RESUMO
The field experiments were conducted on sandy loam soil at New Delhi, during 2007 and 2008 to investigate the effect of conservation tillage, irrigation regimes (sub-optimal, optimal and supra-optimal water regimes), and integrated nutrient management (INM) practices on soil biological parameters in wheat cultivation. The conservation tillage soils has shown significant (p<0.05) increase in soil respiration (81.1 percent), soil microbial biomass carbon (SMBC) (104 percent) and soil dehydrogenase (DH) (59.2 percent) compared to the conventional tillage soil. Optimum water supply (3-irrigations) enhanced soil respiration over sub-optimum and supra-optimum irrigations by 13.32 percent and 79 percent respectively. Soil dehydrogenase (DH) activity in optimum water regime has also increased by 23.33 percent and 8.18 percent respectively over the other two irrigation regimes. Similarly, SMBC has also increased by 12.14 percent and 27.17 percent respectively in soil with optimum water supply compared to that of sub-optimum and supra-optimum water regime fields. The maximum increase in soil microbial activities is found when sole organic source (50 percent Farm Yard Manure+25 percent biofertilizer+25 percent Green Manure) has been used in combination with the conservation tillage and the optimum water supply. Study demonstrated that microbial activity could be regulated by tillage, water and nitrogen management in the soil in a sustainable manner.