Effects of long-term fertilization on the soil aggregates and organic carbon components in wheat fields of Loess Plateau
Enhancing the soil organic carbon(SOC)pool and aggregate stability is of great significance for fertility and low-carbon green agricultural development.This study aimed to investigate the effects of five different fertilizers on the characteristics of soil aggregate attribution and carbon component changes based on data from the dryland winter wheat growing area in southern Shanxi Province,China.Five treatments were used:no fertilization(CK),conventional fertilization(FP),optimized fertilizer(OF),optimized fertilizer+organic fertilizer(OFM),and optimized fertilizer+biological organic fertilizer(OFB).The results showed that the predominant size fractions were large macroaggregates(2-0.25 mm)and macroaggregates(0.25-0.053 mm)in different fertilization treatments,and the lowest content was found in the＞2 mm fraction.All fertilization treatments improved soil water-stable aggregates and SOC,with the most significant effects observed in the OFM and OFB treatments.SOC in different fertilization treatments was mainly distributed in the 2-0.25 mm and 0.25-0.053 mm fractions of aggregates,accounting for approximately 72.97％-76.65％of the total SOC content.The OFB and OFM treatments were more conducive to the migration of organic carbon to larger aggregates,and the SOC content of the 2-0.25 mm fractions increased,as did the content of the light fraction organic carbon(LFOC).The long-term application of chemical fertilizers(OF and FP),which accelerate the decomposition of humic carbon(HUC)and reduce the humification of SOC,was not conducive to organic carbon sequestration.However,the contents of fulvic acid carbon(FAC),humic acid carbon(HAC),and HUC in the original soil increased in the OFM and OFB treatments,and the content of HAC was higher than that of FAC,which promoted the formation of soil aggregates.Redundancy analysis showed that SOC was positively correlated with LFOC,FAC,and HAC,and positively correlated with the content of soil macroaggregates(＞2 mm and 2-0.25 mm fraction).Soil geometric mean diameter(GMD),SOC,and HAC were important factors affecting the distribution and stability of soil aggregates,based on the results obtained.In conclusion,the stability of soil aggregates and the SOC content of aggregates with different particle sizes were enhanced by the different fertilization treatments.Combined application of organic and inorganic fertilizers can increase the content of large aggregates(2-0.25 mm),and total organic carbon and organic carbon components to a greater extent,thus enhancing water-stable aggregates stability.
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