Establishing new legume-based farming systems in Northeast Thailand using drought-tolerance traits of wild legume and rhizobia populations

Nitrogen (N) is required for plant growth in large quantities, yet it is typically deficient in tropical soils. Unlike other elements that must be replenished by mineral fertilisers, plant-usable N can be supplied by legumes that perform Biological N2-fixation (BNF) in association with rhizobia bacteria. This is particularly important in Northeast Thailand where most smallholding farmers cannot afford sufficient fertiliser inputs. There, the benefits of BNF remain low, however, as the vast array of native legumes are underused despite their adaptiveness to this region’s distinctively prolonged droughts. Factors limiting their adoption are lack of integration guidelines and inadequate availability of effective rhizobia inoculants. To formulate new legume-based systems, this research aims to exploit the drought-tolerant traits of wild legumes growing in Northeast Thailand. Diverting from a ‘top-down’ approach, farmers’ objectives and farming typologies will be identified by short-structured interviews to guide the selection of legume species. To identify superior symbionts, the rhizobia community will be discerned by whole nodule amplicon sequencing of the 16S rRNA, gyrB and nifH genes. Isolate effectiveness will be assessed by measuring host parameters associated with N2-fixation efficiency. In addition, in-field quantification of BNF and analysis of the N dynamics will be conducted to evaluate the proposed legume-based systems.