Enzymatic activities under different cover crop management in a Mediterranean olive orchard

Abstract

The aim of the present work was to determine the long-term effects of cover crops on organic carbon and soil enzyme activities at three different soil depths in a Mediterranean olive orchard in south-east Spain. The management practices assayed were (1) sowing of an annual cover of vetch, crushing it at blooming and leaving the debris on the soil surface, (2) the same but mixing the debris into the soil by chisel ploughing and (3) ripping of annual weed cover and mixing it into the soil by chisel ploughing. For comparisons, adjacent plots under integrated production management that received mouldboard ploughing and disk harrowing were included. The cover crop treatments showed higher values than did the integrated treatment for organic carbon and all enzymatic activities in the superficial layer (0–5 cm), and the highest values were found under annual cover treatment leaving the debris on the soil surface. All treatments showed a clear gradient in the organic carbon and enzyme activities with depth. There was no significant difference in the organic carbon and ß-glucosidase at the intermediate layer (5–10 cm). At the deepest layer evaluated (10–20 cm), only dehydrogenase and alkaline phosphatase were higher for the cover treatments. This study revealed that the use of cover crops could be the best option when organic olive orchards are managed on slopes in a Mediterranean climate.