Sharma, SandeepAngmo, Padma2023-12-122023-12-122023Angmo, Padma (2023). Long-term effect of conservation agriculture practices on soil biochemical properties in rice-wheat and maize-wheat systems (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810202775Long-term resource conservation strategies are considered a pre-requisite for improved soil health and ecosystems’ sustainability for cropping systems. The present study quantified the impact of tillage regimes, methods of irrigation, rate of nitrogen and straw return in conventional and conservation agriculture-based rice-wheat and maize-wheat systems on soil enzyme activities, labile soil carbon pools and microbial diversity in earthworm casts and guts. The results revealed that all the extracellular enzyme activities (EEA) were highest at the surface soil layer (0-10 cm) and decreased with an increase in soil layers. Among different growth stages, the maximum tillering stage of wheat and rice, and maize at knee-high stage were registered the highest EEA with zero tillage and residue retention practices. Similarly, conservation agriculture-based residue management practices i.e., reduced tillage, zero tillage, and permanent bed planting with residue retention significantly (p<0.05) increased the biochemical properties and carbon (C) pools within aggregates and microbial diversity in earthworm casts and guts than the conventional tillage (CT). Whereas, phenol oxidase and peroxidase were in reverse trend. Large macroaggregates had higher dehydrogenase, fluorescein diacetate, cellulase, xylanase, β-glucosidase, total carbohydrate carbon, C pools, and total organic C than the macro and microaggregates. The microbial diversity within earthworm guts and the cast were significantly higher in conservation tillage practices as compared with CT. The wheat grain yield under DSRRT/ZTW+R was 10.6% higher as compared with PTR/CTW-R. However, in maize-wheat systems, treatments PBM+RN120/ ZTW+RN120 led to an increase in maize grain yield by 23.2%, wheat grain yield by 7.4%, and system grain productivity by 16.4% as compared to FBM-RN120/CTW-RN120. Wheat grain yield under DSRN120D/ZTW+RN120D was 5.57 t ha-1 and 5.37 t ha-1 was under PTRN120F/ CTW-RN120F. The principal component analysis elucidated xylanase and phenol oxidase in rice-wheat systems; total polysaccharides carbon and total carbohydrate carbon in maize-wheat systems were sensitive indicators of soil quality. In rice-wheat and maize-wheat systems, Lampito mauritii and Metaphire posthuman were the dominating earthworm species. The sequencing results identified the bacteria species as Stenotrophomonas rhizophila and the fungus species as Torula fici, Fusarium fujikuroi, and Fusarium niskaloi. Thus, our study suggests that conservation agriculture-based residue management practices can be beneficial to the overall improvement of biological pools, aggregation and microbial diversity in earthworm cast and guts.EnglishThesis