Ground Management Through Grazing in Rainfed Olive Orchards Provides High Olive Yields and Has Other Potential Benefits for Both the Soil and the Farmer

Abstract

Soil management in orchards can have several economic and environmental implications. In this study, three different soil management systems were compared in a dry-farmed olive grove: conventional tillage (tillage), glyphosate-based herbicide (herbicide) and sheep grazing. The experiment lasted eleven years (2011–2022) and was carried out after a previous trial conducted on the same plot with the same treatments and duration (2001–2011). However, in the earlier trial, the herbicide and sheep grazing treatments switched positions in the plot, while the tillage treatment remained in its original place. The average total accumulated olive yields between 2011 and 2022 were 225.1, 230.9, and 245.0 kg tree−1 for the sheep grazing, tillage, and herbicide treatments, respectively. However, no significant differences were observed between the treatments. The levels of total organic carbon in the soil, measured in samples collected in the last year of the study, were 41.3, 33.7, and 37.3 g kg−1, respectively, for the same treatments. These findings indicated that the tillage treatment exhibited lower soil organic matter content and reduced bioavailability of some nutrients, which raises concerns about its sustainability. On the contrary, employing sheep grazing with an appropriate stocking rate, effectively controlling vegetation in the spring, ensured favourable soil properties and olive yields comparable to the other treatments. Moreover, the sheep grazing approach provides supplementary advantages to the farmer, including revenue from the sale of animal products and the opportunity to transition to organic farming systems, which better align with the preferences of contemporary societies.