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Soil physical and mechanical attributes and its relationships with vegetal residues and matter content in areas cultivated with sugarcane

Abstract

The mechanical harvest of sugarcane allows the maintenance of a layer of vegetal residues in the surface of the soil, leading to the enrichment of the superficial layers with organic matter, which may reduce the process of compacting and its consequences, since the vegetal residues in the surface can attenuate the pressures produced for machines. Therefore, the objective of this work will be to study the alterations in the physical and mechanical behavior of soil caused by the enrichment with organic matter and, besides, to study the capacity of the vegetal residues accumulated in the surface of the soil of dissipating loads in areas cultivated with sugarcane and managed with and without burning. The project will be developed in three areas cultivated with sugarcane and submitted to the following management practices: 1- manual harvest followed by burning of residues since 1973; 2- mechanical harvest without burning since 2004 (3 years of implantation of the system of green cane); 3- mechanical harvest without burning since 1996 (11 years of implantation of the system of green cane). The following physical attributes will be evaluated in the depths of 0.00-0.10 m, 0.10-0.20 m and 0.20-0.30 m: particle size, soil consistency, retention curve, bulk density, aggregate stability, soil porosity and soil resistance to penetration. The least limiting water range will be determined in order to identify the critical limits of bulk density where the soil resistance to penetration and the aeration porosity are restrictive to the development of the plants. Also, the relationship between organic matter content and soil compressibility, the relationship between soil organic matter content and critical humidity for soil compaction and the relationship between the amount of vegetal residues in the surface and the bulk density will be evaluated by the Proctor test. The data of bulk density, aggregate stability, soil porosity and soil resistance to penetration will be submitted to geostatistics analysis in order to evaluate the spatial variability and confection of kriging maps. Also, relative analyses of regression between the physical attributes and the assay of compressibility and the adjustment of equations between the organic matter content and optimum humidity, maximum bulk density, soil resistance to penetration and productivity of the sugarcane culture will be performed. (AU)