Perdas e custos associados à erosão hídrica em função de taxas de cobertura do solo

Abstract

The aim of this study was to estimate water erosion costs associated with nutrient losses in four different rates of artificial cover. The experiment was carried out from 1987 to 1996 in runoff plots to measure soil losses in Campinas, State of Sao Paulo, in an Ferralsol under natural rainfall. The experimental design was completely randomized, with four treatments (0%, 24%, 40% and 90% artificial cover) and three replications. To estimate costs, P, K + , Ca 2+ and Mg 2+ concentrations in runoff water and soil removed by erosion were summed up, converted into triple superphosphate, potassium chloride and dolomitic limestone and multiplied by their respective market prices. The results indicate that, under the experimental conditions, the greater the percentage of soil cover, the lower the losses of water, soil, organic matter and nutrients. The soil with 90% cover presented reduction of 51.97% in average water losses, 54.44 in soil losses and 54.91% in organic matter losses than the treatment with 0% cover. In bare soil, losses were estimated at 16% P 2 O 5 and 8% KCl in terms of the amount of fertilizers recommended. Costs varied from US$ 107.76 ha -1 year -1 in bare soil (0% cover) to US$ 18.15 ha -1 year -1 in soil with 90% cover. With these values, losses were estimated at 616.5 million tons of soil per year for Brazil, as a result of soil erosion in annual crops, and cost of this process is around US$ 1.3 billion per year.

Nutrient and Organic Carbon Losses, Enrichment Rate, and Cost of Water Erosion

“…Taking into account that P is potentially the element causing eutrophication of surface waters, the likely place of deposition of fine sediments carried by water erosion (Shigaki et al, 2007), this is a serious problem. Moreover, it is important to consider that losses of P, other elements, and OM by water erosion are responsible for soil depletion and increased cost of agricultural production (Dantas and Monteiro, 2010;Dechen et al, 2015).…”

“…In studies carried out in other countries, it was shown that the total cost of these losses was higher in CT than in NT (Hart et al, 2004). In Brazil, some studies showed that this value was greater in NT than in CT (Bertol et al, 2007b), others showed the opposite (Dantas and Monteiro, 2010), and others showed that increased soil cover decreased the amount of losses (Dechen et al, 2015), thus establishing a contradiction. Knowledge of the cost of nutrient losses through erosion is important in helping convince farmers to adopt effective conservation practices to reduce erosion and its cost.…”

“…An increase in tillage intensity degrades the physical properties of the soil, reduces water infiltration, and increases water erosion, which impoverishes the soil in its place of origin and contaminates the environment outside that site (Koski-Vähälä and Hartikainen, 2001;Hart et al, 2004;Bertol et al, 2007b;Shigaki et al, 2007;Coletti et al, 2010). Erosion also implies costs, due to loss of nutrients and soil amendments (Bertol et al, 2007a;Andrade et al, 2011;Duan et al, 2011;Pugliesi et al, 2011;Dechen et al, 2015).…”

“…According to these authors, the fertilizers applied and crop residues maintained on the soil surface due to absence of tillage in NT are responsible for these conditions. With water erosion, increased losses of nutrients and organic matter occur since these nutrients and organic matter are concentrated at the soil surface (Bertol et al, 2007b;Dantas and Monteiro, 2010;Pugliesi et al, 2011;Dechen et al, 2015).…”

“…The total losses in regard to plant nutrients and limestone by water erosion represent cost (Bertol et al, 2007b;Duan et al, 2011;Dantas and Monteiro, 2010;Pugliesi et al, 2011;Dechen et al, 2015) because they need to be replaced in the crops through use of fertilizers (Pugliesi et al, 2011), raising the cost of agriculture. This cost is usually not taken into account by farmers, due to lack of knowledge.…”