Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/7/2005
Publication Date: 11/7/2005
Citation: Griffin, T.S., Hutchinson, M. 2005. Changes in C and N mineralization with compost maturity. American Society of Agronomy Abstracts. ON CD Interpretive Summary:
Technical Abstract: Improved predictive relationships between compost maturity and nitrogen (N) availability would be helpful in establishing the balance between soil properties and nutrient availability. We collected eleven separate compost samples from a single windrow over a 100 d period, beginning when the compost met minimal National Organic Standards. Compost maturity was assessed using both standard analyses (total C and N, mineral N, total volatile solids) and other methods (CO2 evolution, commercial maturity kits, and neutral and acid detergent fiber). Compost N transformations were evaluated during an aerobic incubation in a sandy loam soil, sampled at 0, 7, 14, 21, 28, 56, 84, 112, and 130 after each compost was applied at 200 mg total N kg-1 soil. Net mineralization of compost N was assessed for each compost. Compost C mineralization was assessed by measuring CO2 released from each compost+soil mixture in the 24 hr period prior to each soil N sampling. Regression analysis was used to evaluate the relationship between compost maturity parameters, the rate and extent of net N mineralization, and C mineralization. Commonly used maturity parameters like total C, total N, and C:N ratio were poorly correlated with the rate and extent of mineralization. The N mineralization rate during the first 70 d of incubation was strongly correlated (r= -0.70 to -0.80) to compost Maturity Index and to compost fiber concentration. Trends in C mineralization were similar. There were few differences between composts after 70 d. Methods of characterizing compost maturity that more realistically reflect the composting process are better predictors of N release after incorporation into soil.