Evaluation Of Fiber Content Relative To Other Measures Of Compost Stability

Compost Science & Utilization, (2008), Vol. 16, No. 1, 6-11

M. Hutchinson (1) and T.S. Griffin (2)

(1) University of Maine Cooperative Extension, Waldoboro, Maine
(2) USDA-ARS-New England Plant Soil and Water Lab, Orono, Maine

Improved methods for assessing compost stability are needed. We collected thirteen separate compost samples from a single windrow over a 91 d period. Initial assessment of compost stability used standard analyses, including total C and N concentration, C:N ratio, and inorganic N concentration. Compost C and N lability were assessed by measuring CO2 evolution during a 24 hr period, and also using a commercially available compost evaluation kit which includes both CO2 and NH3 release to establish a Maturity Index. We also estimated slowly degradable C fractions in the composts using neutral detergent fiber (NDF) and lignin methods developed for ruminant feed analysis. The relationship between stability and each compost constituent was evaluated using simple linear regression. Some widely-used parameters, like compost C:N ratio, changed very little during compost aging. Compost CO2 evolution showed a strong linear relationship with the compost age, with a coefficient of determination (r2) of 0.82. Likewise, fiber and lignin concentration increased during compost maturation as more easily available C was used by microbes (r2 = 0.70 to 0.80). The Solvita Maturity Index was related to the compost age (r2=0.59), but fluctuated due to temporary changes in windrow conditions. These results indicate that microbial respiration and fiber analysis can be used to establish relative differences in compost stability.

Copyright 2007, The JG Press, Inc.