Forage sorghum-legumes intercropping: effect on growth, yields, nutritional quality and economic returns

ABSTRACT Cereal-legumes intercropping is among the most economical and effective agronomic strategies to boost forage biomass production, nutritional quality and monetary returns. This review synthesizes the research findings on how intercropping affects productivity, quality, competitiveness and economic viability of sorghum-legumes mixed, row and strip intercropping systems under varied pedo-climatic conditions. Though component crops show yield reductions in row (additive and row-replacement series), mixed (seed blended crops) and strip intercropping systems, in general overall productivity per unit land area increases to a great extent. The significantly higher resource capturing with better utilization efficacy by intercrops in temporal and spatial dimensions helps explain their greater productivity. In addition, forage intercrops result in improved nutritional quality as legumes contain protein in double quantity than cereals. Cereal-legumes intercropping systems yield higher quantities of lush green forage with improved quality traits, which ultimately increase monetary benefits. Furthermore, legumes inclusion as an intercrop with cereals has the potential to serve as a nitrogen-saving strategy due to the biological nitrogen fixation (BNF) process. Moreover, cereal-legume intercropping systems are effective in reducing weed infestations and soil erosion by providing extended soil cover, as well as in increasing water use efficiency and improving soil fertility. However, despite a significant increase in overall productivity, component crops suffer yield losses in intercropping systems owing to competition for the finite divisible pool of growth resources. Thus, there is a dire need to optimize spatial and temporal arrangements in sorghum-legumes intercropping systems to achieve maximum productivity and economic returns.

摘要：禾本科-豆科间作（cereal-legumes intercropping）是提升饲草生物量产量、营养品质与经济效益最具经济性与实效性的农艺策略之一。本综述系统梳理相关研究成果，探讨了不同土壤-气候条件下，间作如何影响高粱-豆科混合种植、行间作与条带间作系统的产量、品质、竞争力及经济可行性。尽管行间作（含添加型与行替换型配置）、混播间作（即种子混合播种的作物体系）以及条带间作系统中的间作组分作物均出现产量降低，但总体而言单位土地面积的总产量仍得到大幅提升。间作体系在时空维度上具备更强的资源捕获能力与更高的资源利用效率，这正是其生产力更高的核心原因。此外，饲草间作系统的营养品质得以改善，因豆科作物的蛋白质含量为禾本科作物的两倍。禾本科-豆科间作系统可产出更多鲜嫩青绿饲草，且品质性状更优，最终提升经济收益。进一步而言，将豆科作物与禾本科作物间作，借助生物固氮（biological nitrogen fixation, BNF）过程，可作为有效的节氮策略。不仅如此，禾本科-豆科间作系统通过延长土壤覆盖时长，可有效抑制杂草为害与土壤侵蚀，同时提升水分利用效率与土壤肥力。然而，尽管整体生产力显著提升，但间作系统中的组分作物仍会因有限且可分配的生长资源竞争而出现产量损失。因此，亟需优化高粱-豆科间作系统的时空配置模式，以实现最高的生产力与经济回报。