Atributos físicos, químicos e biológicos do solo em pastagens sob uso sucessivo de dejeto líquido de suínos

Abstract

This study aimed to: i) develop a characterization of the microbial community; and, ii) characterize, quantify, and map the distinct patterns of spatial variability of soil biological attributes in pasture areas without and with successive use of swine manure (DLS) over the medium and long term, in addition to: iii) analyze the effect of successive use of DLS over the medium and long term in different landscape positions (upper, middle, and lower thirds) on the soil's physical-hydric, chemical, and biological attributes. Three treatments were evaluated: pasture soil with medium-term (A12) and long-term (A23) use of DLS, as well as native grassland (CN), and for microbiological analysis, the DLS itself was considered as a fourth treatment. In the article I, it was concluded that the use of DLS, as well as the duration of its use, stimulated the diversity and abundance of bacteria, but negatively affected these same parameters when considering the fungal population. In article II, increases in saturated hydraulic conductivity (Ksat) were observed in Tsup of CN, while A23 showed higher organic carbon contents (COT) throughout the area, with greater emphasis in Tinf at the surface soil depth. The most sensitive attributes to the use of DLS were: Ksat, COT, and the soil water retention curve (CRAS), with notable improvements in A23 compared to A12, with minimal changes in landscape positions regarding CRAS. In article III, it was concluded that long-term use of DLS (A23) increased soil acidity, as well as the levels of MO, P, and K, along with the heavy metals Zn and Cu, while reducing Ca and Mg levels, with more pronounced effects in Tinf. The long-term use of DLS (A23) also increased the diversity and abundance of soil biology, along with increases in the activity and dry biomass of soil fauna, with greater emphasis in Tinf of the landscape, indicating percolation of DLS after application, leading to higher concentrations in the lower landscape positions. In article IV, it was observed that medium- and long-term use of DLS affected the patterns of abundance, richness, and indices, favoring a higher occurrence of Collembola, Orthoptera, and Thysanoptera, as well as the abundance and richness of groups. Geostatistical techniques effectively analyzed the spatial dynamics of soil fauna, demonstrating similarity in the spatial variability patterns of the groups and indices, with shorter ranges in A23. In article V, the application of DLS negatively affected the soil quality index (IQS) over time in an increasing manner. The areas with DLS use (A12 and A23) showed chemical degradation, due to slight soil acidification (A23) and the levels of available phosphorus being above the Environmental Critical Limit (LCA-P) calculated for each area, representing a high potential for environmental impact.