LOOSENING OF A SILT LOAM SOIL: EFFECTS ON PHYSICAL PROPERTIES

Abstract

No-tillage systems tend to reduce the negative impacts of agriculture on soil, not only by the absence of tillage, but also by the presence of permanent cover. There is abundant evidence regarding processes of physical degradation (densification) determined by successive years of farming under this system, particularly in soils with high susceptibility to compaction (silty loams soils). The objective of this work was to evaluate the effects of decompaction of a silt loam soil under continuous no-tillage systems on some physical properties and their persistence. Completely randomized plots with two treatments were used: 1) no tillage with soil loosening, and 2) a continuous no-tillage system. The parameters evaluated were: bulk density, mechanical strength, gravimetric moisture up to 30 cm depth determined at intervals of 5 cm, and basic water infiltration. Bulk density showed no significant differences between treatments. The mechanical strength allowed the identification of densified layers that were observed in the field, and showed significant differences in all depths up to 4 months after loosening. Eight months after loosening, these effects only persisted in the layer 10- 20 cm, while a significant increase in the basic infiltration rate (134%) was observed in the subsoiling treatment compared to the control. It was concluded that basic infiltration rate and mechanical
strength were sensitive parameters to assess the persistence of the effects of soil loosening.