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Potential carbon and nitrogen mineralization in soils from a perennial forage production system amended with class B biosolids

Jin, Virginia L., Johnson, Mari-Vaughn V., Haney, Richard L., Arnold, Jeffrey G.
Agriculture, ecosystems & environment 2011 v.141 no.3-4 pp. 461
biosolids, carbon, carbon dioxide, fertilizer rates, forage production, mineralization, nitrate nitrogen, nitrogen, nutrient transport, production technology, soil, soil organic carbon
The effects of biosolids application rate and history on soil potential C and N mineralization were measured over a 112-day laboratory incubation. Soils were collected from a large-scale biosolids recycling operation that surface-applies anaerobically digested Class B biosolids for commercial forage production. Five treatments were evaluated: unamended control; 22Mgdrybiosolidsha⁻¹y⁻¹ applied for 25 years; 22, 45, and 67Mgha⁻¹y⁻¹ applied for 8 years. Biosolids additions enhanced total soil organic C by 32–92% and total N by 30–157% compared to unamended soils. Total N increased with application rate and was dominated by nitrate-N. Potential C mineralization (cumulative CO₂ produced) was 11–62% greater in amended soils compared to controls and highest at 67Mgha⁻¹y⁻¹. Net N mineralization and immobilization were highest early in the incubation for 45 and 67Mgha⁻¹y⁻¹ treatments. No significant differences in potential C and N mineralization between controls and soils amended at the lowest rate for 8 or 25 years suggests that biosolids applications at 22Mgha⁻¹y⁻¹ are sustainable over the long-term. Higher potential N mineralization rates and soil nitrate concentrations under higher application rates may increase the risk of off-site nutrient transport and requires further evaluation.