There is a growing realisation that the use of degraded habitats for agricultural production is becoming an increasingly practical and economically viable alternative target, or state, to clearing pristine environments, which are optimally managed and conserved for the protection of biodiversity and ecosystem services. Given their synergies in terms of availability of labour, machinery, and the need for food and animal feed, the two major industries of mining and agriculture should collaborate. Although there are many advantages for agricultural production following mining, substrates often have abiotic and biotic challenges for plant growth, including poor fertility, heavy metals, and a lack of beneficial soil microbes. A nutrient trial was established to investigate methods of increasing plant biomass and health in a post-phosphate mining environment using a well-known legume as a model species, Lablab purpureus L. Sweet.
We found that the addition of potassium (K) significantly increased plant biomass, enhanced root growth, and enhanced mycorrhizal fungal colonisation rates. Potassium amendment was also associated with significantly lower heavy metal levels in plant material. We hypothesise that heavy metals were either diluted in larger biomass or healthy, non K-limited plants can select against heavy metal uptake. Clearly, K is the critical nutrient for legumes in post-phosphate mine sites for enhancing biomass and health. These results have global ramifications for successful transitioning from mining to agriculture (in terms of food security, food safety and sustainable employment for stakeholders, and information for land-use policy makers), but also for restoration of native vegetation in ex-mined sites.