Spectral response and diagnosis of phosphorus nutrition in corn

Corn(Zea Mays L.) leaf spectrum was monitored at typical development stages with different rates of P supply by means of potted plant experiment.Correlation analysis was made between leaf spectral reflectance and leaf P content. The results showed that booting stage was the sensitive stage of spectral response and both 350-730 nm and 1420-1800 nm were the sensitive bands for P nutrition. Single band hyperspectral variables,narrow band spectral variables,broad band spectral variables and ratio vegetation index(RVI) were constructed at booting stage.And linear regression analysis was performed between those variables and leaf P content.The results of regression analysis showed that significant or most significant regression relationships existed between single band hyperspectral variables,narrow band spectral variables,broad band spectral variables and leaf P content.Regression relationship between leaf P content with R6725/6256 and R61745/15856 reached most significant level,then R6625/5556 was significant level. Moreover,regression relationships were better for visible band than near-infrared band.It was convinced that leaf reflectance in visible band was suitable for evaluating P nutrition condition compared with near-infrared band.By analyzing spectral variables of different band width,it was obvious that leaf spectral reflectance of 80-100 nm width did not decrease the precision of P content estimation compared with narrower width in the region of sensitive bands.