Assessment of the reliability of a commercial maturity test kit for composted manures. Compost Science and Utilization 11:125–143

Stability significantly affects the potential for beneficial utilization of composts but is dif-ficult to measure by farmers and compost producers. A simple four hour test (the Solvi-ta ® maturity test) that measures CO2 evolution and ammonia emission from compost samples was compared to a traditional three-day, 25ºC, CO2 evolution rate procedure and to measurements of ammoniacal nitrogen concentrations in manure composts to assess the reliability of this test. Three composts — 1) Dairy manure amended with wheat straw, 2) The same dairy manure but amended with sawdust and 3) Swine ma-nure amended with sawdust and ground wood pallets — were composted in windrows for 120 days. Samples were removed weekly to biweekly. CO2 evolution rates of the three composts decreased from initial means (n=6) of 3.41, 3.42 and 9.35 to 0.63, 0.76 and 0.31 mg CO2-C g-1 VS day-1, for the dairy manure-straw, dairy manure-sawdust, hog manure composts, respectively. The corresponding mean Solvita CO2 test values for these composts increased from 3.4, 3.0 and 3.2 to 6.8, 6.5 and 7.0, respectively. Correla-tion analysis between CO2 evolution rates and Solvita CO2 test values gave linear cor-relation coefficients (r) of-0.82,-0.78, and-0.87 for the straw-amended dairy manure, th