Use of the AGNPS model for identification of agricultural production systems in the Caiuá sandstone subjected to erosion

Abstract

Mathematical models are important tools to evaluate the effect of agricultural production on water
bodies, aiming at reducing environmental degradation. Such models allow the identification of areas subjected
to erosive processes as a result of soil use and management at watershed level, which is preferable for such
investigations. The objective of this work was to adjust the AGNPS mathematical model, in association with
the use of GIS techniques, to predict sediment production in the Inhacanga river, in Altônia, Southern Brazil.
Different scenarios were simulated and the estimates were compared with the measurements during the years of
cultivations, under different rain intensities. The areas with erosion were identified, as well as their causes and
relationships with the changes occurred in soil use and location due to alterations in the agricultural production
system. It was verified that the susceptibility of the areas to erosion increased as perennial crops were substituted
by annual ones and pastures. The increase in the estimated values of sediment production was proportional to
classes of soil water and energy from rain intensity, EI₃₀. The conventional soil tillage techniques resulted in
continuous sediment carriage to the river, independently of the cultivated species.