BLOOM BIOSOLIDS: WHAT IS THEIR MICROBIAL COMMUNITY AND HOW DO THEY AFFECT SOIL AND PLANT HEALTH?

Abstract

Biosolids are rich in nutrients and organic matter, and are known to improve and maintain productive soils and stimulate plant growth. D.C. Water’s new Class A biosolids product, Bloom, was evaluated for its impact on plant and soil health. Using molecular tools, Bloom was examined for the presence of functional genes that would indicate the presence of microbes capable of improving plant growth (i.e.nitrifiers, N- fixers). Using greenhouse and laboratory experiments, we determined Bloom’s effect on plant growth, carbon and nitrogen cycling. Bloom has both nitrifying and N-fixing microbes, but their gene numbers vary depending on the stage of production. We show that plants, such as cucumber and tomato, grown in soil amended with Bloom produce more leaves and stems and have higher aboveground biomass, and soybeans produced more bean pods. Lastly, we found that N-mineralization is higher in soil amended with Bloom, even after one growing season, providing increased nutrients.