Ecological intensification in the mountains of Vietnam: Constraints to the adoption of cropping systems based on mulches and cover crops

Significant efforts are being pursued in the tropical world to develop and promote cropping systems based on mulch or cover crops (SCV, systeme de culture sous couverture vegetale, cover crop systems), in order to reduce soil erosion and improve both nutrients and water balances. However, adoption of SCV by smallholders is often limited due to the important change induced by these techniques in the management of farm's resources. The objective of this study conducted in Vietnam was to assess the feasibility of SCV that had been previously elaborated at field scale For several farm types. The method was based on the simulation of rational households optimizing the use of their resources for food-security and income. We showed that the proposed SCV were not economically attractive because of the extra labour and inputs that these techniques require during the first years of implementation. We also showed that improving the attractiveness of those SCV would require both technical adjustments, such as the use of herbicides combined with the reduction of the amount of biomass in mulches, and subsidies, More research is needed in order to better quantify the environmental services that could legitimate such subsidies. It is also necessary to better understand the causes of spatial and temporal variations of the agronomic and economic performances of the SCV and of the currently practised cropping systems. Lastly SCV should be compared to other soil conserving techniques, especially cultivation on dry terraces that is tends tending to spread out in the region.