Effect Of Organic Fertilizer Amendment On Soil Organic Carbon Fractions And Aggrigation Status In Drip Irrigated Farmland

【Objective】 Exploring an Appropriate ratio of organic/inorganic fertilizer applicationstrategy is a basis for increasing soil organic carbon content and improving soil fertility infarmland in arid region under drip irrigation condition. In the present study, a three-year filedlocation experiment was estabilised to research on the effects of different amount of organicfertilizer combined with NPK chemical fertilizer on soil organic carbon content, soil organiccarbon fraction and soil aggregation structure as well. Meanwhile, the residual effect oforganic fertilizer combined with chemical fertilizer was investigated by means of wheat potcultivation. The results played a theory supporting role to put forward the effectivefertilization technology of promoting soil organic matter and soil fertility, also providedreference and information for the sustainable and healthy soil use of agricultural fertilizermeasures.【Method】 In the present research, a three-year plot experiment which included CK,100%NPK,80%NPK+OF1,60%NPK+OF2four treatments was established to study theresponse of soil organic carbon characteristic(such as soil organic carbon, labile organiccarbon, soil carbon pool management index and soil microbial biomass) to different ratios oforganic/inorganic fertilizer application. Wet sieve and dry sieve method was used todetermine the content of different particle size, and determined the organic carbon, nitrogen indifferent particle size of aggregate. A pot experiment was to study the effect of differentfertilization on growing development and nutrient uptake of wheat.【Result】(1)Application of3000-6000kg·hm-2organic fertilizer substitute for20%-40%inorganicfertilizer significantly（p <0.05）increased soil organic carbon content, and its incrementdegree of11.4%and15.3%was obtained with both60%NPK+OF2and80%NPK+OF1treatments at the third year (2013),；the increment degree of labile organic carbon was22.6%and53.0%, respectively. At the same time, organic combined with inorganic fertilizer canincrease the soil labile organic carbon, particulate organic carbon, microbial biomass carboncontent.(2)Bulk density of soil was significantly (p <0.05) reduced in the treatment of60%NPK+OF2(1.27g·cm-3) over the100%NPK (1.35g·cm-3) and CK (1.36g·cm-3)treatment. Fertilization treatment increased SOC sequestration as compared to CK treatment,the60%NPK+OF1treatment significantly (p <0.05) increased the SOC pool over the100%NPK.(3) Compared with CK and100%NPK treatment, the application of organic combinedwith inorganic fertilizer can increase the water stable aggregate ratio and decrease thepercentage of aggregate destruction significantly（p <0.05）; whether dry sieved or wet sievedadopted, the mean weight diameter and geometric mean diameter of fertilization treatmentwere higher than CK treatment,60%NPK+OF2treatment was significantly（p <0.05）higherthan CK treatment.(4)Except>2mm and <0.053mm fractions of aggregate, the organic carbon and nitrogen content in soil aggregate reduced along with the reduce of aggregate size; fertilization canincrease the organic carbon and nitrogen content in all the soil aggregates, especially the largemacro-aggregate, the increment degree of organic combined with chemical fertilizationtreatmet was higer than chemical fertilizer only.(5)In pot experiment, compared with CK treatment, the increasing of wheat biomass onaerial part wheat plant nutrition content in the soil which had applied chemical fertiliztiononly was not significant（p <0.05）compared with CK treatment; compared with100%NPKtreatment, the increasing of wheat biomass on aerial part wheat plant nutrition content in80%NPK+OF1treatment fertiliztion was not significan（tp <0.05）, while the60%NPK+OF2treatment increased significantly（p <0.05）.【Conclusion】In conclusion, application of inorganic fertilizer combined with organicfertilizer had the significant (p <0.05) effect on soil organic carbon pool characteristic. Thethree-year plot experiment indicated that application of3000-6000kg·hm-2organic fertilizersubstitute for20%-40%inorganic fertilizer can improve both quantity and quality of soilorganic carbon, decrease soil bulk density, enhance soil aggregate stability, thereby, improvesoil structure and promote soil fertility in drip irrigation condition. Through validation of potexperiment, it was proved that the soil productivity had been improved after three-yearapplication of inorganic fertilizer combined with organic fertilizer.