Effects Of Different Conditioners On The Formation Of Soil Aggregates And Organic Carbon Contents And Their Distribution In Reclaimed Soil

The effects of soil conditioner on the composition,stability,organic carbon and functional groups of reclaimed soil can provide theoretical data for the rational improvement and directional cultivation of reclaimed soil structure.In this study,the field experiment was set up in the reclamation base of Tunlan coal mine in Gujiao,Taiyuan City.In addition,the indoor culture experiment was also conducted as verification test for the field experiment.Changes of soil aggregate composition,parameters of soil aggregate stability(content of soil macroaggregate(R>0.25mm),percentage of aggregate destruction(PAD),mean weight diameter(MWD),geometric mean diameter(GMD),fractal dimension(D)),total organic carbon content,POC content,MOC content,and infrared spectrum of soil and aggregates after peat,humic acid and vermiculite addition were studied by a combination of the above methods.The main conclusions are as follows:(1)Vermiculite type conditioner can reduce the bulk density of reclaimed soil rapidly and effectively with timeliness.This effect does not change further with time.Although peat and humic acid addition can not change the bulk density of reclaimed soil rapidly,the effect will gradually appear over time and the effect is better.(2)The addition of peat and humic acid is beneficial to the accumulation of silt particles in the reclaimed soil,reducing the loss of fine particles to a certain extent because of the wind erosion;the addition of vermiculite type conditioner changes the particle size distribution of the reclaimed soil and increases the content of sand particles.(3)Peat and humic acid addition make soil aggregate composition change to the direction of high aggregate content.The addition of peat can also improve the stability of soil mechanical stability aggregates,but the improvement of water stability aggregates is weak.The addition of humic acid can improve the mechanical stability and water stability of the reclaimed soil aggregate,and the effect is the best when the concentration addition amount reached 5%,and the reclaimed soil aggregate is the most stable.Vermiculite type conditioner can increase the content of microaggregate,but its anti erosion ability is poor,and it has no obvious effect on improving the stability of soil aggregate.MWD was positively correlated with GMD and negatively correlated with D.It fully showed that the this three factors can reflect the stability of the reclaimed soil aggregates,and have a high degree of correlation and consistency.(4)Peat and humic acid addition can increase the content of total organic carbon and macroaggregate organic carbon in reclaimed soil.At the same time,the increase of organic carbon content in large aggregates also improves the stability of soil aggregates.Thus,it can further protect the organic carbon in the soil.The addition of peat and humic acid also increased the contribution rate of organic carbon of soil macroaggregate.The effect of vermiculite type conditioner on the content of total organic carbon and organic carbon of each aggregate in reclaimed soil is not obvious,and even decreased.(5)The MOC content of soil and aggregates is basically higher than that of POC.But the addition of peat and humic acid can increase POC content in reclaimed soil,and when the concentration reaches 5%,POC content is higher than MOC,and POC content in > 2mm aggregate is also increased.The effect of vermiculite on POC and MOC content was not obvious in this study.(6)According to the main peak band of infrared spectrum,it can concluded that the compounds of soil organic matter in this study are mainly composed of carboxylic acids,alcohols,aldehydes,amines,phenols,polysaccharides and other substances.The addition of humic acid improver effectively increased the absorbance of soil and aggregates in the range of 3500-3000cm-1,increased the content of hydroxyl and carboxyl,and increased the water stability of reclaimed soil.At the same time,it is further explained that the humic acid modifier enters into the large aggregate first after it is added.(7)As time passed,organic carbon in aggregates will be lost.Although the addition of modifier can increase the content of large aggregates,improve the stability of aggregates and alleviate this phenomenon to a certain extent,it still can not avoid the loss of organic carbon in the process of crushing and recombination of large aggregates.The specific mechanism needs further study.And each index decreased at one year compared with that in six months.It can be seen that when the conditioner is added for 6 months to 1 year,the effect has begun to decrease.The conditioner need be added in time if the quality of reclaimed soil wants to improved continuously.Therefore,the addition of conditioner can improve the reclaimed soil to some extent.Humic acid is the best,peat is the second,vermiculite is the worst.Humic acid can not only reduce soil bulk density,slow down the loss of small particles,increase the mechanical stability and water stability of reclaimed soil,but also increase the content of hydroxyl and carboxyl groups in the soil which are easy to combine with calcareous soil calcium ions,so as to comprehensively increase the stability of reclaimed soil,reduce water and soil loss,protect the organic carbon in soil and aggregates,and increase the content of organic carbon.Humic acid improved the structure and quality of reclaimed soil in many aspects.However,the effect began to decrease at one year,and it needs to be supplemented in time.