EcoInt

Limited access to land and ongoing desertification threaten the sustainability of organic rooibos tea production in South Africa. This project explores the potential of microbial root symbioses to assist rooibos nutrition and growth. By uncovering the large diversity of beneficial microbes present in rooibos roots, low-cost management practices to sustain rural livelihoods can be identified.

Ecological knowledge is a prerequisite for managing natural soil microbiological resources. Yet, despite obvious potential, techniques to actively reap benefits from indigenous microbial communities for agricultural plant production are virtually non-existent. Here, we propose evaluating plant- and farming system-level management techniques to overcome yield declines in plantation cultivation of rooibos (Aspalathus linearis), a leguminous tea bush, endemic to the unique fynbos vegetation of the Western and Northern Cape provinces of South Africa. As an early microsuccessional plant, rooibos suffers in cultivation from mineral nutritional imbalances, including phosphorus (P) toxicity, and pathogen accumulation, when grown for prolonged times on the same land. To make the production of this popular cash crop environmentally sustainable, we propose evaluating simple soil management measures, which shall mimic the growth conditions in the crop’s natural habitat. In common garden-type nurseries, the effects of dung addition and microbial augmentation on plant growth, mineral nutrition, and health will be tested in a cross-factorial manner. The indigenous microbial communities of soil from semi-natural grazing grounds are expected to be suitable to rapidly associate roots of rooibos seedlings with rhizobia, arbuscular mycorrhizal fungi and other microbes to make them efficient in acquiring nitrogen and phosphorus and protected against detrimental diseases caused by oomycetes, impairing proper root functioning. The nutritional statuses and microbial community compositions and structures of plants from wild natural populations and new and old plantations will serve as references to evaluate the success of our combined soil management. Paired state-of-the art molecular microbial community and plant nutritional analyses shall provide the necessary mechanistic insights. Farmers’ awareness about soil microbial services will be raised by developing a new, illustrated extension leaflet, based on the understanding of the farming system, obtained through observations, experiments, and interviews and discussions with farmers.