SỰ THAY ĐỔI HÀM LƯỢNG ĐẠM TRONG PHÂN LỢN QUA QUÁ TRÌNH LƯU TRỮ PHÂN LỎNG VÀ Ủ PHÂN RẮN

A high proportion of the plant nutrients present in animal feed are excreted and therefore animal manure can be an important source of nitrogen (N) for crop production if losses of plant nutrients to the environment during storage and processing are minimized. This study examined gaseous N losses from stored pig slurry and composting manure as affected by protein and fibre content in feed to the pigs and manure management. Two slurry storage treatments (with and without cover) and three additives to solid manure composting (straw only; straw + lime; straw + superphosphate) were examined for three common pig feed rations in Vietnam (low protein, high fibre; medium protein, medium fibre; high protein, low fibre). Feed ration was found to affect the N content in pig slurry or manure and thus potential N losses. Total gaseous N losses from covered slurry storage were 0.25-0.30 of initial N content, while those from uncovered slurry were 0.60-0.70. After 90 days of storage, 1.15-1.20 of the initial NH4-N was found in covered slurry and 0.40-0.50 in uncovered. Total N losses during composting with superphosphate were 0.25-0.35 of initial total N, while with lime or straw the total N losses were 0.45-0.55. With added superphosphate 1.25-1.60 of the initial NH4-N in manure was found in the compost after 80 days, compared with only 0.11-0.22 for lime and 0.22-0.36 for straw only. Covering stored slurry and addition of superphosphate when composting solid pig manure are thus important methods for Vietnamese farmers to minimize N losses and produce compost with a high content of plant-available N.