Effect of organic manure and chemical fertilizer combined application on the form and distribution of organic nitrogen of black soil

Effect of long-term application of organic manure combined with chemical fertilizer on the forms and distribution of organic nitrogen of black soil were studied. The results that the application of the common rate of NPK fertilizers combined with high rate organic manure could significantly increase the contents of ammonium N, amino acid N and amino sugar N in the topsoil. The range of organic nitrogen forms was nonhydrolysable N>amino acid N >ammonium N>hydrolysable unidentified N>amino sugar N under fertilization conditions. The result also indicated that the contents of all the organic nitrogen forms decreased with the increasing of the depth of the soil profile, which accorded with the tendency of organic matter content, and the C/N ratio changed from 9.03 to 12.49 in different soil layers.