[Effects of Different Modifiers on Aggregates and Organic Carbon in Acidic Purple Soil]

The aim of this study was to examine the effects of different modifiers on the changes in aggregates and organic carbon in acidic purple soil， providing a scientific basis for the remediation of acidic purple soil. Using purple soil as the research object， a total of six treatments were set up， including no fertilization （CK）， single fertilization （F）， fertilization with lime （SF）， fertilization with organic fertilizer （OM）， fertilization with biochar （BF）， and fertilization with distiller's grains ash （JZ）. We compared the composition of aggregates in acidic purple soil under the application of different modifiers， as well as the distribution pattern of organic carbon in aggregates of different particle sizes. Combined with the stability indicators of aggregates， we sought to clarify the impact of different modifiers on the structure of aggregates in acidic purple soil. The results showed that fertilization significantly increased the soil pH， with the JZ treatment being the most effective. Fertilization significantly increased soil organic matter content， with the OM treatment showing the largest increase. The BF and OM treatments significantly reduced soil bulk density， whereas the SF and BF treatments significantly increased soil moisture content （P < 0.05）. All treatments used < 0.25 mm aggregates as the dominant particle size. Fertilization could significantly increase the content of large aggregates （aggregate structure units with diameter > 0.25 mm）. At the same time， fertilization treatments significantly increased the soil geometric mean diameter （GMD）， average weight diameter （MWD）， and R_0.25 value （ > 0.25 mm aggregate content） and reduced the fractal cone number （D） and aggregate destruction rate （PAD） values （P < 0.05）. Fertilization also promoted the aggregation and stability of soil aggregates， with the OM treatment having the greatest effect. Compared with that in the CK treatment， fertilization could significantly increase soil organic carbon content by 31.71%-209.67%， with the OM treatment showing the most significant change. Different treatments of soil organic carbon were mainly distributed in large aggregates. Compared with that in the CK treatment， each treatment significantly increased the contribution rate of organic carbon in large aggregates by 19.34%-47.76%， with the OM treatment having the most significant effect （P < 0.05）. In general， chemical fertilizer combined with organic fertilizer could promote the formation of large aggregates in acidic purple soil， improve the stability of soil aggregates， and increase the content of soil organic carbon， which is an effective measure to improve the soil structure and improve the quality of acidic purple soil.