长期有机无机肥配施协调黑土水稳性团聚体固碳保氮能力OA

Based on a 35-year long-term positioning experiment of Jilin black soil,this study explored the influence of long-term fertilization on the distribution of organic carbon and total nitrogen in the water-stable aggregates of black soil,providing a scientific basis for efficient soil fertilization in the black soil area of Jilin province.Four treatments,namely no fertilization(CK),single application of chemical fertilizer(NPK),partial substitution of nitrogen fertilizer with organic fertilizer(NPKM),and partial substitution of nitrogen fertilizer with straw(NPKS),were selected for the study.The effects of different fertilization treatments on the distribution and stability of soil aggregates,as well as the contents of organic carbon and total nitrogen,were determined.The results showed that long-term fertilization treatment increased the content of soil organic carbon.Compared with CK,soil organic carbon in NPKM,NPKS and NPK treatments was increased by 63.57%,28.68%,and 8.5%,respectively.The combined application of organic and inorganic fertilizers significantly increased the total nitrogen content of the soil.Compared with the NPK treatment,the total nitrogen content of the NPKS and NPKM treatments increased by 18.70%and 54.18%,respectively.Long-term single application of chemical fertilizer(NPK)significantly reduced the content of aggregates at particle size<0.053 mm by 37%,while combined application of organic and inorganic fertilizers showed no significant difference in aggregate content compared with no fertilization.The combined application of organic and inorganic fertilizers had a significant impact on the stability index of aggregates.The average weight diameter and geometric average diameter of NPKM treatment were the highest,which were 1.31 and 0.96,respectively,and the fractal dimension was 2.26,and the stability of aggregates was the highest.Under long-term fertilization,soil organic carbon was mainly enriched in large aggregates>2 and 0.25-2 mm.The organic carbon content in the NPKM treatment was the highest,increasing by 63.6%compared with CK.It significantly increased the contribution rate of organic carbon in aggregates>2 mm in size,with an increase of 115%.Single application of chemical fertilizer(NPK)only significantly increased the contribution rate of organic carbon to small particle size aggregates<0.053 mm,but had no significant effect on the contribution rate of organic carbon to large aggregates.Long-term fertilization mainly affected the gray-scale carbon-nitrogen ratio of aggregates>2 and<0.053 mm.Among them,for aggregates>2 mm,the carbon-nitrogen ratio treated by NPKS treatment was the highest at 12.43,followed by NPK treatment at 11.82 and NPKM treatment at 11.52.For agglomerates<0.053 mm,compared with CK,the NPKM,NPKS,and NPK treatments significantly increased by 34.04%,24.10%,and 17.07%,respectively,while having no significant effect on the carbon-nitrogen ratio of 0.25-2 and 0.053-0.25 mm agglomerates.In conclusion,long-term combined application of organic and inorganic substances effectively increased the proportion of large aggregates in black soil,significantly enhanced the structural stability of soil aggregates and the total nitrogen and organic carbon in the soil.Fertilization could significantly increase the accumulation of organic carbon and total nitrogen in soil aggregates.Combined application of organic and inorganic substances significantly improved the carbon and nitrogen levels in black soil.The enrichment degree of soil carbon and nitrogen increased with the increase of aggregate particle size.Under long-term fertilization,the contribution rate of organic carbon and total nitrogen in black soil aggregates was positively correlated,and the distribution patterns between the two were similar.The carbon and nitrogen of exogenous substances were preferentially retained in large aggregates,promoting the soil's carbon sequestration and nitrogen retention capacity.