Compactação e qualidade física do solo em sistemas de colheita mecanizada e semi-mecanizada de cana-de-açúcar

Abstract

The decrease in sugarcane production, throughout the cycles, may be linked to the increase in gaps and loss of soil physical quality and this is related, among several factors, to soil compaction, the traffic of agricultural machinery in the harvesting phases, as well as the direct damage to the sugarcane stalks. When this traffic is carried out without control or adjustment to the plantation, the machines travel not only between the sugarcane lines, but also over the sugarcane lines, increasing the risk of compaction and loss of soil quality, which involves changes in the physical properties of the soil, increased density and soil penetration resistance. These soil properties usually respond with high variation, making it difficult to understand compaction, because, in addition to this variation, different factors affect compaction, such as: soil use and management, spatial-temporal variation, texture, etc. Several techniques have been used (classical statistics, geostatistics) for their study, but it is still necessary to use other techniques, such as, for example, the multifractal analysis that allows to evaluate these responses at multiple scales. In this sense, the objective was to compare the physical-mechanical changes of the soil, the physical quality of the soil, the occurrence of gaps, in different phases of the sugarcane and the multifractality of the soil penetration resistance and moisture under different harvest systems. In an 18 ha plot, two 1 ha areas were elected to compare the compaction of the soil and the occurrence of gaps, in different phases of sugarcane and under mechanized and semi-mechanized harvesting. For the evaluation of the compaction, the density, water content in the soil, macroporosity, water available for the plants, penetration resistance and organic carbon content, were mainly analyzed; the occurrence of gaps was also evaluated by determining the number, size and percentage of gaps. After the first sugarcane harvest, the traffic in the semi-mechanized system caused mainly an increase in soil density, penetration resistance and decrease in macroporosity, causing reduction in soil physical quality, mainly in the capacity to support root growth. This reduction in quality had a negative correlation with the increase in the occurrence of gaps in sugarcane, showing an increase of 30% in gaps with the first harvest. Fractal analyses showed multifractal environments of penetration resistance and water content in the soil, highlighting that after the semi-mechanized harvest traffic homogenized the scales of values making the responses monofractal.