Comparison of determination methods of organic matter content of organic inorganic compound fertilizers

Dilution-heating method,boiling bath method and oil bath method were used to determine organic matter content of organic-inorganic compound fertilizers,and the precision and accuracy of the three methods compared.The relative standard deviation(RSD)and recovery rate of both boiling bath method and oil bath method are within acceptable range.However,dilution-heating method RSD is 0.55%～6.24%，and enhances with increase of organic matter content in organic-inorganic compound fertilizer.And in some organic-inorganic compound fertilizer samples,the dilution-heating method recovery rate is beyond 100%±5%.Thus in comparison with the boiling bath and oil bath methods,stability and veracity of the dilution-heating method are relatively lower.Adjusted oxidation coefficient of measured organic matter contents of organic inorganic compound fertilizers under dilution-heating,boiling bath method and oil bath method is 1.63，1.49，1.24 respectively;much higher than that of measured organic matter content of soil.