Sharma, SandeepPankaj2021-06-042021-06-042020Pankaj (2020). Temporal biochemical changes under tillage and rice residue management in rice-wheat system (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810169526To maintain agricultural productivity and environmental integrity, it is crucial that soil quality to be improved or maintained. Crop residues are the non-utilized sources of renewable biomass generated in large quantities in agriculture and excess residues are disposed by means of burning. Fourteen treatment combinations of fertilizer dose, tillage and residue management included two main plots treatments of nitrogen (N) application in wheat (1) N75, 75% recommended dose of nitrogen and (2) N100, 100% recommended dose of nitrogen and seven subplot treatments (1) CT-R, 100% rice residue removed- Conventional Tillage (2) RS-R, 100% rice residue removed and sowing with Rotoseeder (3) HS+R50, loose rice residue removed and sowing with happy seeder (4) HS+R100, 100% rice residue retained and sowing with Happy seeder (5) RS+R50, loose removal of rice residue and sowing with Rotoseeder (6) RS+R100, 100% rice residue retained and sowing with Rotoseeder (7) CT+R100, 100% incorporation of rice residue and sowing with drill in wheat. The present study evaluated the effects of N application, tillage and rice residue management practices in wheat on changes in soil enzyme (dehydrongenase, fluorescein diacetate, alkaline phosphatase, β-glucosidase, xylanase, cellulase, polyphenol oxidase, peroxidase) activities, microbial biomass carbon, soil respiration, microbial count (bacteria, fungi, actinomycetes, Agrobacterium, Rhizobium and Azotobactor), quotients (microbial quotient, metabolic quotient and metabolic potential), chemical properties (soil organic carbon and water soluble organic carbon) at different growth stages of wheat during 5th cycle of continuous rice-wheat system. The results showed that integrated use of fertilizer N and residue management practices increased wheat yield, water soluble carbon and soil enzyme activities except polyphenol oxidase and peroxidase as compared to conventional practices (CT – R and RS – R). The majority of enzyme activities were higher at vigorous vegetative growth stage as compared to reproductive growth stage. Soil enzyme activities were significantly and positively correlated with each other, microbial biomass carbon and water soluble carbon except polyphenol oxidase activity, peroxidase activity and metabolic quotient. Principle component analysis (PCA) identified dehydrogenase, soil organic carbon, metabolic potential as the most sensitive indicators for assessing soil quality for conservation agriculture based rice-wheat system in surface soil layer. The present study provided reliable biochemical indicators to monitor the changes in soil biological quality response to conservation agriculture practices in rice-wheat system.EnglishThesis