Cation Exchange and Reducing Capacities as Criteria for Compost Quality

Cation exchange capacity (CEC) and reducing capacity (RC) in relation to compost stability and quality were studied. The results show that grape prunings, husks and seeds compost and vine branches compost were nearly stabilized after 120 days of composting. The CEC of the vine branches compost (23.1–66.5 cmol kg−1) and the grape prunings, husks and seeds compost (98.3–138.7 cmol kg−1) was high during that period. Their reduction power was low and the quality of these composts was very good. The CEC of sawdust composts was noticeably lower (2.9–14.4 cmol kg−1) after 180 days. After 360 days of composting they were nearly stabilized and the CEC drastically increased (80.9–83.8 cmol kg−1). The reduction power of the sawdust composts was high during one full year and they could be applied to the soil with precautions within this period. Next to the cation exchange capacity the reducing capacity appeared to be a reliable and important criterion for compost quality, especially with respect to the protection of soils from intensive reduction processes. Significant correlations among CEC, RC and CO2 production were observed during the first 4 months of composting. However, the results can be applied only under defined conditions.