Effect of Long-term Located Fertilization on Humus Compositions in Salinized Fluvo-aquic Soil

The experiment was designed to evaluate the influence of long-term located fertilization for 20 years on humus form and composition in light-loamy salinized fluvo-aquic soil(the Alluvial soils by the Yellow River).The results showed that long-term application of organic manure could increase the contents of organic carbon,humus humic acid and fulvic acid and the ratio of Humic acid-Fulvic acid(HA/FA) remarkablely,promote the activation and renewal of organic carbon in soil and improve the quality of soil humus,and the humus content increased with the use level of organic manure.Although chemical fertilizer had the similar effects on the contents of humus and its composition to some extent,their contents were not influenced by the amount of chemical fertilizer.At the same amount of nitrogens combined application of organic and inorganic fertilizers increased HA/FA in arable layer more than constant organic fertilizer.