Dynamic change of organic matter in the black soil under long-term fertilization

The effect of long-term fertilization on organic matter in the black soil was studied under a 30-year long-term combined application of manure and chemical fertilizer in Gongzhuling,Jilin province.The results indicated that the soil organic matter(SOM) was decreased with 30-year long-term chemical fertilization alone or no fertilization(M0 plot),the decline rate ranged from 2.1% to 7.9%.The SOM was increased with moderate(M2 plot) and high rate manure(M4 plot) fertilization,the rate of increase ranged from 42.2% to 50.0% and from 81.5% to 94.7%.The SOM increased slowly from 1980 to 1992,with the lower increase magnitude of 2.4% and 9.3% in the M2 and M4 plots,respectively.While after 12 years fertilization the SOM contents in the M2 and M4 plots have higher magnitude of 41.4% and 71.5% respectively in the year of 2010 due to the increase of organic matter in the manure.The SOM contents were significantly different among the treatments with different rate of manure but the same rate of chemical fertilizer.Whereas the SOM contents were not different among the treatments with different rate of chemical fertilizer but the same rate of manure.The results implicated that the SOM content in the black soil could be increased through long-term application of manure.The selected rate and quality of manure was the main measure to improve the SOM in the black soil.The high rate and quality of manure could rapidly increase the SOM content in the black soil.