Key variable for simulating critical nitrogen dilution curve of wheat: Leaf area ratio-driven approach

Abstract

Nitrogen (N) dilution curves, a pivotal tool for N nutrition diagnosis, have been developed using different winter wheat (Triticum aestivum L.) tissues. However, few studies have attempted to establish critical nitrogen (Nc) dilution curves based on the leaf area ratio (LAR) to improve the monitoring accuracy of N status. In this study, three field experiments using eight N treatments and four wheat varieties were conducted in Jiangsu Province of China from 2013 to 2016. The empirical relationship of LAR with shoot biomass (expressed as dry matter) was developed under different N conditions. The results showed that LAR was a reliable index, which reduced the effects of wheat varieties and years compared with the traditional indicators. The N nutrition index (NNI) based on the LAR approach (NNI-LAR) produced equivalent results to that based on shoot biomass. Moreover, the NNI-LAR better predicted accumulated N deficit and best estimated the relative yield compared with the other two indicator-based NNI models. Therefore, the LAR-based approach improved the prediction accuracy of Nc, accumulated N deficit, and relative yield, and it would be an optimal choice to conveniently diagnose the N status of winter wheat under field conditions.