Influence of alternative soil amendments on mycorrhizal fungi and cowpea production

Alternative soil amendments (worm compost, pyrolyzed carbon [biochar]) and crop symbioses with arbuscular mycorrhizal (AM) fungi have the potential to reduce food production costs while promoting sustainable agriculture by improving soil quality and reducing commercial (N and P) fertilizer use. Our greenhouse studies investigated the influence of alternative soil amendments on AM fungi associated with cowpea (Vigna unguiculata [L.] Walp.) and common bean (Phaseolus vulgaris L.) by examining productivity and plant nutrition. We conducted an experiment to select a cowpea or common bean genotype based on AM fungal colonization, seed production, and seed nutritional content. We then grew the selected cowpea genotype (Resina) in low-fertility soil with 10 different soil amendments (combinations of biochar, worm compost, and/or commercial fertilizers) plus a non-amended control. There were no significant differences in AM fungal colonization of cowpea plants grow with different soil amendments. However, an amendment blend containing worm compost, biochar, and 50% of the typically recommended commercial fertilizer rate produced plants with similar aboveground biomass, protein concentration, and total protein production, with increased tissue K, P, and Zn concentration and total content, compared to plants receiving only the recommended (100%) rate of commercial fertilizer. As previous research links uptake of P and Zn with plant-mycorrhizal symbioses, our results indicate cowpea nutritional benefits may be derived from AM partnership and alternative soil amendments. These synergies between alternative soil amendments and AM fungi may help reduce farm costs while maintaining or improving crop yield and nutrition, thus increasing global food and nutrition security.