Carbon Fractionation of Biosolids Amended Soils - Impact on Carbon and Nitrogen Storage in Soils.

Anaerobically digested and dewatered biosolids can be an effective source of nutrients in a cropping system. In a long-term study at Waterville, WA, biosolids have been used as a crop nutrient source on winter wheat-fallow every four years since 1994 (Cogger et al., 2014). Carbon fraction analysis funded by USDA AFRI REACCH has recently been conducted on historical soil samples from this site, and shows that acid resistant and light fraction carbon pools in the soil increase with applications of biosolids, while the heavy soluble C fraction has not changed over time. The trend is for soil C levels to increase as biosolid C is added; about 18% of the added carbon is stored in the acid resistant fraction and 34% in light fraction. Due to augmentation of these C fractions, total soil C increases by around 50% of what is applied. In contrast, total soil nitrogen only increased by 22% of N applied due to crop uptake and grain removal from the system. This research demonstrates that application of biosolids to wheat increases stable C sequestration above and beyond what wheat straw alone returns.