Effects Of Different Fertilization Measures On Carbon And Nitrogen Distribution In Reclaimed Soil Aggregates

Land reclamation in mining areas was an important way to maintain the balance of total cultivated land and alleviate the contradiction between human and land.The restoration of soil fertility in reclamation areas was an important purpose of land reclamation in mining areas.The study on the dynamic changes of soil aggregates and organic carbon and nitrogen components in reclaimed coal mining subsidence area was of great significance for systematic analysis of remediation soil improvement mechanism and carbon and nitrogen sequestration in mining areas.In this paper,the reclaimed soil for 4,8 years was studied,Combined with dry sieve and wet sieve method,Fertilization treatments included non-fertilization(CK),manure fertilizer(M),chemical fertilizer(CF),organic fertilizer and Effects of chemical fertilizer application(MCF),biological organic fertilizer and chemical fertilizer mixed fertilizer(MCFB),on the distribution of air-drying aggregates,the impact of the accumulation of organic carbon and nitrogen in aggregates,and the activity of organic carbon and nitrogen in water-stable aggregates.In order to provide a theoretical reference for the soil carbon and nitrogen sequestration mechanism and fertility improvement in coal mining subsidence area.Research indicates:(1)Reclamed soil aggregates have the highest content,the particle size was 2~1mm,and the lowest aggregate content was > 2mm.The distribution characteristics of soil aggregates in 4~8 years after different fertilization measures were not significant,but the content of >2mm aggregates was significantly lower than that of raw soil(RS),which was significantly higher than that of surrounding uncultivated mature soil(US).The mean weight diameter(MWD)and geometric mean diameter(GMD)of the air-dried aggregates with different fertilization treatments at 4 and 8 years were higher than those of mature soil,and the fractal dimension(D)was lower than the fractal dimension of mature soil(D).After 8 years of reclamation,the soil's MWD and GMD increased by 4 years,while the D value did not change.With the decrease of particle size,the content of organic carbon and nitrogen in soil aggregates increased,the aggregates with the largest particle size of 0.5~0.25 mm was the highest,and the organic carbon storage was the highest,with a particle size of 2~1 mm.The soil in 8 years accounted for 23.4% to 36.1%,25.3% to 35.08%.The organic carbon and nitrogen content of each treatment was the highest in the M treatment,but there was no significant difference in the storage of organic carbon and nitrogen between treatments.(2)In different reclamation years,all fertilization treatments were distributed with water stable aggregates of 0.25~0.053 mm,accounting for 37.4%~47.4% of total aggregates.With the increase of re-expansion years,the treatment of M,MCF and MCFB significantly increased the percentage of large-scale water-stable agglomerates(>2mm,2~1mm)in the soil and reduced water-stable micro-aggregates(0.25~0.053 mm).There were no obvious rules for the MWD,GMD and D values of different fertilization treatments in different reclamation years.However,in all fertilization treatments,agglomerates(WSAR)have low stability,with maximum particle sizes > 2 mm and 0.25 ~ 0.053 mm.They were 11.2%~45.1% and 14.9%~26.5%,respectively.The carbon and nitrogen contents of water-stable agglomerates under different treatments were M>MCF,MCFB and CF>CK.The organic carbon and nitrogen in the soil aggregates treated by M for 8 years were 5.5%~40.7% higher than that of CK treatment.56.9%~91.4%(P <0.05).The water-stabilized aggregates in the different treatment years have the highest organic carbon and nitrogen reserves of 0.25~0.053 mm.There was no significant difference in the storage of organic carbon and total nitrogen in water-stable aggregates in the same treatment.The total reserves of all carbon and nitrogen in all grades in the leap year soil were highest in M treatment and significantly higher than other treatments.(3)Reclamation years 4 and 8 years,soluble organic carbon nitrogen(DOC,DON),light organic carbon nitrogen(LFOC,LFON),particulate organic carbon and nitrogen(POC,PON)content of M> CF,MCF,MCFB> CK and M treatments were significantly higher than CK treatment.Among them,compared with CF and CK treatment,M treatment significantly increased the content of PON and LFOC in aggregates with a particle size of 2~1mm for 4 years.Compared with CK treatment,M treatment significantly improved the DOC and DON content of 1~0.5mm particle size aggregates in reclamation 8 years.There was no significant difference in the activity index of CF,MCF and MCFB treated with the same particle size,but the content of active organic carbon and nitrogen in the five fertilization treatments was higher than that raw soil,which was lower than the level of uncultivated mature soil for many years.The regression equation shows that there was significant correlation between total nitrogen and DOC,LFOC and POC.There was a significant correlation between total nitrogen and DON,LFON and PON,and it was consistent with the power function trend.The comprehensive results show that the content of air-dried aggregates of regenerated soil was the highest,which was 2~1mm,and the highest content of water-stable aggregates was 0.25~0.053 mm.As the particle size decreases,the content of organic carbon and nitrogen in the soil aggregates were increased.The organic carbon and nitrogen reserves of air-dried aggregates were highest in the range of 2~1mm,while the organic carbon and nitrogen in water-stable aggregates were the highest in the range of 0.25~0.053 mm.Under the same nutrient input,single application of manure fertilizer can increase the percentage of large-scale water-stable aggregates(>2mm,2~1mm)in the soil to a large extent,and increase the total carbon and nitrogen content in the aggregates.