Effects of farming works on soil surface bidirectional reflectance measurements and modelling

A model describing the directional reflectance in the optical domain from cultivated soil surfaces, taking into account their farming direction, is presented in the paper. It is discussed on the background of the directional reflectance measurements of soil surfaces, being effects of farming works preparing the soil for colza sowing. The model considers a soil surface as equal-sized opaque spheroids of definite shape and size dispersed in a net of squares on a freely sloping plane. They are absorbed into the plane having with their tops at a height above it. Different values for this height, along and across the soil cultivation direction, are parameters which express the variation of soil surface irregularities caused by furrowed farming treatments. The structure is illuminated by direct solar and diffuse light. Wave energy is reflected from it taking into account the diffuse and the specular components. A set of geometrical parameters of the structure, the equivalent of the real rough soil surface, makes it possible to predict the soil directional reflectance in any illumination and viewing conditions. It was applied to trace the influence of the direction of furrows, caused by a seeder, on the soil bidirectional reflectance.