春玉米磷素营养的光谱响应及诊断

通过盆栽试验监测不同磷营养水平春玉米典型生育期叶片光谱变化,并对叶片光谱反射率与叶片磷含量做了相关分析。结果表明,春玉米大喇叭口期是磷素营养的光谱响应敏感期,3507～30.nm和14201～800.nm是磷素营养的光谱敏感波段。该生育期构建的单波段高光谱变量、窄波段光谱变量和宽波段光谱变量与叶片磷含量都存在显著或极显著的回归关系;窄波段光谱变量比值指数R6725/6256和R61745/15856与叶片磷含量的回归关系达到了极显著水平,R625/555达到显著水平。可见光波段光谱变量与磷含量的回归关系优于近红外波段光谱变量与磷含量的回归关系,表明可见光波段叶片光谱反射率可能更适合春玉米磷营养状况的评价。不同波段宽度的光谱变量分析表明,在敏感波段范围内,801～00.nm波段平均的叶片宽波段光谱反射率没有降低对叶片磷含量的估算精度。

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 R725/625 and R1745/1585 reached most significant level,then R625/555 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.