Agronomic performance of soybean and sorghum in a short rotation poplar coppice alley-cropping system under Mediterranean conditions

The transition from conventional arable towards silvoarable systems can increase the delivery of ecosystem services. Nevertheless, the assessment of crop yield under agroforestry condition is crucial to evaluate of the reliability of these systems and to increase the knowledge base needed to support their design. Although the feasibility of poplar short rotation coppice (SRC) silvoarable alley-cropping systems has been widely investigated, few studies have addressed the agronomic response of crops intercropped with poplar SRC in narrow alleys, especially in Mediterranean environments. Thus, this paper treats the effects of SRC poplar rows on soybean and sorghum productivity in a 2-year rotation implemented in an alley-cropping system. A field experiment was carried out in 2018 and 2019 with the objective of measuring and evaluating effects of light availability variation, as affected by the growing rate of 2-year coppice cycle poplar SRC rows, and the soil characteristics on soybean-sorghum and sorghum–soybean rotations. Above-ground biomass, grain yield and crops residue showed a significant reduction in the tree–crop interface up to 74% and sorghum proved to be less tolerant to light reduction compared to soybean. Our results demonstrated that light is the most important factor for sorghum cultivation, despite grain yield was also influenced by the soil characteristics such as pH, while soybean is affected also by soil moisture and water retention capacity. The design of crop rotation in an SRC-based agroforestry system needs to consider the different agronomic performance of different crops and the harvest cycle of tree rows.