基于冠层光辐射异质性的小麦氮素诊断机理研究

本研究针对当前作物氮素遥感监测精度受冠层空间性的影响和限制这一亟待解决的实际问题，综合利用多角度反射探测冠层深度的优势，透射光谱穿透植被冠层的特点，探讨田间小麦冠层光辐射异质性及氮素诊断的感知机理。依托不同株型、种植密度和氮肥水平组合的小麦田间试验，采用多角度反射光谱、网格化冠层光分布和分层氮梯度测试方法，将定量分析光谱学、植物营养学与小麦栽培生理学知识相结合，研究株型、密度和氮肥等栽培因子对植株氮素组分、多角度反射光谱和冠层透射能谱的影响，解析反射光谱的方向性、冠层光衰减的空间性、氮素垂直分布的梯度性规律及三者间耦联机制，提取适宜表征小麦氮素组分及丰缺状况的专属能谱参数及其生物物理学关系，构建基于反射光方向性和透射光空间性相融合的小麦植株氮素诊断模型及感知技术。研究结果不仅丰富作物生长无损监测理论，而且拓宽氮素遥感监测和早期诊断方法与技术，提高作物氮肥精确管理水平，实现肥料减施增效环保。

The nondestructive sensing of wheat nitrogen status is critical for recommending top-dressing N amount, so as to achieve higher yield and high-efficiency utilization of agricultural resource efficiency. In view of the practical problems of lower precision in monitoring N affected by canopy spatial distribution, this research intends to explore the field wheat anisotropy and sensing mechanism of plant nitrogen diagnosis by comprehensive utilization of three-dimensional permeability of multi-angle reflection spectrum and transmission spectrum through the vegetation canopy. The field experiments were conducted with different plant type, planting density and nitrogen fertilizer level, and time-course measurements were taken on canopy spectral reflectance, plant light distribution, nitrogen vertical gradient by layered or directed testing method. The study investigated temporal and spatial dynamic characteristics of nitrogen components, canopy multi-angle reflectance spectra and canopy transmission spectral energy with fusion of spectral analysis, crops cultivation and plant nutrition under different cultivation measures. The project explain covariant relationship of multi-angle reflectance, transmission spectral energy and plant N vertical distribution, further extract suitable spectral parameters to indicate plant nitrogen composition and its abundance level. Plant nitrogen diagnosis models are established based on new fusion technique of the reflected light direction and transmitted light spatial variability. The indirect approach of early distinguishing wheat N deficiency with multi-source remote sensing were developed, which provided the theory basis and the key technology for monitoring and precisely evaluating wheat growth characteristics. The results of this project not only can enrich crop nondestructive monitoring theory, and broaden early N diagnosis method, which improve the level and efficiency of crop N management to promote fertilizer efficiency, yield loss inhibition and environmental protection.