Groundcovers in Olive Groves in Semiarid Climates: Are They Always Beneficial?

Abstract

Olive groves on the Mediterranean Basin are usually managed by continuous tillage and low organic matter inputs, leading to several soil degradation processes. Groundcovers (GCs) have come out as an alternative soil management strategy to improve soil’s fertility, soil’s organic matter quantity, and the sustainability of agro-ecosystems. Nevertheless, farmers are still unwilling to implement GCs or reduce tilling frequency while there are still some uncertainties and lack of global analyses. The purpose of this study was to perform an assessment of the effects of using GC on the soil parameters microbiological biomass, crop yield, and olive oil quality. A field trial was performed on a gypsiferous soil in central Spain with three different GCs: permanent GC of Brachypodium distachyon (BRA); permanent GC of spontaneous vegetation (SVE), and annual GC of Vicia ervilia (BIT) to be compared with conventional tillage (TIL). After three years, numbers of nematodes, fungi, and bacteria were higher on plant roots regardless of GC composition. BRA was the treatment with the biggest impact on soil and yield parameters. BRA increased soil organic carbon 1.03 Mg ha−1 yr−1 at 0–10 cm depth but reduced significantly olive yield because of nitrogen competition. The BIT treatment improved soil organic carbon stocks and soil structure, and did not reduce olive yield significantly regarding TIL. The BIT treatment was considered the best soil management strategy in semiarid conditions.