Temporal changes in biochemical indicators of soil quality in response to tillage, crop residue and green manure management in a rice-wheat system

Abstract

Abstract Soil quality degradation in the last four decades is threatening the sustainability of puddled transplanted rice (Oryza sativa L.) – wheat (Triticum aestivum L.) (RW) system in north-western region of India. Hence comprehensive information on the influence of soil and crop management practices in intensive and nutrient exhausting RW system on soil quality is urgently needed. The present study evaluated the effects of crop residues, green manure and tillage on the changes in soil biochemical properties at different growth stages of wheat after five cycles of RW system. Four main plot treatments in rice included combinations of wheat straw and Sesbania green manure management: (1) PTRWS0, puddled transplanted rice (PTR) with no wheat straw (2) PTRWS25, puddled transplanted rice with 25% anchored wheat stubbles retained (3) PTRWS0 plus green manure (GM), and (4) PTRWS25 plus GM. Three sub-plots treatments in subsequent wheat included (1) CTWRS0, conventional tillage wheat without rice straw (2) ZTWRS0, zero tillage wheat without rice straw and (3) ZTWRS100, ZTW with 100% rice straw retained as surface mulch. The results showed that PTRWS25 plus GM and ZTWRS100 increased significantly all the soil biochemical properties (enzyme activities and glomalin related soil protein concentration) except phenol oxidase and peroxidase activities. The activities of dehydrogenase, β-glucosidase and concentration of easily extractable glomalin and total carbohydrate carbon under ZTWRS100 were 36.8, 24.6, 25.9 and 23.3% higher than CTWRS0. Application of GM and wheat straw retention in previous rice significantly increased grain yield of subsequent wheat crop by 26.5%. The majority of the increases in biochemical properties were higher at vegetative growth (at 40–45 days after sowing) and flowering (at 80–85 days after sowing) stages compared to the initial and at maturity. Principal component analysis identified β-glucosidase, cellulase and phenol oxidase activities as the most sensitive and reliable indicators for assessing soil quality for conservation agriculture based RW system.