Impact of Integrated Application of Biogas Slurry and Chemical Fertilizer on Soil Microbial Biomass Carbon and Enzymes Activity under Rice-Wheat Cropping System

Field experiment was executed under irrigated conditions during 2022-2024 to study the impact of integrated application of biogas slurry and organo-mineral amendments on soil microbial biomass carbon (MBC) and enzyme activity under rice-wheat cropping system (RWCS). In this experiment, the doses of urea and biogas slurry (BGS) were applied for both rice and wheat crop with 6 different treatments and 4 replications viz., T0-Control (where no urea/BGS applied), T1-100% N by recommended dose of fertilizer (urea), T2 – 25% N by BGS + 75% N by recommended dose of fertilizer, T3-50% N by BGS + 50% N by recommended dose of fertilizer, T4-75% N by BGS + 25% N by recommended dose of fertilizer and T5-100% N by BGS. The soil MBC increased in all the treatments from the initial year (2023) to next year (2024) from 0.98 to 9.0 per cent. The MBC of T5 treatment was significantly higher than other treatments, viz., T0, T1, T2 and T3 but it was at par with T4 treatment in both years. In all the treatments, the dehydrogenase activity was increased from the initial year (2023) to next year (2024), which was account 8.48 per cent in T5 treatment, followed by T2/T3 (8%), T4 (7.27%), T1 (1.45%) and T0 (1.37%), respectively. The activity of the acid and alkaline phosphatase was observed to be significantly higher in the T5 treatment at the reproductive stage of wheat, while minimum activity was recorded in the control (T0) during both years. The maximum á- glucosidase activity was 404.2 mg mL-1 (2023) and 415.5 mg mL-1 (2024) in T5 treatment with a 100% dose of biogas slurry application, and it was significantly higher than T0, T1, T2, T3 and T4 treatment. Overall, the higher activity of â-glucosidase was recorded in 2024 as compared to 2023. The maximum â-glucosidase activity was recorded in T5 treatment in 2023 (226.0 μg pNP g-1 dry soil h-1) and 2024 (232.4 μg pNP g-1 dry soil h-1). While minimum â-glucosidase activity was recorded in T0 treatment in the year 2023 (169.3 μg pNP g-1 dry soil h-1) and 2024 (172.4 μg pNP g-1 dry soil h-1) In case of N-acetyl glycosaminidase (NAG), the activity was recorded maximum in T4 (4.65%) and T3 (3.27%) treatments in comparison to T5 (3.25%) treatment. However, the minimum NAG activity was observed in T0 (0.43%) and T1 (0.67%) treatment, respectively. Hence, this experiment demonstrated that the MBC and most of the enzyme activities were maximum when higher doses of biogas slurry were applied. The study concludes that biogas slurry has a significant positive impact on soil enzymes, which are crucial for maintaining soil health and biological diversity.