土样盒土表特征对近红外光谱测量土壤水分精度的影响

为了现场快速准确地检测土壤水肥状况，实现精细农业的目标。利用近红外光谱反射法测量土壤水分，了解土壤表面特征对测试结果的影响规律，是能否有效提高测量精度的关键，对快速测量大田的养分含量，实现精确定量管理也有重要的现实意义。该研究用近红外光谱技术测量了6个不同土样的土壤含水率，经回归分析发现：与直尺刮平相比，盒土表面筛控刮平处理的土样，其土壤含水率与光谱的相对吸收率之间有更好的相关性；不同类型的土样对光谱的相对吸收率是：中壤土＞重壤土＞轻壤土；在相同的表面处理条件下，粒径0.5≤d≤1 mm的土样，其含水率与光谱相对吸收率之间的相关性均较高。研究表明，土样表面均匀连续是测量精度提高的主要原因；而裂纹和划痕是影响测量精度的重要因素。

Influence of soil surface disposal on precision of measuring soil water by near-infrared spectroscopy

In order to measure fertilizing indexes of soil quickly, precisely and in the field for precision farming, it is a key to improve the accuracy of soil water measurement by finding out the pattern influencing rules of soil surface on the measurement by the near-infrared reflectance spectroscopy, and is also helpful to measure soil nutrients by the reflectance technique. Six soil sample with different water level of soil samples were measured by near-infrared reflectance spectroscopy. By regression analysis, it was found that the correlation between the soil water content and the relative spectral absorptivity by using of a meshwork controlled surface finishing was better than by only ruler finishing. Among the different type of soils, the order of relative absorptivity from high to low is as following, medium loam, heavy loam and light loam. For different partied size of soil with the same surface disposal method, the correlation is the highest for the soil whose particle sizes are within the range of 0.5 to 1 mm. The results showed that the uniformly continuous soil surface was the dominant cause for the improved result and the surface flaw and scratches were the main factors to degrade the measurement accuracy.