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The impact of long-term (36-year) application of balanced fertilizers and farmyard manures (FYM) on the abundance of microbial groups (bacteria, fungi, actinomycetes, Pseudomonas, Azotobacter, ammonia-oxidizing bacteria) and their resistance and resilience against heat stress was investigated in a semi-arid Inceptisol at New Delhi, India. Surface soils from selected treatments [control, nitrogen (N), N and phosphorus (P), NP and potassium (K), NPK + FYM] under a maize crop were assessed immediately after sampling (0-day) and at 1, 14, 28, and 56 day(s) after heat stress (48 • C for 24 h). The heat stress significantly reduced the microbial groups by 20 to 80%. Recovery after stress was 60 to 100% within 56 days. Resistance and resilience of fungi and actinomycetes were greater than other groups of organisms. Ammonia-oxidizing bacteria (AOB) were found to be most sensitive with the lowest resistance index. Application of NPK + FYM was most effective in enhancing the resistance and resilience of soil microorganisms against heat stress.

Microbial communities are important for the functioning of the ecosystem, both in relation to direct interactions with the plants and with regard to nutrient and organic matter recycling. A study in field condition was undertaken in Kashmir valley to reveal the effect of various temperate fruit crops viz. apricot, peach, plum and cherry along with a control (no-plantation) on microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP) and dehydrogenase, phosphomonoesterase (acid and alkaline) and urease activities in soil at two different depths (0-20 and 21-40 cm). All the fruit crops showed a sharp decline in microbial biomass and enzyme activities with the increase in soil depth. Each of the four fruit crops showed significant (p<0.05) impact on MBC over the control and the maximum MBC was recorded in plum (1000 mg kg -1 ) and the lowest value was observed in control (457 mg kg -1 ), at the surface layer. Since there is a relationship between MBC and MBN, the similar trend was also observed in MBN as in case of MBC. For MBP, fruit crops showed any significant effect neither on surface soil, nor on subsurface soil layer over control. At the surface layer, unlike microbial biomass the highest dehydrogenase activity was observed in peach (318 µg TPF g soil -1 h -1 ) and the lowest value (166 µg TPF g soil -1 h -1 ) was attained at control plot. Maximum alkaline phosphomonoesterase activity was observed in peach (381 µg PNP g soil -1 h -1 ), although for acid phosphomonoesterase the highest value recorded in apricot (306 µg PNP g soil -1 hr -1 ), at surface soil. A significant positive correlation (p <0.01) was observed amongst MBC, MBN and MBP. Both the phosphomonoesterase activities were significantly (p <0.05) correlated with MBP in soil. It can be concluded that the influence of the studied fruit crops on the soil was not uniform, in terms of the measured parameters.

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