4.1 Land Use and Occupation
The predominant crops in the inspected sections of the watershed were Pasture, Natural Forest and Coffee. The natural forest, considered the best vegetation cover, is present in an area corresponding to 21.16% of the surface of this stretch of Rio do Peixe watershed., In a watershed of 11,000 ha in Botucatu, with relief similar to Rio do Peixe watershed, Santos et al. (2014) found 1,109 ha of natural forest, corresponding to 9.95% of the watershed area. These results correspond to less than half of the results of the present work, indicating that, in this stretch of Rio do Peixe watershed, the forest is much more preserved.
In what concerns the pasturs of the studied area, there is an occupation of 30,472 ha, amounting to 60.81% of the total area of the watershed (Table 1). Such results are similar to those of Lima et al. (2004), who inspected 43,228 ha of pasture in a watershed in Ilha Solteira, SP, where it amounted to 66.79% of the total surface. In this work, one of the positive examples was the restoration of an agricultural property in Ocauçu, SP, with a degraded pasture area of 500 ha. After carrying out this work, these 500 ha were transformed into an agricultural area with no-tillage system, intended for annual crops, with rotation: brachiaria straw, soybeans, corn and wheat in winter (crop change and soil management). This represents the implementation of a new conservationist technology in the region.
4.2. Vegetation Cover Indicators
The images from Google Earth® Pro confirmed the effectiveness of the actions implemented in the pasture area where an erosive process had taken place (Figure 2A and 2B). An plan of agri-environmental adequacy was applied, to contain the erosive processes and control the erosion in the area, which was accomplished with the construction of containment basins on the pasture areas. There was an improvement in the visual aspect of the area, compared to soil conservation strategies, in which case it was proven that pasture management with the use of containment basins favored the restoration of the area, and the return of potential soil productivity.
Figures 2C, 2D, 2L and 2M effectively demonstrate that the change in management of coffee plantations provided a positive change in the landscape. In addition to improving the landscape with more intense vegetation cover (Figures 2D and 2M), there was an improvement in potential crop productivity. In the coffee culture, what contributed to the improvement of the soil conditions was the adequacy of the crop to the relief, and recovery of soil fertility. The soil conservation techniques applied in this case were sufficient to control the erosive processes.
Image comparison of Figures 2E and 2G showed that the agricultural terracing built in the area under scrutiny was efficient in controlling erosion processes at the property. According to Araújo et al. (2009), with the use of appropriate management measures and erosion mitigating actions, along with the restoration of the impacted areas, there will be an improvement in water quality and control of sediment production, minimizing silting and consequently, there will be an almost complete environmental restoration.
The comparison of aerial images, from before (T1) and after (T2) the treatment, was used to assess the efficiency of the results obtained. The same method was used by Bezerra et al. (2012), who used it to compare the vegetation cover and the water potential in the soil, with the purpose of monitoring and restoring degraded areas. The photographic comparison, in addition to a supervised classification, allowed to monitor the development of the vegetation cover with grasses, as well as their relation to the soil’s water potential. According to Menezes et al. (2009), the use of remote sensing permitted the identification of areas already affected by inadequate management, with degraded pastures. These authors also highlighted the fact that native vegetation has been largely converted into pasture. Figures 2K and 2O illustrate the mechanical control of erosions, as the construction of dams and terraces transforms the previously degraded landscape into a pasture with productive capacity (Figures 2J and 2N). Figure 2J shows an old and eroded road that carried sediments to the bed of Rio do Peixe, and which was corrected with the construction of terraces (Figure 2K).
It is noteworthy that there are practices focused on the conservation of pastures, which represent a large part of the Rio do Peixe watershed section in addition to promoting important benefits for soil conservation. This can further enhance the income for producers since, with conserved pasture, there is a higher volume of biomass and, consequently, a chance for higher animal density. An example of this is the case of pastures recovered by Integrated Crop-Livestock Systems (LIS) where the management was modified through the replacement of the varieties of grass, and by providing pasture with quality plant mass during the dry periods. This resulted in an occupancy rate of five Animal Units (AUs) per ha, as evidenced by the evaluation of 10 properties, where there was an average growth of 31% in the occupancy rate, compared to the original situation, i.e. before carrying out the inspection work. This is corroborated by the study of Albernaz & Lima (2007) who evaluated two sub-watersheds occupied by pastures in Lavras, MG, adopting conservationist practices: level planting, terracing, containment basins and liming maintenance. They have also suggested that at Ribeirão Santa Cruz sub-watershed (SW), more conservation practices are adopted than at SW Água Limpa, and the exposure of the soil to degradation was higher at SW Água Limpa. A similar result was observed by Zolin et al. (2011), who documented that the largest relative reductions in soil loss occurred under scenarios of conserved pasture, indicating that the optimization of soil conservation can be accomplished by adopting conservationist management practices for pasture recovery. According to Rodrigues et al. (2015), who analysed the role of vegetation in water interception and erosion control, at Rio Paraíso watershed, in São Manuel, SP, and the uncovered soil showed a 98.09% increase in sediment production, when compared to soils with vegetation cover.