Singh, Santosh KumarKUMAR, VIKASH2023-02-012023-02-012022M /SS/090/2020-21https://krishikosh.egranth.ac.in/handle/1/5810193022The research was carried out as part of an ongoing field experiment under the AICRP on Micro Secondary and Pollutant Elements in Soil and Plants, which began in Kharif 1985 in light-textured calcareous soil. The experiment was in randomized block design with four fertility levels 0, 50%, 100%, and 150% of the recommended dose of fertilizer (RDF) for each crop), and six replications with two cropping systems viz. Rice-Mustard-Moong (R-M-M) and Rice-Wheat-Sorghum (RW- S). The RDF for wheat and rice were 120:60:40; for moong-20:50:30; for Sorghum-60:50:30; and for mustard-60:40:30. After ten cropping cycles, because of substantial micronutrient deficiencies, particularly zinc, in plots receiving 150% of the RDF, out of six replications, 4 replication were superimposed with (10 kg/ha Zinc, 10 kg/ha Zinc + 5 t/ha FYM, 10 t/ha FYM and 10 kg/ha Zinc + 10 t/ha FYM). The superimposed treatments were applied in alternate years. No replication was left for statistical analysis in RBD due to superimposition in four replications. To compare the superimposed treatments, a paired t-test was used. After the 109th rice crop was harvested in 2021, during the 37th crop cycle, the current research was conducted. From the current study, Among superimposed treatment the conjoint application of 10 kg Zn along with 10 t FYM/ha proved the best treatment with respect to soil organic carbon dynamics in both the cropping system. The combined application of 10 kg Zn along with 10 t FYM/ha, it was observed that there were significant changes in soil organic carbon, fractions of soil organic carbon, total organic carbon, soil organic carbon stock, lability index and soil microbial biomass carbon while in subsurface soil no significant effect of different superimposed treatments on soil organic carbon dynamics. The values of different fractions of soil organic carbon such as very labile carbon, labile carbon, non labile carbon and less labile carbon content in treatment receiving with 10kg Zn/ha with 10t FYM superimposed treatment over control was found to be 0.41%, 0.19%, 0.12% and 0.67% in R-W-S crop rotation while in R-MM rotation it was found to be 0.44%, 0.23%, 0.08%, 0.58%. Among different fractions of soil organic carbon, the content of very labile and labile carbon fractions were found more in R-M-M rotation than in R-W-S rotation for each superimposed treatment. However, less labile and non-labile organic carbon fractions were higher in R-W-S rotation. A similar trend was also observed for total organic carbon, soil organic carbon stock and soil microbial biomass carbon. Soil organic carbon, total organic carbon, and microbial biomass carbon the percent increased in superimposed treatment over control was found to be 26.3%, 39% and 32.9% in R-W-S crop rotation while in R-M-M was found to be 30.7%, 38.4%, and 24.5%. Rice grain yield was positively and highly significantly correlated with the soil's very labile carbon, labile carbon, and organic carbon in R-W-S cropping system and in R-M-M cropping system rice yield was was positively and highly significant with very labile carbon, labile carbon, organic carbon and microbial biomass carbon. It was also positively and significantly correlated with less labile, total organic carbon content in both the cropping system. However, the non-labile carbon fraction didn‘t significantly improve rice grain yield in both the cropping system.EnglishThesis