Most of the olive orchards in Northeastern Portugal are on steep slopes. Tillage is the usual soil management system for these orchards the combination of both these factors increases greatly the risk of soil erosion. To protect the soil, alternative weed-control systems, such as the use of post-emergence herbicides, must be implemented. As collateral effects, the weed-control systems may influence several
aspects of soil fertility and crop nutrition, including P availability. The bioavailability of in these soils frequently low, mainly if they are acid, due to phenomena insolubility. Consequently, regular application of P fertilizers is needed to promote the growth of crops (Arrobas and Coutinho, 2002). The ‘ii of this work is to study how the different soil surface management systems can affect the soil P dynamic in a rainfed olive orchard.
