Abstract

Soil fertility improvement is one of the urgent issues in Malawi. Since composting by locally available materials is needed for this purpose, the composts were prepared from maize stalk and cattle dung by using three common methods in Malawi. The composts had high alkalinity and relatively high NO₃^- and K contents. N% of composts was determined from the composition of maize stalk and cattle dung, and is expressed by the equation N% = 0.55 - 0.01 x % maize stalk + 0.03 x % cattle dung (r² = 0.37). Maize stalk is rich in acid digestion fiber (ADF) (39.3%), which accounts for its slow decomposition, whereas cattle dung is mainly composed of ash (73.5%), which is rapidly degradable inorganic material. The temperature change during fermentation was indicative of compost maturity. Mature composts were exposed to fermentation temperatures exceeding 50°C for a longer period, and had lower pH and higher EC and available N content. The germination rate of rape seeds measured with compost extract was compatible with the absorption value at 465 nm, indicating that these methods are simple and practical for testing compost maturity. The EC difference between wet and dry composts was also useful for identifying the end of fermentation. Low C/N (23) compost demonstrated rapid fermentation relative to high C/N (40, 60) composts, indicating the importance of adjusting C/N in compost fermentation.

Key words: Compost, fermentation, acid digestion fiber, maturity.