Dynamic changes of organic nitrogen forms during the composting of different manures

Composting is an effective disposal method for manure waste and nitrogen transformation is an important factor affecting the degree of stability and maturity of manure composting.An aerobic composting simulation experiment was conducted to determine the concentration and speciation of organic nitrogen.The results showed that the acid hydrolysable nitrogen content(%) firstly decreased,then increased during the composting.In some manures,especially in poultry manure,the acid hydrolysable nitrogen content after composting was higher than the initial content,which indicated that manure composting promoted formation of organic nitrogen and reduced nitrogen loss.The concentrations of unhydrolysable nitrogen changed in the opposite direction from the hydrolysable nitrogen.The relative contents(%) of amide nitrogen,amino acid nitrogen and amino sugar nitrogen firstly increased,then decreased during the composting,while the reverse trend occurred for hydrolysable unidentified nitrogen.Linear correlation analysis showed that temperature and pH were the main factors influencing the amino sugar nitrogen(%) content in aerobic manure composting.Similarly,the relative contents(%) of amide nitrogen and hydrolysable unidentified N were affected by temperature,and the acid hydrolysable nitrogen and unhydrolysable nitrogen were most affected by pH.