Desenvolvimento de metodologia para determinação de textura de solo com sensores ópticos

Abstract

The measurement of the concentration and granulometry of suspended solids in liquid medium has importance in soil physics and agronomy for soil texture determination, which is an important characteristic in soil management, as it influences the degree of cohesion and adhesion between the constituent particles. The relative levels of clay, silt and sand contained in the soil and indicated in the texture influence the rate of infiltration and water retention, aeration and nutrient availability. In the last decades, the use of optical sensors as an indirect way of determining the Suspended Sediment Concentration (SSC) has been highlighted in the monitoring programs of sediment transport suspended in rivers. However, applications of the methodology in soil texture determination were not found in the literature. The present work aims to calibrate a simple optical system of diode and photodiode, in turbidimetric configuration, to obtain soil texture. The methodology is based on the application of Stokes's Law to a system containing a known concentration of the soil to be analyzed in suspension in a tube. The results show that the average clay absorbance and the average silt absorbance obtained with the optical device had a correlation with the soil textures determined by the traditional method applied in soil laboratories, which consists of sieving and measuring the density of the clay content suspended.