Linkages between farming practices, crop yield and weed communities in rainfed Mediterranean agroecosystems

For rainfed cropping systems in semiarid regions to be sustainable, they should provide multiple agroecosystem services simultaneously while accounting for the environmental constraints inherent to these areas. Achieving this may require a reevaluation of the main farming practices, including the choice of tillage system and fertilization rates. In this study, we present, for the first time, an integrative evaluation of these practices that considers crop performance, weed management, and the conservation of weed community diversity. Over four crop seasons in a cereal–legume rotation, we compared the effect of three tillage systems (conventional, minimum, and no-till) and two fertilization rates (full NPK vs. 50% reduction) on crop yield, weed abundance, and weed diversity -both species diversity (inverse Simpson index) and functional diversity (mean pairwise distance of six traits; MPD)- using Structural Equation Modelling. The effects of fertilization and of the choice of tillage system were more pronounced on cereal than on legume crops. In cereals, reduced fertilization rates and lower tillage intensity increased yields, consistent with previous studies on crop performance under water-limited conditions. Weed abundance and trait composition were more responsive to tillage than to fertilization: reducing tillage increased abundance and the diversity of resource acquisition traits but decreased species diversity and the diversity of regenerative strategies. These findings show the potential of reducing fertilization rates without compromising crop yields, enhancing farmer’s profitability and sustainability. Further, our results reveal a disconnection between tillage effects on crop yield and on weed management and diversity, each of which is better achieved by no-till or by conventional systems. Minimum tillage could be a ready-to-use strategy to combine both goals, but we acknowledge that a research and technical gap exists to maximize crop yield, weed management and soil structure maintenance in these systems.