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) a nd 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 syst ems and positions. After 15 years, the NT treatment achieved greater bulk d ensity and cone index values than CT. This compaction reduced the infiltrat ion rate of NT soil with respect to CT, particularly in the rows between tr ees. Despite that reduction, the NT soil retained a moderate infiltration p otential. That may be explained by the high infiltration rates and macropor osity of the zone beneath the tree, the temporary effects of tillage on inf iltration 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 lo w precipitation, where NT significantly yielded more than CT. The reduction in infiltration in NT must have been compensated by unknown factors that i mprove the tree water supply in drought years. (C) 1999 Elsevier Science B. V. All rights reserved.