Abstract
Organic amendments are the necessities of sustainable usage of crop land. However, it is not established yet how to evaluate their quality. In this report, the authors evaluated the quality of 11 organic amendments which were sold at local markets around Kyoto City based on their CO_2 evolution rates, chemical analyses, and seedling tests using Komatsuna (Brassica campestris L.). The amendments included composts made of yard trimmings, animal wastes, and food-industry sludge, together with dried chicken manure and rapeseed cake. Chemical analysis (pH, EC and total nitrogen content) indicated that all the composts accorded with the recommended quality standard. Evolution rate of CO_2 for all the materials were recorded up to 20 d. The rates were lower for the compost (0.13 to 1.7mg C evolved per g dry matter per day), and the rates were kept constant up to 20 d. which indicates that those materials were well fermented. In the plant test, an aliquot of the amendment equivalent to 200 mg total nitrogen was applied to 1kg sandy soil in a pot. Under the current dressing rate, none of the amendments inhibited germination, but the plant growth differed from material to material, maybe because of the different amounts of available nitrogen in them. It is concluded that a compost is stable if the CO_2 evolution rate is below 2mg C evolved per g dry matter per day, and that this criterion is applicable to all composts irrespective of the starting materials.
