Modelling of soil penetration resistance for an oxisol under no-tillage

soil penetration resistance is an important property that affects root growth and elongation and water movement in the soil. since no-till systems tend to increase organic matter in the soil, the purpose of this study was to evaluate the efficiency with which soil penetration resistance is estimated using a proposed model based on moisture content, density and organic matter content in an oxisol containing 665, 221 and 114 g kg-1 of clay, silt and sand respectively under annual no-till cropping, located in londrina, paraná state, brazil. penetration resistance was evaluated at random locations continually from may 2008 to february 2011, using an impact penetrometer to obtain a total of 960 replications. for the measurements, soil was sampled at depths of 0 to 20 cm to determine gravimetric moisture (g), bulk density (d) and organic matter content (m). the penetration resistance curve (pr) was adjusted using two non-linear models (pr = a db gc and pr' = a db gc md), where a, b, c and d are coefficients of the adjusted model. it was found that the model that included m was the most efficient for estimating pr, explaining 91 % of pr variability, compared to 82 % of the other model.