Evaluation of soil fertility with spectrophotometer and spectroradiometer

摘要

An evaluation method of soil fertility was developed based on spectroscopy. A handheld spectroradiometer and a desktop spectrophotometer were used for measuring spectral reflectance of soil in a field and in a laboratory respectively. The spectroradiometer has a 325-1075nm measurable range in 1nm resolution, while the spectrophotometer has a 4000 -12000 cm~(-1) measurable range in 0.04cm~(-1) resolution. A 50x300 m~2 small farm was selected as test field. The farm was divided into 150 grids with grid size of 10x10 m~2. Firstly the spectroradiometer was used to measure spectral reflectance of soil surface in all grids, and then a soil sample (about 1000 g) was collected from each grid and put into a sealed container. In laboratory, the spectrophotometer was used to measure spectral reflectance of soil samples at the earliest possible time. Finally some important soil fertility parameters, moisture, nitrogen content, and organic matter content, were analyzed. Correlation and regression analyses for estimating these soil parameters were conducted. Result shows that most soil parameters can be evaluated by NIR spectral reflectance obtained by both the spectrophotometer and the spectroradiometer. For soil moisture, a linear regression model was available in high accuracy. We demonstrated that the feasibility to estimate nitrogen content, and organic matter content by spectral reflectance.