Site‑Dependent Effects of Cover Crops on Soil Properties and Enzyme Activities in Semiarid Olive Systems (SANCHOSTHIRST PROJECT)

The EJP Soil SANCHOSTHIRST project (Cover cropS and soil health and climAte CHaNge adaptatiOn in semiarid woody crops: Remote Sensing and scenario projections) investigates the potential benefits of alternative soil management practices compared to traditional tillage in woody crops. Previous studies within the project have evaluated the effects of cover crops on soil enzymatic activities. Building on this work, the present study examines how different soil management strategies influence key soil enzyme activities across five olive‑growing locations in Spain included in the SANCHOSTHIRST network.

At each location, two adjacent plots were sampled: one managed with cover crops and the other under conventional tillage. In both plots, three composite soil samples were collected at two depths (0–10 cm and 10–30 cm). Samples intended for biological analyses were kept refrigerated from sampling until enzymatic determinations were performed. The enzymes analysed represent major biogeochemical cycles: β‑glucosidase (C cycle), urease (N cycle), phosphatase (P cycle), and arylsulfatase (S cycle). The physico‑chemical variables measured included pH, electrical conductivity, carbonate content, available ammonium, available nitrate, available phosphorus, soil organic carbon, particle‑size distribution (sand, silt, clay), and bulk density. Variables related to vegetation present in each plot were also considered. One‑way ANOVA and multiple linear regression analyses were performed to assess the influence of soil management on the measured variables and to identify the physico‑chemical factors most strongly associated with enzyme activities.

Results showed that soil responses to agricultural management were not uniform across sites. In some cases, the use of cover crops enhanced beneficial soil properties such as nutrient availability, whereas in others it produced negative effects, including increased bulk density. Multiple linear regression analyses indicated that enzyme activities were strongly correlated with nutrient availability, particularly soil organic carbon, available ammonium, and available phosphorus. Texture‑related parameters exerted either positive or negative effects depending on the specific enzyme. Aboveground biomass was identified as an important factor influencing arylsulfatase activity in tilled soils, while root biomass played a key role in dehydrogenase activity in soils managed with cover crops.

These findings suggest that, at least in the conditions studied, the impact of vegetation cover on soil improvement cannot be considered generalizable but is instead site‑dependent.

ACKNOWLEDGEMENTS

This work was supported by the European Joint Programme for SOIL (EJP SOIL), funded by the EU Horizon 2020 Programme (Grant Agreement No. 862695), within the SANCHOTHIRST project. Javier González-Canales contract is financially supported under grant PRE2021-097966, funded by MCIN/AEI/ 10.13039/501100011033 and by ESF Investing in your future.