玉米冠层氮素养分垂直分布遥感监测研究

The maize usually has an obvious vertical distribution characteristic of canopy nitrogen. When it under a nitrogen stress, the lower canopy leaves often firstly show the corresponding nutritional deficiency symptom. Therefore, an early diagnostic methods of the middle and lower maize canopy nitrogen status is urgently needed. The goal of this project is how to build a nitrogen version model basing on canopy nitrogen vertical distribution characteristics by hyperspectral remote sensing, and finally to realize the rapid and accurate monitoring nitrogen nutrition status of maize. There are three research contents, including: (1) to clarify the relations between the nitrogen vertical distribution characteristics and the light distribution characteristics in maize canopy, and build mathematical model of maize canopy nitrogen vertical distribution. (2) to study spectral response characteristics of maize canopy nitrogen vertical distribution and their relationships with the light distribution characteristics, and to determine the spectral contributions of different vertical layers to the entire canopies and canopy detectable depth. (3) to build the nitrogen version model basing on canopy nitrogen vertical distribution characteristics by hyperspectral remote sensing and test its effectiveness. The study results can offer the theoretical and technological basis for crop precise and variable rate nitrogen management.

玉米冠层氮素养分具有明显的垂向异质性，氮素缺乏时下部叶片首先表现出缺素症状，迫切需要玉米中下部叶片大面积早期快速监测方法。本项目拟通过田间小区试验和分层光谱探测，深入分析玉米冠层氮素养分垂直分布与冠层内光分布的关系，重点研究冠层氮素养分垂直分布的光谱响应机理以及从整体冠层光谱中提取分层光谱信息的方法，构建综合考虑冠层内光分布特征的玉米冠层氮素养分垂直分布光谱反演模型。具体研究内容包括：（1）阐明玉米冠层氮素养分垂直分布与光分布间的关系，建立定量描述冠层氮素养分垂直分布的农学模型；（2）探讨冠层氮素养分垂直分布的光谱响应机理及其与光分布间的关系，明确不同层次养分对整体冠层光谱响应的贡献及遥感可探测冠层深度；（3）将玉米冠层氮素垂直分布农学模型与遥感机理模型链接，构建玉米冠层氮素养分垂直分布光谱反演模型，并对其反演效果进行检验。为作物氮素精准管理、变量投入提供科学的理论方法和技术支撑。

实施作物氮素养分垂直分布监测可为作物早期养分胁迫诊断以及及时指导施肥管理提供技术支撑。本项目通过开展了野外玉米小区氮肥控制实验与农户地块综合实验，阐明了作物冠层结构（叶面积指数）和组分参数（叶绿素、氮素）的垂直分布特征与光分布特征，明确了不同株型对作物结构和组分参数垂直分布的影响；探讨分析了作物氮素、叶绿素、类胡萝卜素的遥感探测机理，提出了面向作物养分监测的色素比值监测方法，构建了用于类胡萝卜素监测的新的类胡萝卜素植被指数和用于色素比值监测的类胡萝卜素与叶绿素植被指数；提出了作物养分垂直分布多角度遥感监测方法，筛选出了多角度遥感监测冠层各层养分的最适观测角度和植被指数，建立了氮素养分垂直分布遥感监测模型，阐明了不同株型对作物养分垂直分布遥感探测的影响；设计研制了一种用于作物冠层垂直分布信息获取的便携式手动多角度观测装置，解决了现有技术中多角度观测装置的便携性差、操作灵活性低、地表破坏性大及成本高的问题。研究成果可为作物氮素精准管理、变量投入提供科学的理论方法和技术支撑。