Prediction of Adsorbed Phosphorus and Erodibility Using Soil Magnetic Susceptibility On Different Geomorphic Surfaces of Sugarcane Growing Areas.

Traditional technologies to measure phosphorus adsorbed (Pads) and erodibility are relatively expensive and are also arousing the scientific society with the necessity of developing methodologies to assess the soil attributes within the landscape without using relatively expensive infrastructures. Iron and aluminum oxides of the clay fraction influence Pads and soil erodibility. These minerals own magnetic susceptibility (MS) in detectable levels. The magnetic characteristics may therefore be correlated with Pad and erodibility in low organic matter soils. In this sense, this study aims to evaluate the spatial variability of Pads and erodibility, and correlate these attributes with MS. Soil samples were collected at transect every 25 m (100 samples) and by its sides (100 samples) as well as an area of 500 ha (1 sample each six hectare). Geomorphic surfaces (GSs) were mapped within the entire field area. The soil samples were taken to the laboratory for chemical, physical and mineralogical analyses and the spatial distribution pattern of soil attributes was obtained by statistics and geostatistics. The GSs influenced the variability of Pads and erodibility. In GS III were found higher Pads values and lower of MS. The higher Pads values might be explained due to the iron oxides presence, which in higher contents, presents higher density of OH^- groups, thus presenting a greater affinity to phosphorus. The lower erodibility occurred on the GS III (with higher iron and gibbsite) presented the best physical condition (lower density, higher porosity and aggregates). MS obtained a positive correlation to the Pads and negative correlation to the erodibility. These results demonstrate that MS can be a strong candidate as a predictor of a pedotransfer function in predicting the studied attributes in order to map large areas.