SOIL ORGANIC MATTER LOSS BY WATER EROSION IN A COFFEE ORGANIC FARM

In tropical regions, water erosion is the process responsible for the redistribution and the loss of soil organic matter (SOM). Modelling can provide a diagnosis of the dynamics of SOM in agricultural production systems, and assist the proposing of conservationist measures. Therefore, this work aimed to estimate SOM losses due to water erosion in an agricultural production system, through the use of modelling techniques. The study area corresponding to the Santo André Farm, located in south-eastern Brazil. The area of the farm is around 75 ha, and the main agricultural product is coffee (78%). The modelling was performed based on the SOM content of the area, and the estimated soil losses, according to the Revised Universal Soil Loss Equation. To the SOM determination, soil samples were collected at 20 points, distributed over the area, in the surface layer (0-20 cm), in March 2018. The parameter acquiring and the data analysis were performed using remote sensing techniques and a Geographic Information System, which was also used to interpolate the SOM content, through the use of the ordinary kriging. The organic matter content on the farm ranged from 1.20 to 2.46%, while the average soil loss was 25.70 Mg ha^-1 year^-1, with higher erosion rates in steepest sites. The estimated loss of total organic matter at 31.87 Mg year^-1, with an average of 0.42 Mg ha^-1 year^-1. The observed results reveal the need to implement conservationist management measures to reduce soil losses, and the consequent SOM losses.