REFLECTANCE OF LIGHT FROM THE SOIL SURFACE IN RELATION TO TILLAGE PRACTICES, CROP RESIDUES AND THE GROWTH OF CORN

Soil reflectance is of importance when estimating the radiation component of heat balance on the soil surface, and thus it affects various thermal reactions within the soil. A semi-empirical model was developed to estimate the surface reflectance of an agricultural field. The study was carried out for six soil tillage treatments, and a radiometer was used in the field to obtain the reflectance from each treatment. The model for the early crop growing stages, from emergence to almost complete crop cover, was based on the variations of the surface reflectance with soil surface moisture content, percent of residue cover and crop cover, with a correction term for soil surface roughness. When the crop covers almost all the soil surface. the reflectance depends only on the crop reflectance. The tests throughout the growing season showed that the model can be used successfully to predict sur-face reflectance under various soil and crop managements schemes.