Abstract
Multi-criteria approaches are needed to assess the agronomic, environmental, and socio-economic performance of intercropping systems. Weed pressure is a major constraint in tropical intercropping systems due to favorable climatic conditions that promote rapid weed growth, which can severely reduce crop yields and complicate management practices. However, the temporal dynamics of weed communities in these systems remain poorly understood despite their influence on long-term sustainability. This study presents the first long-term (seven-year) multi-criteria analysis of sugarcane intercropping systems in La Réunion, comparing four intercropping systems to chemical and low-weed-control systems.Weed pressure increased over the years in chemical and intercropping systems due to greater weed cover and richness. The weed community structure was affected during the first three years but later homogenized under sugarcane dominance. This pressure led to increased manual weeding in intercropping systems and more herbicide use in chemical ones, resulting in a 61% reduction in herbicide use under intercropping. After seven years, no differences were observed in soil chemical (0-30 cm) and biological fertility (0-10 cm), but physical fertility (0-20 cm) increased with the development of companion crops and weeds in the inter-row. Globally, no significant impact on sugarcane yield and sucrose content, was observed during the seven-year cycle. Nevertheless, this practice led to an increase of 77% in costs and 149% in working hours, mainly due to companion crop sowing.This study emphasizes the need to consider the dynamics of intercropping systems performances over the long term. It highlights the limits of this system for weed control in sugarcane, notably through an increase in weed pressure over time, but also ways of improving it regarding costs (particularly sowing). Further research on systems with spontaneous flora in inter-rows is suggested to reduce herbicide use with minimal yield and cost impact.