Tillage effects on soil microbial biomass in a rainfed agricultural system of northeast India

In an agricultural system, tillage intensity can influence soil biological properties and relevant soil processes including C sequestration. Microbial biomass often responds quickly to changes in soil management and is known to be an indicator of soil quality. A field study was conducted from 2006 to 2007 in the rainfed agricultural system of northeast India with variedly tilled implements (indigenous spade, Country Plough, Bose Plough and Mouldboard Plough) to study the latter's effect on soils’ microbial nutrient concentration during different growth phases of Oryzasativa. No-till plot of the study site recorded comparatively higher values for microbial C (498.17 μg g−1) microbial N (71.01 μg g−1) and microbial P (44.50 μg g−1). Three-way factorial ANOVA (duration, tillage type and soil depth) for microbial nutrients too showed significant variation with each of these factors. Total organic C and available P showed significant correlation with microbial biomass C (R2 = 0.6348, n = 120, p < 0.01) and microbial biomass P (R2 = 0.916, n = 120, p < 0.005), respectively while total N showed significant correlation with microbial N (R2 = 0.5952, n = 120, p < 0.01). Thus our results suggest that for the rainfed agricultural systems conservation tillage, especially no-tillage can improve the substrate availability and the microbial nutrient accumulation rate throughout the crop's growing season; the nutrient pool of which can find its dependence on the replenishment of the labile substrate from the bulk organic matter pool.