Nutrient turnover and losses during composting of farmyard manure. Results of outdoor experiments over 11 years

Summary

This paper tries to quantify losses of dry matter and nutrients and to look for parameters relevant to the risk of losses. We used data from 14 outdoor experiments carried out in 11 years with cattle manure. Nitrogen (N) rich manures seem to be predestined to have high dry matter and N losses during com-posting. In cases of high temperatures in the thermophilic stage we also observed also high dry matter losses, but not necessaryly high N losses. This may be a hint that an intensive decomposition of or-ganic matter is combined with a strong heat development. However, temperature level was independ-ent from the original N content. K losses were not correlated with any of the investigated parameters, not even with water content. Composted manure was about 60% of the original dry matter (calculated by increase of ash content). However, nutrient losses were much lower. Compared to the original con-tents, approx. 33% N and 39 or 17% K (based on ash contents) have been lost during the entire period of up to 223 days.