Atributos químicos e matéria orgânica do solo sob diferentes sistemas de uso e manejo em ambientes de floresta de Roraima

Abstract

The crop-livestock integration systems (cLI) crop-livestock integration forest (cLIF) and pasture have emerged as strong alternative to carbon incorporation and consequently improvement in physical and chemical characteristics of the soil. The objective of this work to evaluate the chemical attributes, organic matter in soils under Natural forest undertaken in different use systems and soil management: pasture (PAST), crop-livestock Integration (cLI) crop-livestock Integration forest (cLIF) and a Natural forest (NF) as a witness. The experimental design was completely randomized in plots scheme subdivided, with 24 treatments from the association between four systems and six different depths (0-10, 10-20, 20-40, 40-60, 60-80 and 80-100 cm), with four repetitions. The data subjected to analysis of variance, and significance through "F", the averages compared by Tukey test at 5% probability of error. cLI systems and PAST showed similarities in chemical attributes such as pH, Ca2+, Mg2+ and K+. pH showed no difference between the studied systems. For potential acidity (H + Al) the highest value for this variable was found in the cLIF area at a depth of 0-10 cm and the smallest in the pasture. Aluminum (Al3+) was superior in the NF. The sum of the bases (SB) presented the highest value in the PAST system. The saturation by bases (V %) was higher in the PAST in all the depths evaluated, and lower in the NF. The total cation exchange capacity (TCC), showed the highest value in the area of cLI in the depths 0-10 and 10-20 cm and the smallest values in the cLIF area at the depth of 20-40 cm. The chemical fractionation of soil organic matter (SOM) revealed that the cLIF area had the major value for Humina (HUM) and humic Acid (HA). The FN presented greater value for Fulvic acid (FA). The NF presented the largest value for Fulvic acid (FA). The particulate organic carbon (Cop) was greater at all depths in the PAST area. The organic carbon associated with minerals (Coam) presented the highest value for all systems in general in the 0-10 cm depth. The total organic carbon (TOC) was greater among the systems assessed in relation with the NF. Oxidizable fractions showed similar values in the lighter fractions (F1) and (F2), however, regardless of the evaluated area, it observed a predominance of the most recalcitrant fractions of MOS (F3) and (F4). The analysis of carbon stocks showed no significant difference but presented best values between systems in relation to FN. After this results, its concluded that management systems deployed showed higher values of Ca2+, Mg2+, Na+, and P in the surface layer (0-10 cm) of soil in relation to the NF. Humic substances (HA), (HUM) and the physical fractions (Coam) showed greater stability in management systems. The ratio AH/AF was greater in the PAST area and a reduced amount of in the cLI indicating that organic matter from ecosystems presents greater stability on the ground. The (HUM) showed higher levels, regardless of the area studied and analyzed depths. Therefore, the management systems evaluated positively influenced in the dynamics of the MOS when compared with NF.