description
T-10145
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