As our understanding of the microbiome’s importance to agriculture improves, questions surrounding effective microorganism inoculants as crop treatments continue to arise. These products purportedly increase nutrient bioavailability and enhance plant growth. However, these vary in contents by producer and can be costly, especially given the inconsistent results on their efficacy. Local effective microorganisms (LEM) are alternative formulations produced with local forest litter and carbon sources that can be produced at scale on-site by farmers using local ingredients. LEM application has previously been shown to alter the dynamics of nitrogen availability and soil microbial populations when added to soil amendments, and may influence crop quality and microbial community resilience. However, long-term research on its relevance to organic vegetable rotations is still in its early stages. This project sought to determine the impacts of LEM application on the yield and quality of organic vegetable crops, and to compare soil nitrogen dynamics of these systems to a controlled laboratory incubation. In the field component, a vegetable rotation consisting of kale, carrot, or crimson clover (spring) and green beans (fall) was grown at three different organic farms in the Georgia Piedmont region for two years, and received either a control, low, or high LEM application rate twice per year. Soil samples were taken periodically for inorganic nitrogen, and at harvest total and marketable yields were taken. Subsamples of each harvested plot were juiced and analyzed for sugar content via %Brix. The laboratory incubation was performed on samples obtained from each plot from the field study, which were incubated for 120 days at a standard water content. Each microcosm received either no treatment or an LEM treatment analogous to its respective field plot at time zero. Sulfuric acid traps were used to measure ammonia volatilization, and samples were periodically taken from each microcosm to be analyzed for inorganic nitrogen and pH. At Day 28 of incubation, the average total inorganic nitrogen across treatments was 5.68 ppm. At the end of incubation, the average pH across all treatments was 5.97. The average %Brix for the beans across all locations was 3.5; plants that received high LEM showed higher Brix in plots where crimson clover was the winter crop in two of the three locations, and in plots where kale was the winter crop in one of the locations. These results indicate that LEM may influence produce quality metrics in some common vegetable crops.
