Composting dairy cattle feces at Indonesian small-scale dairy farmsa : results of a composting trial in Lembang Sub-District, West Java

The aim of this study was to evaluate effects of composting different ratios of fresh dairy cow feces and amendment material on the composition and the cost price of compost. To this end, mass balance, nutrients losses and the costs of composting were analysed in two composting trials with different ratios of cattle feces to dry amendment (‘postal’, i.e. broiler manure mixed with bedding material) in a practical farm and experimental farm in Lembang Sub-District, West Java, Indonesia. Results showed that composting reduced the weight of input materials and increased the dry matter content, thereby increasing the concentration of nutrients (total nitrogen (N) and phosphate (P)) in the final compost product compared to the initial mixture. Much N was lost during composting, particularly mineral N. Extending the composting period to eight weeks further increased the DM content and resulted in a more stable compost. Using more amendment material (postal) in the initial mixture or extending the composting period, however, led to a higher cost price of compost. It was concluded that reducing the amount of amendment material (postal) and shortening the length of the composting period can reduce the cost price of compost, but may affect the quality of the final compost product. Results showed larger differences between farms than between ratios of cow feces and amendment material, suggesting that compost management practices play an important role.