Long-term Impact of Zero Tillage and Residue Retention on Soil Nutrients and Microbial Biomass in a Maize-Mustard Cropping System

The objective of this study was to evaluate and compare different cropping systems and tillage practices, specifically focusing on the maize (Zea mays L.)-mustard (Brassica juncea L.) cropping system. The field experiment on maize (Zea mays L.)-mustard (Brassica juncea L.) cropping system commenced in monsoon 2010 at ICAR-IARI, New Delhi. Eight treatments were evaluated in a randomized block design, comprising four double cropping ZT (zero till) and two triple cropping ZT systems with or without crops residue retention along with two conventional till systems (control) [T1: ZTMZ-ZTM; T2: ZTMZ+BM-ZTM; T3: ZTMZ(+R)-ZTM(+R); T4: ZTMZ(+R)+BM-ZTM(+R); T5: ZTMZ-ZTM-ZTSMB; T6: ZTMZ(+R)-ZTM(+R)-ZTSMB(+R); T7: CTMZ-ZTM; T8: CTMZ-CTM] with three replications. Result showed that highest mineralizable nitrogen (388 kg ha-1) was found in T6 treatment (in 0-5 cm soil layer) whereas T8 treatment recorded the lowest mineralisable N (297 kg ha-1). ZTMZ(+R)-ZTM(+R)-ZTSMB(+R) treatment obtained a significant increase (81.3%) in Olsen extractable P over CTMZ-CTM treatment. MBP was observed to be maximum in T6 treatment (10.1 mg kg-1) whereas lowest values were recorded in T8 treatment (2.67 mg kg-1) in the upper layer. Therefore, under CA, utilization of microorganisms to increase the availability of P in soil is an attractive proposition for developing a more sustainable agriculture. This is relevant to the high-input production systems of the developed world, and also to developing countries where access to mineral fertilizers is restricted, which will give better results and outputs in future by giving easily available inputs without harming the environment and conserving soil fertility for future generations.