Development of DRIS norms for evaluating nitrogen, phosphorus, potassium and sulphur requirements of rice crop

A crop nutrition survey was conducted in five development blocks covering 125 rice fields in district Ghazipur of U.P. for developing DRIS foliar diagnostic norms for N, P, K and S. The sample population was divided into low (<3.9 Mg ha⁻¹ with 63 observations) and high yield groups (>3.9 Mg ha¹ with 62 observations) for developing the DRIS foliar diagnostic norms. Leaf samples were obtained at tillering and booting stages and analyzed for N, P, K and S content. Crop yields were calculated by harvesting 100 m² of the cropped area in each field. The degree of nutrient imbalances in the rice plant expressed in terms of DRIS indices indicated the extent to which a particular nutrient deviated from the established norms. The advantage of DRIS system in predicting nutrient imbalances when the nutrient concentration in rice plant was below or above critical level range was observed. It was also noticed that these DRIS norms were different from those established elsewhere. The results indicate that local calibration of DRIS norms are required and the published DRIS norms developed in a different climatic location for a crop may not be universally applicable. Critical nutrient concentration (CNC) and DRIS norms were not found compatible. The DRIS approach appeared to be better than CNC for predicting nutrient requirements for higher yields.