Groundwater level and fertilizer management is the important environmental factors that affects the soil aggregate pores.In this paper,red paddy soil with a history of 35 years was used as the research material,three long-term fertilization treatments(HO,NO and C)under two groundwater levels(20cm and 80cm)and four fertilization measures changed treatments(HO-C,NO-HO,NO-C,C-NO)under 20 cm groundwater level were selected.the quantitative pore characteristic parameters,such us pores accumulation curves,differential curves,pore basic parameters and pore size distribution were measured by mercury intrusion method to discuss the pore characteristics of soil aggregates with long-term different groundwater levels,different fertilization and after fertilization measures changed.The coupling relationship between pore size distribution characteristics of aggregates and soil physical and chemical indexes were analyzed by correlation analysis and cluster analysis,so as to clarify the driving factors and differences of pore size distribution in different soil management and provide basis for groundwater level and fertilization management of red paddy soil.The main research results are as follows:(1)The pores of the aggregates in the red paddy soil with long-term fertilization of high and low groundwater levels(20 cm and 80 cm)presented a "double peak" pattern,with the maximum and secondary peaks appearing successively in 5 ~ 0.2 μm,0.2 ~ 0.01 μm,and mainly composed of 0.5 ~ 0.005 μm pores(58.17%)and 50 ~ 0.5 μm pores(36.92 %).Groundwater level,fertilization treatment,and the interaction of the two have extremely significant correlation with the total pore volume,total porosity,average pore diameter,pore size distribution and pore permeability of soil aggregates,and the effect of groundwater level is more significant.Compared with the low groundwater level,the high groundwater level was more beneficial to increase the total pore volume,total porosity,average pore diameter,pore permeability of soil aggregates,and also increase the 200 ~ 50 μm pores,50 ~ 0.5 μm,and reduce the 0.5 ~ 0.005μm pores.Compared with chemical fertilization treatment,the application of organic fertilizers(HO and NO)could increase the total pore volume,porosity,average pore diameter and pore permeability of soil aggregates.In addition,the application of organic fertilizer increased the 50 ~ 0.5 μm pores and decreased 0.5 ~ 0.005 μm pores.(2)The pores of red paddy soil aggregates under different fertilization and after fertilization measures alteration under 20 cm underground water level presented a "double peak" pattern,with the maximum and secondary peaks occurring successively at 7 ~ 0.2 μm,0.1 ~ 0.01 μm,mainly composed of 0.5 ~ 0.005 μm pores(57.80%),50 ~ 0.5 μm pores(37.38%).Short-term changes in fertilization measures,whether reducing the application amount of organic fertilizers(HO-C,N-C)or increasing the application amount of organic fertilizer(NO-HO,C-NO),would significantly reduce the total pore volume,porosity,average pore diameter and pore permeability of soil aggregate,at the same time,decrease the porosity by 200 ~ 0.5 μm pores,increase the porosity by 0.5 ~ 0.005 μm pores.(3)Correlation and cluster analysis results showed that the total organic carbon,readily oxidized organic carbon and light fraction organic all affected total pore volume,200 ~ 50 μm pores,50 ~ 0.5 μm pores,and free iron oxide,complexed iron oxide,2 ~ 0.25 mm fine aggregate,0.25 ~ 0.053 mm micro-aggregate all affected 0.5 ~ 0.005 μm pores under the conditions of groundwater level and fertilization measures change.Total organic carbon,readily oxidized organic carbon,and light fraction organic carbon increased the total pore volume,200 ~ 50 μm pores,and 50 ~ 0.5 μm pores,however the free iron oxide,0.25 ~ 0.053 mm micro-aggregate increased 0.5 ~ 0.005 μm pores.Under the condition of groundwater level change,the total pore volume,200 ~ 50 μm pores,and 50 ~ 0.5 μm pores,and 0.5 ~ 0.005 μm pores were also affected by amorphous iron oxide,> 2 mm coarse aggregate,and 2 ~ 0.25 mm fine aggregate,among them,the increase of amorphous iron oxide and > 2mm coarse aggregate would increase the total pore volume,200 ~ 50 μm pores,50 ~ 0.5 μm pores,and the increase of 2 ~ 0.25 mm fine aggregate would increase 0.5 ~ 0.005 μm pores. |