2.2 Estimates of cost of potential soil losses by water erosion
Potential soil losses by water erosion were estimated considering Brazil’s land use and coverage in 2017 (Table 1). In the areas of annual and perennial crops and planted forest the soil loss was estimated considering a low usage of agriculture conservation practices such as contour tillage, terracing and barriers for water contention and using intensive tillage methods, with deep ploughing, disc harrowing and subsoiling, in which the soil is revolved and exposed to heavy and erosive rains, causing the increase of superficial water runoff (Landers et al., 2006). Also, by considering monoculture for annual crops and lack of cover crops in the perennial (Hernani et al., 2002a). The estimative of annual economic impact of soil losses was based on the revision presented by Eswaran et al. (2001) for crop and pasture areas. The estimation of economic impacts of implementing conservation agriculture (ZT/CA and iCLF-CA) principles towards soil erosion control considered the concepts proposed by Hernani et al. (2002a; 2002b), based on the costs of liming and nutrient replenishment by using fertilizers (organic and mineral), as well as fuel and other inputs.
The modelling of evolution of the conservation agriculture systems (ZT/CA and iCLF-CA) was performed using data from the agricultural census (2017) published by the Brazilian Institute of Geography and Statistics (IBGE). The economic impact of using ZT/CA for an area of 14.4 109 ha was projected as 1.85 109 US dollars, or 129.4 US dollars ha-1 year-1 (Hernani et al., 2002b). For areas with annual crops and ZT/CA, the mitigation of soil loss was considered from an average rate of 5.6 t ha-1year-1 (313.3 million tons in 55.6 million ha) to a value of 2.5 t ha-1 year-1 when using ZT/CA (Hernani et al., 1999). In the case of the adoption of iCLF-CA, it was considering cultivated pastures (not degraded and in good conditions) with an average loss of 13 t ha-1year-1; where the integration of iCLF-CA with the basic principles of ZT/CA reduced soil losses to 2.5 t ha-1 year-1.