Residual Management of Sunnhemp (Crotalaria juncea) Varieties in Releasing Soil Nutrients and Their Impact on Succeeding Rice Crop

Background: Legume is an essential alternative approach in the organic agricultural system to produce ecologically safe nitrogen (N), while restoring soil health in an appropriate mode to supply nutrients for subsequent crops. The experimental study was conducted in the summer (March) 2024 at Tamil Nadu rice research institute, Aduthurai, Tamil Nadu to study the residual effect of Sunnhemp varieties either alone or incorporation along with rice stubbles and their impact on nutrient availability of soil, soil organic carbon and yield attributes of succeeding rice in sunnhemp-rice cropping system. Methods: The field trial was set up in a split-plot design with fivefold replication during the summer of 2024, with the main plot consisting of two Sunnhemp varieties (V1 - ADT 1, V2 - CO 1) and the subplot comprising of Rice residues (W1 - Without residues, W2 - With residues). The treated Sunnhemp varieties were ADT 1 and CO 1; the succeeding rice variety was ADT 57. Result: The results indicated that there was a significant difference between the two varieties in terms of nutrient release pattern. The residual effect of Sunnhemp variety (ADT 1) with residues (V1W2) contributed sustained release of nitrogen (143.4 kg/ha), phosphorus (22.9 kg/ha) and potassium (56.4 kg/ha). The increase in soil organic carbon from the initial level was also 0.036% throughout the crop growth, which has greatly influenced the growth and yield attributes and eventually resulted in the highest grain and straw yield of the succeeding rice crop.