Estimation of Soil Loss Ratio for Rapeseed Crop (Brassica napus) from the USLE/RUSLE Model in Uruguay

Abstract

In Uruguay, since 1981 there is a legal framework by which it is declared of national interest to promote and regulate the use and conservation of soils and surface waters destinated to agricultural purposes. In this framework, the «Land Use and Management Plans» (PUMS) have been implemented as a technical norm that regulates land use. In compliance with this regulation, the loss of soil due to erosion of certain use and management is estimated with the EROSION 6.0 program, based on the USLE/RUSLE, in which each crop has its Soil Loss Ratio factor (RPS). For the production conditions of Uruguay, the rapeseed crop (Brassica napus L.) does not have the aforementioned factor. The objective of this work was to determine the RPS of rapeseed, for each crop period (CP). For four years data was collected from commercial farms and experimental sites located on the western coast of Uruguay. The average RPS values   obtained for PC1, PC2, PC3 and PC4 were 0.142, 0.079, 0.032 and 0.040, respectively. The variability of the RPS values   in PC1 and PC4, was explained by the soil cover by residues (CR) only (RPS_PC1 = 0.6772^e-0.028CR and RPS_PC4 = 0.4221 - 0.0091CR + 0.00005CR², respectively), while in PC2 and PC3 it was explained by the CR more air coverage (CobA) of the crop itself (RPS_PC2 = 0.38 - 0.0049CR + 0.000019CR² - 0.000018CobA² and RPS_PC3 = 0.225 - 0, 00237CR - 0.00084CobA + 0.00001CR², respectively).