Abstract
The effects of pH in two different composts were studied. Yamagata compost was made under aerobic conditions, while Shimoduma compost was under semi-aerobic conditions. The change in pH of Yamagata compost was very limited, 7.38–8.97, and it started to increase only after 40-th d of composting. The pH increase from 40 to 70 d coincided with an increase in ammonium content, while a decrease after 70 d was probably as a result of nitrification. The concentration of organic acids (formic, acetic, propionic, iso-butyric and iso-valeric) produced in the first 14 d was high and after that, acetic, propionic and iso-valeric acids decreased quickly. In the Shimoduma compost, however, the range of pH change was wider (3.95–6.65) and increased almost linearly. The quantity of organic acids (citric, lactic, formic and acetic acid) produced depended on the periodic manual stirring. Immediately after stirring the amount of acids decreased, but it increased during the period without stirring.
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