Effect of tillage systems on soil aggregation and hydraulic properties in SW Spain

Abstract

Conservation tillage is particularly important in arid and semi-arid zones, where water is the limiting factor for crop development under rainfed conditions. Conservation tillage improves physical properties and increases organic matter of soils under Mediterranean conditions. This work studies the influence of two tillage systems (traditional tillage, TT, and conservation (reduced) tillage, RT) on soil hydraulic properties and on soil aggregation after 15 years of experimentation. The effect of no-tillage (NT) in a short-term experimentation (4 years) was also considered. In the long-term experiment, the aggregate size distribution (ASD), mean weight diameter (MWD) and aggregation index (AI) values were greater in RT than in TT, although differences were not significant. Water stability (WAS) values for 1-2 mm size aggregates were greater in TT, despite the organic carbon (OC) and CaCO3 contents in these aggregates were greater in RT. However, under our conditions NT seems to have a greater effect on WAS. The increase of this variable in NT respect to TT, was observed after only three years of experimentation. In the long-term experiment, the hydraulic conductivity was higher in TT than in RT for h > -20 mm in agreement with a greater characteristic mean pore radius for h > -20 mm. In the short-term experiment, the lower hydraulic conductivity in NT than in TT suggests a lack of interconnected pores in NT treatment.