Sustainable farming needs to harness the benefits of soil microbes to restore soil and produce nutritious food. As agricultural fields are depleted of soil carbon and microbial biomass, increasing fertilizer inputs are required to maintain crop yield. Mounting fertilizer costs are disproportionally hurting farmers in developing countries. Our greenhouse study investigated the effects of alternative farm inputs (compost & biochar) and arbuscular mycorrhizal (AM) fungal associations with grain sorghum and cowpea on efficiency, productivity, and nutritional quality of these important agricultural crops. These soil amendments can be produced at various scales, with potentially lower cost than commercial fertilizers. AM fungi grow in association with the roots of the vast majority of agricultural crops. In addition to directly assisting plant uptake of nutrients like phosphorus, AM fungi help build stable soil organic carbon and reduce loss of key nutrients like nitrogen from farm systems. We assessed selected cowpea and sorghum genotypes grown with 10 different input treatments (combinations of biochar, worm compost, and fertilizers) plus control with 6 reps per crop/treatment combination. Plants were harvested at 45 days post-emergence, and AM fungal root colonization and plant tissue quality were measured and analyzed with generalized linear mixed modeling in SAS.
Results/Conclusions
One input blend contained 60g worm compost and 15g of biochar (per plant) with ½ the typically recommended rate of nitrogen and phosphorus (Urea/DAP) fertilizer. For sorghum, compared to a full rate of N&P fertilizer, this blend produced equal or greater plant biomass after 45 days of growth, with equal or greater tissue quality (Protein, P, Fe, Zn), while supporting ~30% more AM fungi in the host plant’s roots. Worm compost had a significant effect on cowpea by increasing total protein and zinc content as compared to biochar treatments without worm compost; however, it had negligible impact on AM root colonization. The relative difference of mycorrhizal response between C3 and C4 plants may explain why colonization increased for sorghum but not for cowpea. These results indicate biochar and worm compost can boost belowground symbiosis with AM fungi for sorghum and crop nutrition for cowpea, resulting in increased fertilizer use efficiency. Understanding these ecological relationships is essential to ensuring global food production and nutrition security while enhancing sustainability in agricultural systems. Considering the challenge of providing food and nutrition for a growing human population, it is critical to optimize fertility inputs and the interaction of crops with mutualistic fungi.