Hyperspectral diagnosis of leaf N concentration of maize and variety difference

The accurate, rapid and timely monitoring and diagnosis of maize nitrogen (N) nutrition is the base of the reasonable application of N fertilizer. By using the method of potted plant experiment to precisely control the supply of N, the sensitive spectral band and diagnosis model of three kinds of maize (hybrid) for leaf N concentration (LNC) monitoring and their variety difference were studied. The results show that: 1) There is variety difference in correlation between the LNC and the leaf spectrum reflectance within the range of 350-2 500 nm, but it presents significant negative correlation at F=0.01 between 500-649 nm and 691-730 nm for all the three varieties (hybrid), and gets the highest correlation coefficient at the same wavelength. All of those show that an unified spectral band can be used to diagnose LNC in different varieties. 2) The quantitative equations of different varieties are established between maize LNC and normalized difference spectral index (NDSI) or ratio spectral index (RSI). The fitting degree is the best based on NDSI (714, 554) and RSI (714, 554) and is significantly at F=0.01 for the linear and exponential equations, so the derived regression models can be reliably used for estimating LNC in maize. 3) The deviation of estimation for maize LNC is the lowest when using the regression model derived from the same variety, but the deviation increases when using a model derived from multi-varieties or other variety. The maximum deviation of up or down estimation are 35.6% and 32.7%, respectively. The variety difference should be taken account, when using hyperspectral technique to diagnose the maize plant N status in researches and applications.