Prediction of optimal nitrogren application rate of rice based on soil test values

This study evaluated the quadratic response plateau (QRP) and quadratic models for 3-5 years. two crop sequence data set with 4, 3 and 5 nitrogen fertilizer application rates in southern, western and eastern India. The quadratic response model predicted a maximum grain yield of 2-13% larger and an optimal N fertilizer rate 2-73% larger than predicted by the quadratic response plateau Model. These analyses indicate that the quadratic response plateau model is preferable to the quadratic model for predicting N fertilizer requirements of rice. Economic analyses also indicate that the benefits of using quadratic response plateau can be more than by using quadratic model. Site or season specific knowledge of crop nutrient requirements and nutrient supply front soil will be required in order to achieve maximum yields. (c) 2006 Elsevier B.V. All rights reserved.