Influence of alternative soil amendments on mycorrhizal fungi and cowpea production

Authors: COBB, ADAM - Oklahoma State University; WILSON, GAIL - Oklahoma State University; GOAD, CARLA - Oklahoma State University; Grusak, Michael

Submitted to: Heliyon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2018
Publication Date: 7/20/2018
Citation: Cobb, A.B., Wilson, G.W., Goad, C.L., Grusak, M.A. 2018. Influence of alternative soil amendments on mycorrhizal fungi and cowpea production. Heliyon. https://doi.org/10.1016/j.heliyon.2018.e00704.
DOI: https://doi.org/10.1016/j.heliyon.2018.e00704

Interpretive Summary: Cowpea and other pulse crops require adequate and available soil nutrients to grow optimally and to produce high quality seeds. Efforts to manipulate soil composition and health can improve mineral nutrient availability to growing crops. In this study, we tested the addition of two soil amendments on cowpea production. We added worm compost or a processed carbon source (known as biochar) to soil, or both treatments together, in combination with different fertilizer treatments. We measured their effect on the abundance of soil fungi on roots, plant yield, and seed nutritional quality. We found that the worm compost plus biochar could be used with reduced rates of fertilizer application to achieve high yields and nutrient-dense cowpea seeds. These results suggest alternative agronomic practices that farmers can use to enhance soil quality, reduce input costs for cowpea production, and improve agricultural sustainability.

Technical Abstract: 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.