Slash-and-burn agriculture: Establishing scenarios of runoff and soil loss for a five-year cycle

Shifting cultivation is an age-old agricultural system that coexists with modern agricultural systems, particularly in the tropics. The characteristics and effects of shifting cultivation are well documented in the literature, including: soil degradation and erosion, nutrient depletion, impacts on biodiversity, and economic trends. Although studies report soil loss during the cropping period under shifting cultivation, few studies have assessed soil erosion during a full slash-and-burn cycle. The objectives of this study were to characterize runoff and soil loss for a full 5-year regeneration cycle in a slash-and-burn system. The measurement of runoff and soil loss was based on three replicate 2-m2 plots installed in each monitored area. Three agricultural plots in different stages of regeneration were monitored. The data were analyzed by month and year for the 5-year regeneration cycle. Runoff and soil loss decreased exponentially from the burned phase to the early stage of secondary forest. Runoff and soil loss exhibited patterns similar to those of a forested area after only 4–5 years of regeneration. In general, areas undergoing slash and burn in the Guarapuava region are stable and the fallow length, as well.

► An exponential decrease in soil loss occurs after a sudden increase due to fire. ► Soil loss after burning accounted for 56% of total period. ► Runoff-soil loss was similar to a forested area just after 4 years of regeneration. ► Soil loss in the regeneration cycle, is within the tolerance limit for shallow soil. ► The soil-loss tolerance limit would be exceeded for a 3 years regeneration cycle.