Nutrient status and establishment of critical values and adequate ranges for different nutrients for rice (Oryza sativa L.) through Dris in Karimnagar district of Andhra Pradesh

The Diagnosis and Recommendation Integrated System (DRIS) foliar diagnostic norms were developed for N, P, K, S, Zn and Fe and identified the yield limiting nutrients in rice, based on crop nutrient survey of 150 rice fields in Karimnagar district of Andhra Pradesh in India. A wide variation in soils and management practices were noticed in selected rice fields under study. Index leaf samples were collected from all the selected fields at tillering stage and analyzed for N, P, K, S, Zn and Fe contents. A wide range of variation in chemical composition in index leaves was observed irrespective of yield level of no uniform trend. Based on critical nutrient concentration (CNC), N, S, Zn and Fe contents in index leaf samples of rice under study were deficient to an extent of 40, 44, 53 and 10% respectively, and no deficiencies were observed with respect to P and K. The extent of nutrient deficiencies diagnosed by CNC method was changed depending up on the critical level adopted. The direct correlation between N, P, K, S, Zn and Fe contents in index leaves and rice yields were poor. Based on the highest variance ratio between low and high yielding populations, forms of expression for different nutrients and their norms were selected. DRIS norms were established for various nutrient ratios obtained from high yielding population of rice crop and were further used to compute the DRIS indices, which assessed the yield limiting nutrients and their requirement in order of priority. The DRIS derived sufficiency ranges for N, P, K and S from nutrient survey of rice crop were 2.2 to 3.6, 0.30 to  0.38, 2.02 to 2.89 and 0.18 to 0.34% respectively. The sufficiency ranges for Zn and Fe were 14.9 to 26.3 and 19.7 to 167.8 mg kg-1 respectively. The lower critical values for the nutrients N, P, K, S, Zn and Fe for rice crop were established as 0.2, 0.3, 2.02, 0.18% and 14.93, 91.69 mg kg-1 respectively.