Variabilidade Espacial de Atributos Físicos e Químicos de um Antropossolo Decapítico com Aplicação de Água Residuária Tratada

Abstract

Due to the increase of degraded areas, due mainly to anthropic influences, to use alternatives, low cost preferably is necessary, that allow the knowledge the level of degradation and promote the recovery of the soil productive capacity, in order to enable adequate management and recovery of these areas. In this sense, the objective of this study was to evaluate the spatial variability of soil attributes and how it interferes with phosphorus (P) and soil organic matter (SOM) as to verify the effect of treated wastewater (WW), P and SOM contents in a Decapitated Anthroposol. Initially, a georeferencing was performed, a grid was defined and soil sampling was performed in a degraded area with Decapitated Anthropossoil, from which the soil bulk density (BDs), the fine earth bulk density (BDfe), the proportion of the coarse fraction (pCF) and the contents of P and SOM, from these the corrected density (BDco) and P and SOM stocks were calculated. Influenced by the high pCF, the BDs presented extremely high values, in the order of 1.9 kg dm-3. By suggesting a high soil compaction degree BDfe presented values around 1.7 kg dm-3. On the other hand, the BDco was around 1.3 kg dm-3. All physical attributes presented high spatial variability and strong spatial dependence, while P and SOM contents around 3 g kg-1 and 2 mg kg-1 respectively showed high spatial variability and week spatial dependence. The estimate of the P and SOM stock based only on BDs, disregarding the mass and volume of the pCF overestimated the available P and SOM stock in the soil in relation to the same calculation based on the BDco, discounting the pCF. Later, in order to evaluate the effect of the application of treated wastewater on the growth of forest species and the recovery of soil chemical attributes, a randomized block experiment with five forest species irrigated with three water slides (7 L week-1 of (AR7) and 14 L week-1 of treated wastewater (AR14). After three years, the soil was collected and analyzed for P, Organic P and SOM, and the species were evaluated for height and diameter at breast height (DBH). Reaching orders of magnitude 5 to 8 times higher than AA treatment, both AR7 and AR14 treatments promoted an expressive increase in the levels of P, organic P and SOM. However, there was no significant difference in the height and diameter of the forest species among the treatments, probably due to phytosociological factors inherent to the species used. Therefore, RA can be considered as an excellent low cost alternative for the recovery of degraded soils in the semi-arid region.