Variations in Soil Organic C and N Storage Due to Cultivation Practices in the Gangetic Plain, India

摘要

The storage of soil organic C and total N were estimated in a marginal grassland, and two contrasting (dryland or rainfed and irrigated) rice based agroecosystems located in close proximity in the Gangetic plain. Total organic C and N mass in soil (0-30 cm depth) was significantly higher in the grassland (organic C, 55 Mg ha~(-1); total N, 5.8 Mg ha~(-1)) than in the irrigated (organic C, 26 Mg ha~(-1); total N, 2.8 Mg ha~(-1)) and dryland (organic C, 22 Mg ha~(-1); total N, 2.3 Mg ha~(-1)) agroecosystems. Within three decades organic matter status in the grassland almost doubled relative to both agroecosystems. Comparing the two types of agricultural practices, organic C storage was significantly lesser in the dryland than in irrigated agroecosystem, especially in > 10 cm depths. Storage of soil organic C and total N in different soil layers in the irrigated agroecosystem was 12-18% and 16-33%, respectively greater than the dryland agroecosystem. The dryland agroecosystem has attained distinctly lesser soil organic matter level compared to the irrigated agroecosystem despite of its higher root detritus level. It is suggested that management practices in dryland agroecosystem should aim towards longer residence of root detritus and soil moisture to increase soil C and N storage for enhanced crop productivity.