A considerable growth in the maize (Zea mays L.) sector in Southeast Asia has resulted in a rapid expansion and intensification of maize monoculture on sloping uplands. This practice entailed the heavy use of fertilisers, leading to environmental degradation and farmers' indebtedness. Intercropping of legumes with maize could complement or replace fertiliser inputs; however legume adoption by smallholder maize farmers remains low. This study investigates the constraints and potentials to integrate legumes in maize‐based cropping systems in such environments. A comparative study between maize monocropping and maize/legume relay cropping was carried out in two villages of Thailand, using surveys, participatory rural appraisal (PRA) tools and interviews. The results demonstrated that both cropping systems were equally profitable, although the maize yield in maize/legume relay cropping was lower than that in monocropping. Low selling price was the most cited reason by the non‐adopters for not introducing legumes. Selling price of legume grains, ease of harvesting, marketability and ease of growing were the four main criteria that determined the adopters' choice of legume species. Among the cultivated legumes, ricebean (Vigna umbellata L.) best fulfilled the criteria for the choice of legume species. Establishing maize/legume relay cropping as an alternative to maize monocropping under rainfed conditions can decrease risks, due to reduced expenses for farm inputs and similar economic returns. This study generated useful information for agricultural policy makers and development practitioners in identifying the barriers and facilitating factors that influence farmers' decision to adopt legumes and the conditions that shape the farmers' decision‐making environment. Copyright © 2016 John Wiley & Sons, Ltd.

Intercropping of legumes can be a strategy to improve soil fertility and enhance overall productivity while reducing dependency on external inputs in intensified cropping systems. Integration of legumes in maize-based cropping systems is promoted as an agro-ecological intensification option for input-constrained smallholders in uplands of Southeast Asia, but adoption rates in the region remain low. The overall aim of this study was to assess the suitability and trade-offs of integrating ricebean in maize-based smallholder cropping systems in upland areas of Northern Laos. We conducted a researcher-managed field trial to investigate the agronomic performance of ricebean/maize intercropping, and farmer-managed trials combined with surveys (N = 97), and focus group discussions in 10 villages to understand factors influencing farmers' decision making concerning ricebean adoption. Drought, rat infestation and crop damage by grazing livestock were identified as important constraints to the production of ricebeans. Factors facilitating adoption included improvement of soil fertility, the potentially high selling price of ricebeans and the presence of extension agents, while barriers included labour shortage, concerns about competition with maize and lack of a market outlet for the ricebean produce. We conclude that the investigated maize/ricebean intercropping system is poorly suited to the current conditions in the study area, and call for farm-based studies focusing on developing locally adapted legume intercropping systems able to perform under variable rainfall conditions. Initiatives addressing challenges related to free grazing livestock and efforts to link legume producers in remote areas to emerging markets are also needed.