Cattle manure management in East Africa: Review of manure quality and nutrient losses and scenarios for cattle and manure management

Manure is an important source of nutrients for many smallholder farmers in East Africa, with cattle manure being the dominant type. Information on nutrient losses between excretion and application of manure is still limited under smallholder conditions in the tropics, due to the wide variation in farming conditions and variation in livestock and manure management. In the first part of this report, quality of mainly cattle manure, and nutrient losses during manure collection and storage are reviewed. The second part explores and discusses effects of eight cattle and manure management scenarios on nutrient and manure availability. Nutrient excretion and manure quality strongly vary, due to variation in feed quality and intake, addition of organic material, nutrient losses and contamination with soil. Total nitrogen content of manure on a dry matter basis ranges from below 0.5 to over 4%. Contents of soluble nitrogen (ammonia N) also strongly vary. Nutrient and carbon losses during manure collection and storage vary substantially, depending on cattle and manure management. Nitrogen losses for example may vary from less than 10% to about 90%. Nitrogen losses tend to be lower for more compact and anaerobic manure storage systems and for manures with higher carbon to nitrogen ratios. On the basis of the review, a summary table is constructed, giving indicative nutrient losses for six different systems of collection and storage of cattle manure. Losses are indicated separately for dung and urine, because of the high risk for losses of soluble nutrients from urine. High, moderate and low loss levels are indicated to account for the large variation in collection and storage conditions. Differences in relative losses among manure storage systems are larger for urine and smaller under favorable storage conditions. Nitrogen losses indicated in Table 6 vary from 20-100% for urine and from 5-50% for faeces. Losses of phosphorus from faeces vary from 3-30% and potassium losses from urine from 5-80%. The proposed losses are used for a subsequent scenario study