Pedological features as indicators of the tillage effectiveness in Vertisols

Abstract

Several agroecosystems in Mexican soils show a severe physical degradation as a consequence of excessive energy use during tillage. The purpose of the present paper was to assess the main physical properties and the fabric of an Eutric Vertisol managed with traditional (TT) and minimum (MT) tillage systems and compare them with those of the same soil under secondary vegetation (Vn). Disturbed and undisturbed samples were obtained at 20 m intervals at five locations along selected transects in each of the three experimental plots. The undisturbed samples were used for the structural analysis. The Vertisol showed different structural arrangements under Vn, MT and TT, as well as a clear tendency towards soil compaction in the furrows of MT. The entropy of the structural systems turned out to be a precise indicator of the changes in soil structure effected by tillage. The entropy of the structural system was at a maximum (0.66) under Vn, less under TT (0.61) and at a minimum in the furrows between beds under MT (0.50). As the entropy values provide information about the soil structure in situ, we can say that minimum tillage produced a considerable compaction of Eutric Vertisol. However, soil water retention was 12% higher under Vn. Saturated hydraulic conductivity ( K s) was higher under Vn than under TT and MT treatments. The different management systems influenced the composition, shape, and distribution of the pedological features in this Eutric Vertisol. The morphology of iron nodules showed that with TT the flow rates of the iron-rich solutions were higher and the conditions for ion precipitation were more favorable than in the other two systems. The drainage conditions improved with traditional tillage.