Propriedades físicas de um latossolo vermelho manejado com material orgânico e submetido à compactação

Abstract

Compaction is a process that changes negatively the soil physical properties and occurs mainly due to intensive use of machinery and implements for agricultural activities. The addition of organic matter in soil is of great importance to minimize this process by increasing the water demand for the soil reaches the optimum moisture content for compaction. To evaluate the change in physical properties of a soil submitted to compaction, when managed with organic material, an experiment was conducted in the laboratory of the Natural Resources Department - Soil Science, FCA/UNESP, Botucatu-SP, assessed by routine and image analysis. The experimental design was completely randomized design, consisting of 32 treatments in a factorial 4x4 double, and, for each organic material (sawdust and BIOMIX®) four compaction levels and four doses of the materials (0, 30, 50 and 80 t. ha -1 ), with four replications. Deformed samples were collected from a clayey Oxisol under forest in the layer from 0 to 20 cm. The moisture for maximum soil compaction was obtained using the Standard Proctor test. Soil samples were sieved, mixed with doses of organic materials, incubated for 30 days, sieved again and the water content adjusted to 27%. Sub samples were put in PVC tubes and compressed with the aid of a hydraulic press in order to obtain the desired compaction levels. The physical properties evaluated were soil bulk density, porosity, macroporosity, microporosity, soil penetration resistance and hydraulic conductivity. In addition to the routine method, the evaluation of the compaction effects on macroporosity was done by image analysis acquired from samples after the resin impregnation in the soil samples. The images taken with digital camera were processed in the Visilog 5.4. Statistical analysis was performed using Sisvar version 4.6 (2003), resulting in the analysis of variance and regression test and mean comparison (Tukey) for the effect of different doses and different compaction levels and the interaction between them. Comparisons of means were performed using the F test at 5%. The compaction process negatively alters soil density, soil resistance to penetration, the total porosity, macroporosity and hydraulic conductivity. The addition of organic matter improves soil physical properties and minimizes the effects caused by compaction.The dose of 30 t ha -1 of organic material is sufficient to reduce the negative effects of compaction on soil physical properties. The image analysis allows the identification of changes in soil porosity resulting from compaction, especially on the type and size of pores. The compaction causes reduction of large pores and complex, and increase of small pores and rounded. Soils at doses of 50 t ha -1 and 80 t ha -1 of BIOMIX ® have improved connectivity between pores and increase pore complex.