Rakshit, RajivKUMAR, Abhishek2017-02-172017-02-172016-07http://krishikosh.egranth.ac.in/handle/1/5810001404Soils are increasingly under environmental pressure most often related to the intensification of anthropogenic activities. Given the crucial importance of maintaining soil functions, understanding the response of soil ecosystems to disturbance or environmental change and the resistance and resilience of soil microorganisms is a key challenge. To maintain these crucial soil functions, it is important to know how soil microorganisms respond to disturbance or environmental change. Keeping this hypothesis in view, an incubation experiment was conducted with two objectives 1) To assess the impact of fertilization and nanomaterials on changes in enzyme activities and microbial biomass in relation to heat stress and 2) To estimate the resistance and resilience indices of soils with added fertilizers and nanomaterials. To achieve these objectives, two sets of experiment were conducted: first set represents a system reflecting the impact of long term residue management in soils and the second one is related to the exposure of control soils with nano zinc and nano iron (both at 10 and 40 ppm). Both the systems were exposed to heat stress by putting them at 48°C for 24 hours to quantify their resistance and resilience. Results from permanent plot experiment showed the reduction of enzymatic activity after exposure to heat stress (23-46% in FDA, 11-94% in acid phosphates activity, 32-113% in alkaline phosphatase and 23-39% in dehydrogenase activity). Microbial biomass carbon was increased with the application of organic residues (15-23% increase) than control on 0 day, but after stress there was a decline in the tune of 12-48% (1 day of incubation). Enumeration of microorganisms showed an increase in their count in the integrated treatments. Resistance and resilience indices values showed that application of organics in culmination with inorganic fertilizers improved the resistance and resilience of enzyme activities (extent of recovery). Results from nanomaterial based experiment showed the negative impact of these materials on the soil enzyme activities (27-75% decrease in FDA, 11-63% decrease in acid phosphatase activity, 12-105% decrease in alkaline phosphatase activity, 20-38% decrease in dehydrogenase activity) and other microbial parameters (24-40%decrease in MBC, 21-137% in Pseudomonas count and 4-21% decrease in actinomycetes count at 0 day i.e. fresh sample without exposed to stress. Resistance and resilience pattern showed that the nanomaterial supplemented system had higher resistance than control; whereas the recovery of these systems are slow but improved as reflected after 90 days of incubation.en---Thesis