Changes in soil biology under conservation agriculture based sustainable intensification of cereal systems in Indo-Gangetic Plains

Abstract Continuous rice-wheat (RW) rotation with conventional agronomic practices has resulted in declining factor productivity and degrading soil resources. A farmer's participatory research trial was conducted in Karnal, India to evaluate 8 combinations of cropping systems, tillage, crop establishment method and residue management effects on key soil physico-chemical and biological properties. Treatments (T) 1–4 involved RW and 5–8 maize-wheat (MW) with conventional tillage (CT) and zero tillage (ZT) with (+ R) and without (− R) residue recycling. Residue was either incorporated (R i ) or mulched (R m ). Treatment 1 (RW/CT − R) had the highest bulk density (BD) (1.47 Mg m −3 ) and T8 (MW/ZT + R m ), the lowest (1.34 Mg m −3 ). After 3 years of cropping, soil accumulated more organic C in (a) MW (9.33 Mg ha −1 ) than RW (8.5 Mg ha −1 ), (b) ZT (9.25 Mg ha −1 ) than CT (8.58 Mg ha −1 ), and (c) + R (10.18 Mg ha −1 ) than –R (7.65 Mg ha −1 ). MW system with ZT and residue (T8: MW/ZT + R m ) registered 208, 263, 210 and 48% improvement in soil microbial biomass C (MBC) and N, dehydrogenase activity (DHA) and alkaline phosphatase activity (APA), whereas RW system in T4 (RW/ZT + R m ) registered 83, 81, 44 and 13%, respectively as compared with T1 (RW/CT − R), the business as usual scenario. Treatment 8 (MW/ZT + R m ) recorded the highest microbial population viz. bacteria, fungi and actinomycetes. The most abundant micro-arthropods present in the soil of experimental plot were Collembola, Acari and Protura which varied with treatments. Soil MBC, APA, BD and micro-arthropod population were identified as the key indicators and contributed significantly towards soil quality index (SQI). MW system with ZT and R m (T8) recorded the highest SQI (1.45) followed by T6 (1.34) and the lowest score (0.29) being in T1 (RW/CT − R). The SQI was higher by 90% in MW compared to RW, 22% in ZT compared to CT, and 100% in residue recycling compared with residue removal. System yield was strongly related to key soil quality indicators and also positively correlated with SQI. Longer-term studies are essential to realize maximal effects of improvements in soil health on crop yields.