Soil physicochemical changes under sandwich mounds technique in a rainfed semi-arid Tunisian agroforestry system

The sandwich mound technique is a traditional agricultural method, particularly favored in permaculture, that harnesses soil biological activity and high organic matter input to promote sustainable crop production. A preliminary 6-month trial was conducted in a semi-arid area of Tunisia, at the Higher School of Agriculture of Mograne, to assess the effects of the Sandwich Mound (SM) technique, implemented in a rainfed agroforestry system consisting of an olive orchard enclosed by cypress and acacia tree windbreaks, on selected soil physicochemical properties. The results showed that the SM practice within this cropping system had a significant effect on soil water retention and storage, particularly in the 20–80 cm soil horizons, with an average increase in moisture content of 1.2% compared to the control without mounds. This technique improved soil organic matter content by 40% and electrical conductivity. However, it significantly reduced soil pH compared to the control. Moreover, it enhanced soil permeability, thereby increasing water retention in adjacent zones. This effect is further enhanced by the capture of additional runoff water, collected by the terrace structure elevated 20 cm on two sides of the mound. These findings suggest that integrating the SM technique into rainfed agroforestry systems effectively improves soil properties and water retention. This supports better crop adaptation to semi-arid climates even over a short period. This approach offers a promising pathway toward more sustainable and resilient agriculture in regions vulnerable to climate change and water scarcity such as Tunisia.