Assessment of climatic variability on optimal N in long-termrice cropping system

Abstract

Climatic variability is one of the most significant factors influencing year-to-year cropproduction, even in high yielding and high-technology agricultural areas. Many studies haveattributed variation in yield and crop response to N fertilizer in general terms to differencesin varietal characteristics, but few attempts have been made to systematically disentangle thecontributions of the genotype from other factors as climatic conditions. In this study, we usedORYZA V3 rice crop model to evaluate impact of climatic variability on optimum nitrogenapplication rate in rice cropping system. The results show that, solar radiation and Nmanagement practices play important roles in the response of N in grain yield. Maximum andminimum temperature has less effect on the grain yield compared to the solar radiation.Optimum N was higher in the dry season compared with the early wet season. Optimum Nrate for the grain yield was around 200, 150 and 100. Nutrient use efficiency (NUE) washigher in early wet season (EWS) and late set season (LWS) in higher rate of nitrogencompared to the dry season (DS). Observed grain yield and simulated grain yield was almostsimilar in both seasons. The ORYZA simulation model performs well for estimating optimumN application.