Critical Nitrogen Dilution Curve for Winter Wheat Based On the Leaf Area Index During the Vegetative Period in East China.

Abstract Accurately forecasting the nitrogen (N) required for plant growth can aid in optimizing grain yield, farm profit, and N use efficiency. The objectives of present study were to establish the critical N concentration (Nc) dilution curve for winter wheat based on the leaf area index (LAI), to compare this curve with Nc dilution curves for winter wheat on dry matter (DM) basis and to assess the plausibility to estimate the level N nutrition for winter wheat in east China. Four field experiments were conducted with varied N rates in east China, which were established and validated this Nc curve. Twenty plants from each plot were sampled from the spring regrowth to heading stages for growth analysis. Relationships between the critical N concentration and the LAI could be described by negative power equations Nc=4.06LAI -0.4, when LAI ranged from 1.4 to 7.5. However, for LAI <1.4, the constant critical value Nc = 3.58 % was applied, which was independent of LAI. The N nutrition index (NNI) ranged from 0.34 to 1.31 during the vegetative stage from 2009 to 2011 seasons. There was a significantly positive relationship between the difference value of NNI and the difference value of N application rate across four growth stages, and testing of the models with independent data gave to a root mean-squared error of 18.99 kg ha-1. These results demonstrated that the Nc dilution curve based on LAI can be a useful tool for crop modeling, N status diagnosis, and N fertilizer application decisions.