Efecto del sistema de laboreo y manejo de residuos sobre la estabilidad de los agregados en un oxisol (Brasil)

Résumé

Tillage systems and inadequate management of crop residues may cause temporary or permanent changes in soil structure. In this survey was assessment the infl uence of the tillage and crop residues management on structural stability in a soil of savanna transformed in agricultural land. During fi ve years was established a crop rotations consisting of beans/cover crops/soybeans under two management systems: conventional tillage (CT) and no-tillage (NT). we assesment the infl uence of tillage and management of crop residues on the structural stability, using the size distribution of water stable aggregates and by the mean weight diameter(WMD). In all treatments, the largest proportion of aggregates was in the class > 4mm, although LC and NL decreased between 13 and 56% compared to the natural soil. Tillage systems differed in the ability of soil aggregation. The MWD in conventional tillage was signifi cantly higher than in no-tillage systems. This fact was related to the time of sampling and also with phenomena of compression. Among the cover crops crotalaria (Crotalaria juncea), guandu (Cajanus cajan) and millet (Pennisetum americanum) showed positive effects on the stability of aggregates when are cultivated under no-tillage systems.