Mathias Christina1,2, Julien Chetty3, Pauline Viaud2,4, Thomas Lizekne3, Léa Chevalier1,2,3,5,6, Sandrine Auzoux2,4, Antoine Versini5,6, Krishna Naudin1,2 and Alizé Mansuy3
1CIRAD, UPR AIDA, F-34398 Montpellier, France; mathias.christina@cirad.fr
2AIDA, Univ Montpellier, CIRAD, Montpellier, France
3eRcane, F‑97494 Sainte‑Clotilde, Réunion, France
4CIRAD, UPR AIDA, 97743 Saint-Denis Cedex 9, La Réunion, France
5CIRAD, UPR78, Recyclage et risque, 97400 Saint-Denis, La Réunion, France
6Recyclage et Risque, Univ Montpellier, CIRAD, Montpellier, France
Intercropping can enhance the sustainability of sugarcane cropping systems and provide ecosystem services, along with improving crop productivity and decreasing environmental impacts. This practice, involving the simultaneous cultivation of multiple crops, fosters diverse plant communities and increases complementary interactions. In Réunion, intercropping has been studied for over 15 years, and the results of 10 experimental trials are presented based on published and additional results. Companion crops in sugarcane inter-rows reduced weed growth and herbicide use, with weed control efficiency varying by weed communities and climate. The introduction of legumes as an intercrop has increased nitrogen fixation when tracked using 15N labeling. However, significant nitrogen volatilization due to legume-sugarcane straw interaction revealed the need for improved crop management. Soil chemical fertility remained unchanged after 7 years, but soil physical fertility showed improvement, notably in infiltration. Companion crops influenced sugarcane development, affecting tillering and root exploration and limiting water and nutrient access. Compared to conventional chemical weeding, yield decreased by an average of 6% in Réunion and 3% worldwide in a meta-analysis. Crop management adaptations must be explored (particularly sowing and harvesting date) to find the appropriate compromise between sugarcane yield response and weed control efficiency. Economic assessment of intercropping systems compared to monocropping showed reduced intercropping profitability and increased labor hour rates in the economic conditions of Réunion. Nonetheless, the change in cost is mainly linked to the companion crop sowing method and can be lowered using mechanical sowing methods. Finally, the limits and interests of this practice from the farmer’s view were also explored as part of the IntercropValues project. Despite the solid interest of farmers in this practice, several limits must be overcome (seed availability, value chain for the companion crop, or agroecological sugarcane) for this practice to spread.