Biological Parameters to Estimate the Effect of Biogenic Waste Composts on Plant Growth in Pot Trials

About 80 different biogenic waste composts were tested by new or modified conventional microbiological methods (oxygen-consumption, DMSO-reduction, Ehand pH-drop during anaerobic incubation, reference method: self-heating-capacity) to determine the state of maturity and the effect of composts on plant growth in pot-trials. The progress in ripening of composts could be proved well by oxygen- consumption, pH-drop and self-heating-capacity, while DMSO-reduction and Eh-drop reflected maturity only with restrictions. A satisfactory prediction of plant-growth (dry-matter-production of oats) after compost-application with the help of the biological parameters was scarcely possible, only pH-drop showed a somewhat higher correlation. It was found out, however, that the effect of compost on plants could be estimated well by making use both of the C/N-ratio and of biological parameters.