Impact of Different Tillage and Residue Retention Practices on Soil Nutrients, Microbial Community Composition and Grain Yield of Malt Barley

Purpose: The primary goal of the study was to understand how different tillage and residue management practices affect soil quality, microbial communities, nutrient availability, and grain yield in barley. Methods: Seven residue retention strategies involving rice-barley-green gram crop rotation and retention of rice residue (RR) at 4 and 6 t ha(- 1), with two sowing practices in rice (reduced tillage-direct seeded and un-puddled transplanted) were studied for their effect on soil nutrients composition, bacterial community structure and abundance including plant growth promoting rhizobacteria (PGPR), lignocellulose degrading bacteria (LDB), and malt barley grain yield. The experiment was performed during 2014-15 to 2017-18 cropping season in complete randomized block design in inceptisol under semi-arid, sub-tropical conditions of North-Western plains zone of India. Samples were taken from 0 to 15 cm soil depth at five different locations of each plot using augur after the 2017-18 barley crop harvest, and processed for soil nutrients profile and 16S rRNA metagenomics using next generation sequencing technique. Data was analyzed using one-way analysis of variance. Results: Out of different macro-nutrients, only nitrogen was significantly high of 110.16 kg ha(- 1) in reduced tillage-direct seeded rice-zero tillage barley, followed by other six treatments, while significantly low of 80.91 kg ha(- 1)in un-puddled transplanted rice-zero tillage barley with RR at 4 t ha(- 1). Comparable grain yields of 4.63, 4.61 and 4.60t ha(- 1) of malt barley were recorded under reduced tillage-direct seeded rice-zero tillage barley with rice residue retention at 6 t ha(- 1), un-puddled transplanted rice-zero tillage barley with rice residue retention at 6 t ha(- 1) and same strategy at 4 t ha(- 1),respectively. Highest abundance of significant bacteria both at class and genus level, PGPR and LDB was under reduced tillage-direct seeded rice-zero tillage barley-rice residue at 6 t ha(- 1) [> 1,60,000 and 70,000 operational taxonomic units (OTUs)], followed by same strategy without RR (> 90,000 and 35,000 OTUs) representing Betaproteobacteria, Alphaproteobacteria, Sphingobacteriia, Gammaproteobacteria, Actinobacteria, Deltaproteobacteria, Clostridia and Acidobacteriaclasses in their decreasing order of abundance. Majority were from phylum Pseudomonadota and Bacteroidota. Conclusion: Rice residue retention both under reduced tillage-direct seeded rice-zero tillage barley and un-puddled transplanted rice-zero tillage barley supported highest grain yield of malt barley along with highest abundance Pseudomonas, Sphingomonas and Chryseobacterium among plant growth promoting bacteria, and Pseudomonas, Streptomyces and Clostridium among rice residue degrading bacteria.