Labor profunda en siembra directa: Efecto sobre la condición biológica del suelo

Abstract

El suelo es uno de los ecosistemas más complejos y diversos que existen en la naturaleza. Es un ambiente que combina las fases sólida, líquida y gaseosa formando una matriz tridimensional. La compleja naturaleza físico-química, su estructura porosa y el contenido de materia orgánica en diversas fases de descomposición y complejidad, proporcionan una heterogeneidad trófi ca y de hábitat que permite en él la coexistencia de una gran diversidad de organismos (Zerbino y Altier, 2006). El ciclo de los nutrientes, junto con la estructura edáfi ca y otras propiedades del suelo, son sustancialmente reguladas por la actividad de una comunidad de microorganismos y diversas especies de invertebrados (Lavelle, 1997). El uso del suelo con fi nes productivos genera alteraciones en la interrelación de las propiedades edáfi cas. En las últimas décadas en la región pampeana de Argentina se produjo un cambio importante del uso del suelo. Este cambio estuvo asociado con el incremento del área cultivada con soja, lo que alteró las condiciones biofísicas de los suelos de la región pampeana. Con la introducción de cultivares de soja Labor profunda en siembra directa: Efecto sobre la condición biológica del suelo Abstract C. Alzugaray, M.S. Vilche, and C. Petenello. 2008. Deep tillage in the no-till system: Effects on the biological condition of the soil. Cien. Inv. Agr. 35(3):265-276. The no-tillage system offers the advantages of greater stability and biological diversity, although it may generate soil compaction. This mechanical restriction can be solved with deep tillage, which is able to generate loosening that preserves the superfi cial covertures. The biological condition of soil is very sensitive to disturbances resulting from tillage. The objective of this study was therefore to evaluate changes in the biological condition of soil that are caused by the use of paratill under no-tillage lots. The experiments were conducted using corn crops in Zavalla, Argentina (60º 53´W and 33º 01´S), in a vertic Argiudoll. The treatments included no-tillage and no-tillage with paratill. The following parameters were assessed: soil organic carbon, nitrates, sulfates and phosphorous; biomass and microbial respiration activity; meso-and macrofauna; root channels; sites with fungi and decomposed organic matter; krotovinas and root system depth at the fi ve-leaf stage of cultivation; and aerial and root dry matter. The data were processed by uni-and multivariate analysis. The decompaction generated by paratill was found to impact the soil's biological condition under no-tillage. Paratill promoted the development of root systems without signifi cantly impacting the biomass of the corn. In addition, it created an edaphic environment that conditioned those processes that regulate the microbial population. Moreover, paratill stimulated the dynamics of the organic matter without modifying the fauna of the soil, which settled down during the period of implementation of the no-tillage system. The multivariate methods were suffi cient to integrate the various attributes of the system.