Effects of tillage method on soil physical properties, infiltration and yield in an olive orchard

The long-term effects of two different tillage systems, conventional (CT) and no tillage (NT), were studied in an olive orchard in Santaella (Southern Spain) for 15 years. In both tillage systems, two distinct zones developed in the orchard in relation to soil physical properties; one underneath the tree canopy, and the other in the rows between trees. Surface soil organic matter content, bulk density, cone index, macroscopic capillary length and hydraulic conductivity showed significant differences between tillage systems and positions. After 15 years, the NT treatment achieved greater bulk density and cone index values than CT. This compaction reduced the infiltration rate of NT soil with respect to CT, particularly in the rows between trees. Despite that reduction, the NT soil retained a moderate infiltration potential. That may be explained by the high infiltration rates and macroporosity of the zone beneath the tree, the temporary effects of tillage on infiltration and probably by the self-repair of soil structure in the Vertisol studied. Yield was not affected by tillage except in one year with very low precipitation, where NT significantly yielded more than CT. The reduction in infiltration in NT must have been compensated by unknown factors that improve the tree water supply in drought years. (C) 1999 Elsevier Science B.V. All rights reserved.