European Journal of Sustainable Agroecosystems

Background and Objective: Soil degradation on a global scale and a decrease in nutrient availability pose a risk to crop yield and food security. The use of green manure is an effective approach towards improved soil quality and nutrient cycling in the process of sustainable agriculture. The purpose of this work was to assess the impact of this agricultural practice on soil enzyme activity, microbial activity, nutrient availability, and crop productivity in different agricultural systems. 
Methods: A three-year field trial was performed in Northern India, under rice-wheat cropping system with alluvial soil grown under four distinct treatment conditions (Sesbania aculeata, Crotalaria juncea, Vigna unguiculata and control) at incorporation during the flowering stage. Soil samples were collected at post incorporation intervals of 0, 15, 30, 60 and 120 days for analysis of dehydrogenase, urease, phosphatase, β-glucosidase, arylsulfatase and catalase activities. 
Results: The use of green manure led to a substantial increase (p < 0.05) in the activity of soil enzymes. The highest recorded level of dehydrogenase was found in plants of Sesbania, with the readings reaching 3.84 μmol TPF g⁻¹ 24h⁻¹ at 30 days after the addition of organic substances to soil. In addition, soil organic carbon was observed to increase by 18-24% from control. Besides that, the rate of nitrogen mineralization experienced an increase of 32-41% in treatments with green manure. The yield of wheat extended by 15-22% after the introduction of green fertilizer. Moreover, microbial biomass carbon was found to increase by 28-35% in treatments with cultivated plants. Finally, correlation analysis showed strong positive relationships between enzyme activity and soil fertility (r = 0.78-0.89). 
Conclusion: The introduction of green manure has greatly benefited soil health indicators, nutrient cycling capacity, and crop yields. The species Sesbania aculeata has been singled out as the best species to boost soil enzyme activity and sustainability outcomes. The findings suggest integrating green manure into rice-wheat cropping systems to maintain soil fertility, decrease the input of external nutrients, and achieve more sustainable crop production.