Response Of Reclaimed Soil Fertility Properties,Organic Carbon And Nitrogen Pools To Fertilization In Coal Mining Subsidence Area

Land reclamation in mining area is an important way to maintain the balance of total cultivated land and alleviate the contradiction between population and land resources.Improvement of soil fertility is the ultimate goal of soil reclamation in mining area,and soil organic carbon or nitrogen pool capacity is an important index to evaluate the effect of soil reclamation and fertilization.A field experiment was conducted on the long-term experimental base of reclaimed soil to study change of soil organic matter,alkali-hydrolyzale nitrogen,available phosphorus,available potassium,pH,CEC,EC and microaggregates,and the evolution of organic carbon and nitrogen pools in different reclamation year’s soil.The fertilization treatments including no fertilizer(CK),fertilizer only(CF),manure only(M)and 50%chemical fertilizers co-applied with 50%manure(MCF).So as to reveal the response mechanism of the soil fertility properties,organic carbon and nitrogen pools to different fertilization measures,then provide scientific basis for effective and rapid increase of soil fertility in mining areas.The main findings and conclusions are as follows:(1)There was no significant difference in soil pH and electrical conductivity under different reclamation years,different fertilization measures and 1 m soil profile,which ranged from 8.03 to 8.43 and 0.11 to 0.25 dS/m,respectively.The fertility level of reclaimed soil increased gradually with the increase of reclamation years.The effects of single organic manure on alkali-hydrolyzed nitrogen,available phosphorus,available potassium,organic matter and cation exchange capacity in 0-20 cm soil layer(surface soil)were better than those of single fertilizer or fertilizer combined organic manure,but there was no significant change in soil properties of 20-100cm under each treatment.At the same time,compared with other treatments,the water holding capacity of reclaimed 0-60cm soil was significantly increased by applying organic manure.In addition,there were a lot of nitrate residues in 20-60cm soil layer treated with single fertilizer and fertilizer combined organic manure for 7 years of reclamation.Reclamation years and fertilization measures did not cause the change of distribution characteristics of soil microaggregates.The proportion of 0.01-0.05mm microaggregates was the highest in all treatments,and reached up to 40%.Different reclamation years and fertilization treatments had no significant effect on the content of microaggregates in the same particle-size.(2)The content of soil organic carbon increased with the increase of reclamation years,and fertilization could increase the content of soil organic carbon in coal mining subsidence area.The relationships among the five kinds of active organic carbon were as follows:microbial carbon(MBC)>soluble organic carbon(DSOC)>light group organic carbon(LSOC)>easily oxidized organic carbon(ROOC)>water-soluble organic carbon(WSOC).WSOC and MBC account for 1%～5%of total organic carbon,while DSOC,ROOC and LSOC account for 14%～40%of total organic carbon.WSOC,DSOC,ROOC,LSOC,MBC and MBC in 7-year reclamation soil were 20%～100%,10.31%～68.29%,60%～186.83%,15.29%～141.28%,and 27.45%～76.23%higher than those in 1-year reclamation soil,respectively.The content of active organic carbon of single organic manure was the highest among all the treatments.As the inert carbon components,the heavy fraction and the stable organic carbon had no significant change with the increase of reclamation years,and there was no significant difference among the fertilization treatments.As slowly available carbon,particulate organic carbon(POC)also showed an increasing trend with the increase of reclamation years.The soil POC increased by 17.91%to 39.93%and 47.47%to 106.25%in 7 years compared with that in 3 years and 1 year,respectively.The POC of organic manure treatment was the highest in all fertilization treatments.There was no significant effect on all organic carbon components in the control treatment without fertilization.The effect of single chemical fertilizer treatment on WSOC content was significant,while other organic carbon components did not change significantly.The contents of active organic carbon and slowly available carbon(POC)in organic fertilizer and organic-inorganic combination treatments increased significantly,but the inert organic carbon components did not change significantly.(3)Soil organic nitrogen components increased with the increase of reclamation years,and fertilization could increase the content of soil organic nitrogen components in coal mining subsidence areas.In reclaimed soil,ammonium acid nitrogen,amino sugar nitrogen,amino acid nitrogen and unknown amino acid nitrogen account for 6.31%～22.79%,3.69%～27.82%,34.09%～48.08%and 24.09%～41.92%of the total hydrolizable nitrogen,respectively.After 7 years of reclamation,the contents of hydrolizable nitrogen,ammonia nitrogen,amino acid nitrogen and hydrolysable unknown nitrogen in soil were 46.15%～88.57%,178.97%～817.21%,12%～30.3%and 20.51%～36.04%higher than those in 1-year reclamation soil,respectively.The organic nitrogen components of single organic manure was the highest in all fertilization treatments.The content of amino sugar nitrogen and microbial biomass nitrogen 7-year reclamation soil increase by 1.87%-133.5%and 62.8%-396.07%,respectively,and fertilizer combined organic manure among the treatments was higher than that of other treatments.All organic nitrogen components in the control treatment without fertilization did significant changed.Under the treatment of chemical fertilizer alone,the contents of total nitrogen,ammonium nitrogen and microbial biomass nitrogen increased significantly,but had little effect on other organic nitrogen components.The content of other organic nitrogen components significantly increased in the treatment of single organic fertilizer,except for the unknown nitrogen and microbial biomass nitrogen.The contents of other organic nitrogen components except amino acid nitrogen and acidolysis unknown nitrogen were significantly increased by combined organic and inorganic treatments.In conclusion,long-term fertilization can improve the fertility characteristics of reclaimed soil and significantly increase the soil organic active carbon pool and organic nitrogen pool capacity.Under the same nutrient supply condition,the single organic manure has the best efficiency.