基于光谱技术的土壤有机质快速测定仪的开发

在理论分析的基础上设计开发了一套基于光谱技术的土壤有机质测定仪.测定仪由光学部分和电路部分组成.光学部分包括光源、传导光纤、检测室、样品盒、滤光片以及光电传感器等元器件,主要作用是:把光源的光导入土样表面、收集土壤表面的反射光、滤光、将光信号转换为电信号;电路部分包括放大电路,AD转换电路,液晶显示电路和U盘存储电路.选取三种滤光片对仪器进行了标定实验,三种滤光片的中心波长分别是530,765和850 nm,被测土样有烘干土样和风干土样.试验结果表明:当滤光片中心波长为850 nm时烘干土样获得最高测量精度(r2=0.930),在此条件下风干土样预测模型的决定系数为r2=0.711,虽然受水分的影响精度有所降低,但仍可满足田间快速测试的要求.

Development of Soil-Organic-Matter Fast-Determination Instrument Based on Spectroscopy

An instrument used to measure the content of soil organic matter was developed based on spectroscopy.The instrument consists of an optical unit and an electronic unit.The optical unit is used to collect the reflecting light from soil surface and change the filtered light into the electrical signal.The electronic unit includes an amplifying circuit,an A/D circuit,and a display and storage circuit.Three wavebands of filters,530,765,and 850 nm,were selected in the performance test in order to determine the optimal one.The soil samples tested include two types,dried soil and air-dry soil.The result shows that there is highest correlation between the reflectance and the content of soil organic matter at the wavelength of 850 nm(r2=0.930)for dried soil.While the coefficient of determination r2 is abouu 0.711 for air-dry soil at the same wavelength.Although the actual precision is lower because of the soil moisture,it is practical in real-time measurement in the field.