Estimates of Annual Soil Loss Rates in the State of São Paulo, Brazil

Abstract

Soil is a natural resource that has been affected by human pressures beyond its renewal capacity. For this reason, large agricultural areas that were productive have been abandoned due to soil degradation, mainly caused by the erosion process. The objective of this study was to apply the Universal Soil Loss Equation to generate more recent estimates of soil loss rates for the state of São Paulo using a database with information from medium resolution (30 m). The results showed that many areas of the state have high (critical) levels of soil degradation due to the predominance of consolidated human activities, especially in growing sugarcane and pasture use. The average estimated rate of soil loss is 30 Mg ha -1 yr -1 and 59 % of the area of the state (except for water bodies and urban areas) had estimated rates above 12 Mg ha -1 yr -1 , considered as the average tolerance limit in the literature. The average rates of soil loss in areas with annual agricultural crops, semi-perennial agricultural crops (sugarcane), and permanent agricultural crops were 118, 78, and 38 Mg ha -1 yr -1 respectively. The state of São Paulo requires attention to conservation of soil resources, since most soils led to estimates beyond the tolerance limit.

Diagnosis of the Accelerated Soil Erosion in São Paulo State (Brazil) by the Soil Lifetime Index Methodology

“…The results of the estimated soil loss rates used in this study were obtained by Medeiros et al (2016). These authors describe the limitations of the USLE and the generalization of some factors caused by adaptation of the methodology to a regional scale.…”

“…This study considered the estimated soil loss rates (Mg ha -1 yr -1 ) for the state of São Paulo at medium resolution (30 m), previously obtained by Medeiros et al (2016) (Figure 3). The results were obtained by the Universal Soil Loss Equation (USLE) (Wischmeier and Smith, 1965;1978).…”

“…This study addressed the whole area of the state of São Paulo (Figure 1 by intense agricultural use has damaged many areas in the state (Medeiros et al, 2016). From the biophysical point of view, the state is part of the regional complex Southeast which comprises a wide variety of soils, for being located in the transition region between the semi-arid ("Drought Polygon", in the North of Minas Gerais) and humid climate (coastline and mountains, including the Serra do Mar and Serra da Mantiqueira), as well as an extensive sedimentary region in the highlands to the West of the mountainous areas (Lepsch, 2010).…”

“…Initially, the soil loss rates (A, in Mg ha -1 yr -1 ) estimated by Medeiros et al (2016) were converted into thickness of the lost soil layer (h, in mm yr -1 ). This conversion was calculated from the bulk density (Bd, Mg m -3 ) (Figure 2b), according to equation 1.…”

“…Data published by the soil conservation section of the Instituto Agronômico de Campinas/Agência Paulista de Tecnologia dos Agronegócios in the 1980s indicated an annual soil loss of 130 million tons in the state of São Paulo, representing about 25 % of the soil loss throughout Brazil (Bertoni and Lombardi Neto, 2012). These soil loss data were updated by Medeiros et al (2016) and the authors reported that the annual loss in the state reaches about 600 million Mg yr -1 . Moreover, it is estimated that the erosion tolerance limits are exceeded in 80 % of the cultivated areas (CDA, 2014).…”