Biological soil health with conventional and qPCR based indicators under conservation agriculture based rice-wheat cropping system in Indo-Gangetic Plain

Conservation agriculture (CA) entails resource sustainability, crop productivity and climate benefits. We assessed biological soil health index (BSHI) using both conventional and state-of-the-art indicators for a long-term rice wheat system under a regime of CA-practices in Indo-Gangetic Plains (IGP). The practices include zero till direct seeded rice (ZTDSR)-zero till wheat (ZTW), ZTDSR + wheat residue (WR)-ZTW + rice residue (RR), ZTDSR + WR + sesbania brown manuring (SBM)-ZTW + RR, ZTDSR-ZTW-zero till mungbean (ZTMB), ZTDSR + mungbean residue (MR)-ZTW + RR-ZTMB + WR, transplanted rice (TPR)-conventional till wheat (CTW)-conventional till mungbean (CTMB). Collected soil samples (0-5 cm depth) were analysed for 8 labile organic carbon pools, 8 soil enzyme activities, population of 7 microbes viz., bacteria, fungi and actinomycetes, and two microbial functions. Further, abundance of different phylogenetic groups and nutrient cycling genes was quantified by molecular based qPCR technique. In general, triple/double ZT + crop residues caused an increase in most of the pools of carbon, enzymes, and microbial population including qPCR-led genes in soils. Specifically, inclusion of mungbean residues in triple ZT and sesbania brown manuring in double ZT improved nifH gene abundance over other double and triple ZT treatments. Of the analysed parameters, beta-glucosidase, Bacterial amoA, Archaeal 16S rRNA, Bacteroidetes 16S rRNA, Bacterial 16S rRNA, and mineralizable C were screened out as the key indicators of BSHI; its value was maximised under triple ZT with residues (ZTDSR + MR-ZTW + RR-ZTMB + WR) treatment. Attempt may be made to use the screened indicators for assessment of BSHI and upscale the identified practice for rice-wheat system in IGP.

Automated summary

This study assessed the impact of conservation agriculture on the biological soil health index in a rice-wheat system in the Indo-Gangetic Plains. The results showed that zero till direct seeded rice and crop residue incorporation could improve soil organic carbon, enzyme activities, and microbial population. Specifically, the inclusion of mungbean residues and sesbania brown manuring significantly increased the abundance of the nifH gene in the soil.