Soil Organic and Enzymatic Properties as Influenced by Green Manuring and Establishment Methods in Rice-rice system

The field study was conducted during kharif and rabi seasons of 2016-17, 2017-18 and 2018-19 at Instructional Farm of College of Agriculture, Odisha University of Agriculture and Technology, Bhubaneswar to evaluate the effect of green manuring and establishment methods on growth parameters of rice-rice system. The experimental site was sandy loam in texture, slightly acidic in reaction, low in available nitrogen (198 kg/ha), medium in available phosphorus (18 kg/ha), potassium (193 kg/ha), OC (0.51%) with EC (0.20 dS/m). The rice varieties “Swarna sub-I” and “Lalat” were grown in kharif and rabi seasons, respectively. The experiment was designed with two groups of treatments, one without green manuring and the other with green manuring with Sesbania aculeata in main plot along with sequence of three establishment methods namely, Puddled Transplanted Rice (PTR), Non Puddled Transplanted Rice (NPTR) and Direct Seeded Rice (DSR) making it a total of nine establishment methods i.e PTR-PTR, PTR-NPTR, PTR-DSR, NPTR-PTR, NPTR-NPTR, NPTR-DSR, DSR-PTR, DSR-NPTR, DSR-DSR as sub plots in kharif and rabi seasons. From the above experiment, it is observed that the soil organic carbon in green manured plots were superior with respect to soil biological properties as it realized higher soil organic carbon (0.51%), microbial biomass carbon (246.29 μg C/g soil), microbial biomass nitrogen (83.5 μg N/g soil). The enzymatic activities of the soil were also enhanced with green manuring recording higher dehydrogenase and phosphatase activity of 226.40 mg TPF/g soil/24 hrs and 352.81 mg p-nitrophenol/kg soil/1hr respectively, at 0-15 cm after 3 years of rice-rice system. Among the establishment methods, DSR-DSR method of establishment recorded higher soil organic carbon, microbial biomass carbon and microbial biomass nitrogen of 0.58%, 251.33 μg C/g soil and 89.36 μg N/g soil respectively. Similarly, the dehydrogenase and alkaline phosphatase activities were also enhanced under DSR-DSR method of establishment recording 242.60 mg TPF/g soil/24 hrs and 381.90 mg p-nitrophenol/kg soil/1hr respectively, after 3 years of rice-rice system.