基于光谱技术的水稻叶片氮素测定仪的开发

Development of fast-determination instrument for rice leaf nitrogen content based on spectroscopy

在理论分析的基础上设计开发了一套基于光谱技术的水稻叶片SPAD值和氮素测定仪。该测定仪主要包括光路部分、调理电路和控制与数据采集器等。光路部分包括光源、检测点以及光电传感器等元器件,主要作用是:控制光源的亮灭、收集透过叶片光线、将光信号转换为电信号;调理电路主要将所得微弱电信号进行电流电压转换以及放大到合适的幅度;控制与数据采集器包括AD转换电路,液晶显示电路和SD卡存储电路。对该测定仪的性能进行了测试,试验分为两步:先建立AD采样电压信号与SPAD值之间的模型,然后建立SPAD值与氮素之间的模型。经过大量的试验测得:传感器转换的电压信号与SPAD值之间存在很高的相关性(R2=0.956),SPAD值与氮含量建立的模型的决定系数为R2=0.802,结合以上两种模型得到该仪器的氮素模型的决定系数为R2=0.766。该仪器适合用于田间水稻叶片氮素含量的快速测量。

An instrument used to measure the SPAD values and nitrogen content for rice leaf was developed based on the spectral technique.The instrument consists of optical unit,conditioning unit and control and data acquisition unit.The optical unit includes light source,detection point and photoelectric sensor.Its primary role is to control the light on or off,collect the light permeating through the leaves,and convert the optical signal to electrical signal.Conditioning unit mainly converts the weak signal to current or voltage,and enlarges it to suitable range.Control and data acquisition unit includes the AD conversion circuit,liquid crystal display circuit and SD card storage circuit.In this study,the performance of the instrument was tested through two steps：1） Set up the prediction model between AD sampling voltage value and the SPAD value;2） Set up the prediction model between SPAD value and the nitrogen content.After several tests,the voltage value had a high correlation with the SPAD value,and the decision coefficient（R2） was 0.956.The decision coefficient（R2） between SPAD value and nitrogen content reached 0.802.Combining the results of two models,the decision coefficient（R2） was 0.766 for nitrogen content prediction.It show that the instrument can successfully used to quick measurement for rice leaf nitrogen content in field.