Quantification of critical agricultural operation and vertical stress distribution in the soil by machines used in sugarcane cultivation

Abstract

Soil compaction in sugarcane agroecosystems, caused by the intense traffic of machines through the crop cycle, has been pointed by farmers as a limitation for maintaining productivity and longevity of sugarcane plantations. Aiming to find ways to reduce the harmful effects caused by the agricultural traffic on soil structure, the objectives of this project are: a) to evaluate soil structural alterations in the sugarcane cultivation system by monitoring compaction and physical quality of the soil after each agricultural operation carried out; b) to determine the possible additional compaction provided by the traffic during the sugarcane harvesting operations performed with a single and a double line harvesters, by means of the preconsolidation pressure (Ãp) and c) to measure the maximum soil tensions and its distribution caused by the traffic of agricultural machinery at different levels of straw kept on the soil surface after harvest. The project is composed of two experiments: the first has a randomized block design (DBC), with three replications and the following treatments: two types of soil, two mechanized harvesting systems (using single and double line harvesters) and different water contents during cane harvesting (at field capacity and below field capacity). The second experiment is a DBC, with three replications in a factorial scheme (2x2). The factors are: two types of soil and four amounts of cane straw (0, 5, 10 and 15 Mg ha-1 dry mass). Soil quality indicators (soil density, porosity, penetration resistance, relative density and preconsolidation pressure) will be evaluated and soil compression curves (CCS) estimated. It will be also measured the tensions applied to the soil by the machinery used in the sugarcane harvesting system. The preconsolidation pressure values (Ãp) will be adjusted as a function of the volumetric moisture, to produce the soil load bearing capacity models (MCSC). The comparisons among CSC for treatments will be performed by the F test, as described in previous works on soil mechanics. Physical-water and mechanical soil attributes data will be submitted to analysis of variance, and the means compared by Tukey's test (p = 0.05). (AU)