| Application of organic material could increase soil organic carbon,improve soil structure,promote crop growth and production,and is of significance to the ability of soil organic carbon sequestration.At present,the effect of organic materials on soil organic carbon has achieved a series of results,but the changes of soil organic carbon and characteristic of aggregates in the rhizosphere soil of different crop after application of organic material were not clear.In this paper,the experiments were carried out via two years field experiment in Jilin Agriculture University experimental field.Three kinds of crops(corn,soybean,cabbage)were selected in the experiments and each crop applied four fertilizer treaments,as followed chemical fertilizer(CK),maize straw,leaves and poultry manure,respectively.The dynamic changes of TOC,DOC,EOC,MBC,POC were measured.Then the effect of combining forms of humus,the composition and properties of humus were measured.Meanwhile the effects of aggregate composition and distribution of organic carbon among aggregate size fractions were analyzed.The effects of organic materials on the components of actived organic carbon,the characteristics of humic substance and the stability of aggregates in rhizosphere soil of different crops were discussed.The study provided scientific basis for evaluating the fertilizer efficiency of organic materials on the rhizosphere soil of different crops.The main results were as follows:(1)Among different treatments,the average content of TOC and EOC in soybean rhizosphere soil were remarkably lower than that of corn and cabbage.The content of POC in soybean rhizosphere soil was higher than that of cabbage.After 90 days of applying straw,the content of EOC in corn and cabbage rhizosphere soil was increased obviously,and the content of EOC in soybean rhizosphere soil was increased on the 120 th days,the soil organic carbon oxidation stability was increased.After 90 days,the content of DOC in cabbage and carbon rhizosphere soil with application of straw were increased obviously,and the availability was improved.Straw significantly improved the contents of MBC in corn and soybean rhizosphere soil.After 90 days,straw remarkably increased the content of POC in rhizosphere soil of crops on 120 th days.The improvement of organic materials on TOC in rhizosphere soil was obviously,the effectivity of staw was best.To sum up,returning straw was effective way to increase contents of total organic carbon and active organic carbon.Correlation analysis showed EOC correlated most positively with TOC,which could be deemed to be the sensitive index reflecting the change of total organic carbon in rhizosphere soil.(2)Organic materials significantly increased the ratio of loosely/tightly combined humus in rhizosphere soil of corn and soybean,it improved quality of humus.Compared with CK,the application of organic materials significantly increased the organic carbon contents of HA in rhizosphere soil of different crops by 34%~55%.Organic materials showed no significant effect on carbon contents of FA.The effect of organic materials on the PQ values(the ratio of HA/(HA+FA))were varied with different crops.The maize straw and poultry manure treatments had similar effects on PQ values in rhizosphere soil of corn and soybean,and the poultry manure significantly increased PQ values in rhizosphere soil of cabbage.The application of organic materials simplified the structure of FA,and complicated the structure of HA,increased the contents of nitrogen containing groups of HA,the effect of maize straw was the most obvious.In general,organic materials showed better benefit effect on soil fertilization than chemical fertilizer.The effect of poultry manure on rhizosphere soil of cabbage was the most significant,maize straw and poultry manure treatments had similar effects on the rhizosphere soil of corn and soybean.(3)Water stable macro-aggregate(WSA>0.25mm)in rhizosphere soil of three crops were the dominant position in the fraction of water-stable aggregate.Soybean roots were bad for the formation of WSA>0.25 mm.Compared with CK,the application of straw has significantly increased the contents of water stable macro-aggregate in rhizosphere soil of maize and soybean,influenced on the amount of organic carbon of 2-0.25 mm aggregate remarkably.Soil organic carbon of aggregate was primarily distributed in 2-0.25 mm fraction,followed by 0.25-0.053 mm fraction,and it was lowest in <0.053 mm fraction.The organic carbon contents of aggregate(> 2mm,2-0.25 mm,0.25-0.053mm)in rhizosphere soil of maize and soybean were significantly increased with straw application.The effect of crop-fertilizer interaction on the contribution rate of soil organic carbon in the <0.053 mm aggregate was obvious.In general,returning straw is effective to improve soil organic carbon,and increase stability and ability of carbon sequestration of aggregate in rhizosphere soil of maize and soybean. |
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