氮素供需协同的玉米营养光谱诊断机制与推荐施肥

Corn leaves and root soil samples spectrum will be systematically and scientifically observed in the whole growing stage under different nitrogen levels by means of field experiment and potted experiment. Firstly, correlativity between leaf N content and soil organic matter, ammonium nitrogen, nitrate nitrogen will be analyzed from spatial and temporal aspects in order to get to bottom of its variation. And correlativity between different layers leaf spectrum and soil organic matter, ammonium nitrogen, nitrate nitrogen will be analyzed. Secondly, close-around root soils spectrum will be researched. Furthermore, soils characteristic parameters including of wave location, depth, width, slope, absorption apex symmetry, area will be analyzed and acquired. Accordingly, soils spectrum database will be built up based on nitrogen nutrition. Finally, proper spectrum characteristic parameters will be designed and brought up in order to construct spectrum diagnosis model for soil nutrients based on soils spectrum and leaves spectrum. So, its goal will be achieved that clear spectrum diagnosis mechanism of soil nutrients. Research results not only will offer trial data and theoretical evidence for plant spectrum response mechanism, for corn and others nitrogen nutrition spectrum diagnosis, but also will be greatly significant in practice for right supplying nitrogen fertilizer and improving its use efficiency.

本项目从田间试验和盆栽试验入手，利用高光谱技术对不同氮处理下玉米整个生育期叶片和根部土壤样品进行光谱监测，通过（1）从空间角度和时间角度分析叶片氮素含量与根区土壤有机质、铵态氮和硝态氮含量变化的相关关系；探明二者在空间尺度和时间尺度的变化规律；（2）研究根区土壤的光谱特征，提取光谱特征参数，建立根区土壤光谱数据库；筛选和构建适宜的光谱特征参量，建立土壤养分光谱诊断模型；（3）分析不同层位叶片光谱与根部土壤有机质、铵态氮和硝态氮的相关关系，筛选和构建适宜的光谱特征参量，建立基于叶片光谱的土壤养分诊断模型；（4）实现作物营养光谱诊断和土壤养分光谱诊断的衔接与耦合，建立土壤作物氮素协同的玉米营养光谱诊断模型与推荐施肥模型。结合前期青年自然基金结果，可为为玉米乃至其他作物氮素营养和土壤养分状况的光谱诊断提供新的认识和实验证据，对于指导作物合理追施氮肥，提高氮肥利用率具有重大实践意义。

为使土壤养分供应与作物养分需求二者间协同作用能够在光谱技术支撑下衔接与耦合，为使光谱技术能在植物营养诊断与施肥领域发挥最大作用，在利用光谱技术进行作物营养诊断的同时，能够实时了解土壤养分状况，建立养分供需协同的作物营养光谱诊断机制与方法，本项目从不同氮营养水平下的玉米叶片光谱获取入手，从空间角度和时间角度分析叶片氮含量与根区土壤无机氮含量变化的相关关系；明确了不同生育期利用叶片光谱进行氮素营养诊断的叶片层位；分析了不同层位叶片光谱与植株氮含量、根区土壤无机氮含量的相关关系；针对玉米拔节期下层叶片、大喇叭口期上层叶片、开花吐丝期穗位叶、灌浆期上层叶片进行诊断的比值光谱指数分别是RSI(1811, 1842)、RSI(720, 557)、RSI(688, 644)、RSI(600, 511)。针对根区土壤无机氮含量进行诊断的光谱参数分别是RVI-2、RVI-2、RSI(567,519)和RSI(802,816)。最小偏二乘法（PLSR）建立的诊断模型能对拔节期、大喇叭口期、开花吐丝期很好的预测根区土壤无机氮含量。本项目实现作物营养光谱诊断和土壤养分光谱诊断的衔接与耦合，建立土壤作物氮素协同的玉米营养光谱诊断模型，可为玉米乃至其他作物氮素营养和土壤养分状况的光谱诊断提供新的认识和实验证据，对于指导作物合理追施氮肥，提高氮肥利用率具有重大实践意义。