The legume choice in a relay intercropping system with durum wheat determines the economic viability of this IWM strategy in a Mediterranean low-input cropping system

19^th European Weed Research Society Conference, Athens, Greece, 20-23 June 2022

This work raises the questions, is the relay intercropping of subsidiary legumes with durum wheat a sustainable intercropping practice from an economic point of view? Which subsidiary legume among Medicago sativa, Trifolium repens, Hedysarum coronarium, Medicago lupulina, Trifolium incarnatum, Trifolium resupinatum; Trifolium subterraneum, and Medicago polymorpha maximize the profitability of relay intecropping in a low-input cereal based Mediterranean cropping system? Therefore, an assessment was performed to evaluate the economic sustainability of several subsidiary legumes for relay intercropping with durum wheat, taking into account the impact of legumes on the co-cultivated wheat and to the subsequent forage sorghum. A 2-years plot experiment was carried out in Pisa (Tuscany) in a complete randomized block design with 4 replications. Legumes were sown in the already established wheat in late winter. After the wheat harvest legumes were maintained in the field until the subsequent spring and incorporated into the soil by plowing. Forage sorghum was sown for the evaluation of the residual effects of each legume on the subsequent crop. Gross Income (GI) was calculated for wheat and sorghum as the difference between the Gross Production Value (GPV) and the total production costs (C). The overall economic impact of relay intercropping in a wheat-sorghum rotation was estimated by the calculation of the cumulative GI. Results of this study reveal that relay intercropping reduces profitability of the co-cultivated durum wheat because the productive advantages do not cover the additional costs due to the inter-sowing operations. After the wheat harvest the presence of legumes in the field ensure a good weed control and potentially allows to reduce tillage and herbicides application with an estimated save of 195 €/ha compared to the conventional management. The gross income of sorghum preceded by these legumes is higher compared to the control and it can be up to 955 €/ha. According to the legume choice, relay intercropping of legumes demonstrated to satisfy nutritional requirements for the subsequent sorghum and allows to reduce the input costs up to 253 €/ha. H. coronarium and T. repens were identified as the best performing legumes from an economic point of view. For these legumes the costs due to the relay intercropping were balanced by the ecosystem services that they provide at crop rotation level.