Indicadores de qualidade de Argissolo submetido à escarificação em área mecanizada de cana-de-açúcar

Abstract

Soil chiseling conducted only in the planting row is a type of minimal-disturbance soil management practice to prepare fields for planting of sugarcane plantations, and its impact on soil physical quality needs to be evaluated through agricultural experimentation. The objective of this study was to evaluate the physical quality of an Ultisol that was submitted to chiseling as part of sugarcane plantation management. The treatments consisted of soil chiseling only in the planting row (CPR), and chiseling in the total area of the soil of the plantation (CTA). The experiment was carried in Monte Alto, SP, near the coordinates 21º 15 'S and 48º 25' W, average altitude 735 m. Four sampling periods were evaluated. Four periods were evaluated: after soil chiseling, after sugarcane planting, six months after planting, and after mechanized sugarcane harvest. Soil samples were collected within and between planting rows in depths 0.00-0.10, 0.10-0.20, 0.20-0.40, and 0.40-0.60 m. Soil texture was determined along with the following soil physical indicators: bulk density (BD), mechanical penetration resistance (PR), total porosity (TP), macroporosity (MaP), microporosity (MiP). A multivariate factorial analysis was conducted with factor extraction done by the method of principal components analysis. Two extracted factors explained 76% of the total variation. The first factor responsible for 44% of the total variance could be interpreted as the response of soil microporosity formation influenced by the textural nature, since the relevant variables in this factor were MiP, sand and clay. This factor represented the soil intrinsic indicator. The second factor, responsible for 32% of the remaining variance, could be interpreted as the response of the alteration process in the soil mass-volume relationship, since the relevant variables in this factor were MaP, Ds and RP. This remaining factor represented the indicator of soil management.. After factor extraction and using the factorial scores, the index of soil physical quality was determined (SQI), which, together with two factor, aided in the evaluation of soil physical quality. After soil preparation, the planting rows that were submitted to chiseling had better soil physical quality than did the area between the rows that did not receive chiseling in site preparation due to greater pore volume and lower PR and BD. However, the beneficial effect of chiseling did not persist due to subsequent soil reconsolidation, and disappeared soon after the planting of sugarcane, and remained this way up to the post-harvest period wherein the areas within (CPR) and between (CTA) the planting rows had equal soil physical quality.