Effects Of Long-term Fertilization On The Composition And Structural Characteristics Of Black Soil Organic Matter

Soil humus is a nutrient source.It offers C and N to plants which grow in soil.It plays important role in productivity.Soil fertilization is an effective way to keep and enhance soil fertility.Even though there are many experiments on soil fertilization,the effects of long-term fertilization on HE content and HA constitutive properties is not really enough.The effect of long-term fertilization on black soil HE content and HA constitutive properties is still not in.DOU Sen(1988),ZHANG Jinjing(2001) took black soil from Gong Zhuling as sample to evaluate the change law of HA and FA chemical composition and constitutive properties. But that's just about the change law of the first ten years after fertilization.So the author took the same soil sample both in 1992 and 2005 to do a further research of this.There are 5 kinds of fertilization application in this experiment.They are chemical fertilizer application (NP),organic fertilizer application(M₂,M₄),chemical+organic fertilizer application(M₂+NP,M₄+NP)。We collect soil in 1992(0-20cm),2005(0-20cm) and 2005(20-40cm).Firstly,we use conventional analysis methods to test soil nutrient contents(N,P,K) to evaluate the change law of the soil nutrient contents after fertilization.Secondly,modified humus composition method was adopted to divide Humus into Water floating substance(WFS),Water soluble substance(WSS),HA,FA and HM to evaluate the change law of the humus composition after fertilization.HA constitutive properties was proved byâ–³logK,elemental analysis, differential thermal analysis,ultraviolet spectrum analysis and infrared spectrum analysis.The research shows the results as follows:1) Fertilization can increase N,P and available K in black soil.The content of N,P and available K increase more obviously when apply M₂,M₄,M₂+NP and M₄+NP than it is when apply NP.The content of N,P and available K when apply M₄+NP exceeds M₂+NP.2) Long-term fertilization can increase the amount of soil organic carbon in 0-20cm soil layer of black soil obviously.Chemical + organic fertilizer applications have the best effect.Chemical + organic fertilizer applications can also increase soil organic carbon in 20-40cm soil layer of black soil.But the effect is not significant.3) After long-term fertilization,the amount of HE increases obviously both in 0-20cm soil layer and 20-40cm soil layer of black soil.The amount of HE increases with the organic fertilizer increasing. Chemical fertilizer can only increase the amount of HE in 0-20cm soil layer,but not in 20-40cm soil layer.4) We testedâ–³logK to evaluate the optical properties of humus.In 0-20cm soil layer,the molecular structure of WSS and HE became more complex and that of FA became simpler in 0-20cm soil layer;the molecular structure of HE,HA and FA became simpler after organic fertilizer;the molecular structure of HE and FA became simpler after chemical + organic fertilizer.In 20-40cm soil layer,organic fertilizer and chemical + organic fertilizer can make the molecular structure of HA become simpler.5) By analysis of elemental composition,differential thermal analysis and ultraviolet spectra,we find that organic fertilizer and chemical + organic fertilizer can make oxidation extent and condensation degree decrease.Compared to control,HA after fertilizations are much more youthful,lignin characteristic are more significant,aromaticity are lower.