Soil Microbial Interactions with Agricultural Plants in Depleted Urban Soils Amended with Various Organic Fertilizer Treatments.

Urban farmers face an extreme challenge in remediating abused and depleted soils. It often takes years for any food to be produced and only after extreme soil amendment practices. Our study sought a way for urban farmers to amend their soils quickly and effectively grow food in the first year of production. A polyculture of sunflowers, pole beans, and zucchini squash were grown in nine different treatments with each replicated ten times. The original soil was extremely sandy with no functional organic matter. Worm castings were used as a main effect, given their ability to immediately impact and alter the soil microbial community while introducing other nutrients. Bokashi tea, fish hydrolysate, biochar, and an experimental organic fertilizer called Grow Juice 2™ were also applied, both by themselves, and in combination with the worm castings. Worm castings alone and in combination with bokashi tea and fish hydrolysate significantly increased microbial functional and taxonomic diversity, microbial biomass carbon, soil organic matter carbon, water fraction, plant biomass, and carbon dioxide flux rate. Worm castings in combination with biochar resulted in significantly greater results in all of the aforementioned variables and was the only treatment to result in any zucchini fruit production, sunflowers and beans suffered significant losses due to deer browsing. All treatments without wormcastings showed no significant difference from the control treatment in all variables measured. These results indicate that wormcastings alone, and to an even greater extent when coupled with biohcar, significantly affected the soil microbial population and physical properties of the soil, which in turn, increased the plant growth. These effects have been well documented and further establish the importance of a diverse microbial soil population in any agricultural system. New, and even seasoned, urban farmers could find immense benefit in amending their soils with worm castings and biochar.