The health of humans and ecosystems are closely interlinked, therefore fostering healthy soils may aid in addressing micronutrient deficiencies. Healthy soils are active with diverse microbial and mesofauna communities that carry out soil processes that are essential for crop growth and development. A greenhouse experiment was conducted to investigate the effect of soil mesofauna on micronutrient content in vegetable crops and determine if plant root structure or shifts in soil microbial community composition (relative pathogen abundance) impact these affects. Crop species (snap beans and beets), Collembola (Isotomiella minor) abundance (none, low, or high), and microbial community composition (native community and pathogen-dense community) treatments were imposed and replicated five times. The soil treatments were prepared by sterilizing soil and inoculating the soil with the two different microbial communities. The inoculated soil was placed in pots and one cup of compost was mixed into the top 5 cm. Snap beans and beets were planted at a depth of 2.5 cm and 0.25 cm, respectively. The Collembola treatments (none, 100 Collembola, 200 Collembola) were then added to the appropriate pots. Weekly checks were conducted to monitor plant health and growth. Once each crop reached maturity (approximately 60 days), a destructive harvest was conducted. Crop biomass and marketable yield fresh weights were recorded and I. minor abundance was verified at the harvest. Crop biomass samples were frozen for later analysis of minerals relevant to human health including essential nutrients (e.g., calcium, sodium, magnesium, potassium, iron, and zinc) and heavy metals (e.g., lead, cadmium, and arsenic). Minerals were extracted via microwave digestion in nitric acid and quantified via ICP-MS. We hypothesized that the concentration of micronutrients in the vegetables will increase as I. minor abundance increases, and that the I. minor will have a greater effect on the snap bean compared to the beets due to the greater root surface area. Additionally, we conjectured that a pathogen-dense microbial community will diminish the effects of I. minor on micronutrient uptake, since greater pathogen presence would likely decrease their direct interactions with crop roots. We found that the addition of I. minor enhanced crop growth regardless of soil microbial community composition. The beets were more sensitive to changes in soil microbial community composition compared to the snap beans. Our findings illustrate the importance of healthy soil biological communities for quality vegetable production.
