| Soil organic carbon and humus are important indicators for assessing soil quality and are of great significance for soil remediation and improvement.In this paper,purple soil in hilly areas of Sichuan Province is taken as the research object.Purple soil can be divided into alkaline,neutral and acidic subspecies.In this paper,the alkaline purple soil collected from Linshan Township,Yanting County,Sichuan Province is selected?Note:After verification,the pH value of alkaline purple soil is greater than 8,which is alkaline,in this paper,it is called alkaline purple soil?.The neutral purple soil in Huachi Township,Renshou County and the acid purple soil in Leshan City are studied through field sampling and indoor analysis.Distribution and structural characteristics.It provides a reference for the rational use of land and the coordination of land use patterns in hilly areas of Sichuan.At the same time,taking Yanting alkaline purple soil as the research object,the humification law of forest litter and crop straw was studied,which could provide theoretical reference for the efficient recycling of straw and the effect of litter on soil organic matter.The main conclusions are as follows:1)There are significant differences in the distribution of organic carbon and humus carbon in vertical profiles of different types of soils and different land use patterns.The total difference of organic carbon in alkaline,neutral and acidic purple soil profiles was as follows:Acidic Purple Soil>neutral purple soil>alkaline purple soil.Under different land use patterns,the organic carbon content of alkaline purple soil was woodland>dryland>paddy field,and that of neutral and acidic purple soil was paddy field>woodland>dryland.2)The humus content,carbon content and HA/FA value of the surface layer of alkaline purple soil were as follows:alkaline purple soil<neutral purple soil<Acidic Purple soil.The humus content and carbon content of reconstituted soil in the surface layer of forest land were 11.919g/kg and 11.403g/kg,respectively;the humus content and carbon content of reconstituted soil in the surface layer of dry land were 7.919g/kg and 7.107g/kg;the humus content and carbon content of reconstituted soil in the surface layer of paddy field were 14.788 g/kg and 13.957g/kg,respectively:paddy field>forest land>dry land.The HA/FA value of Soil Humus in Dryland was the highest?1.98?,indicating that the humification degree of Soil Humus in Dryland was the strongest.The HA/FA value of paddy field soil humus is 1,and that of forest soil humus is 0.467.The humification degree of paddy field soil humus is the worst.3)The content of humus carbon in different types of soils under different land use patterns was as follows:Humin?Hu?>Fulvic acid?FA?>Humic acid?HA?,and the content of humus carbon in different combined forms was as follows:tight-bound>loose-bound>stable-bound.In the soil profile,the content of humus and component carbon,reconstituted soil carbon and combined humus decreased with the deepening of soil layer,and the content of humin and compact humus accounted for more than 50%of total humus,respectively.The HA/FA values of 20-40cm soil layers in alkaline,neutral and acidic purple soils were higher than those of 0-20 cm soil layers and 40-60 cm soil layers,indicating that the aggregation degree of humus in 20-40 cm soil layers was higher.The ratio of loose-bound humus content to tight-bound humus content in different types of soils is 0.227-0.536,which is small on the whole,indicating that purple soil humus in hilly areas of Sichuan has strong storage capacity.The HA/FA values of Soil Humus in Dryland and paddy field were1.272-1.979,0.737-1.696 and 0.666-0.932 respectively.The humification degree of Soil Humus in Dryland and paddy field was obtained.)The results showed that the quality of humus in paddy and dryland soil was better than that in forest soil.Under different land use patterns,the ratio of loosely bound humus to tightly bound humus in soil profile was as follows:dryland>paddy field>woodland,which indicated that the activity of Soil Humus in Dryland was the highest.It also shows that the humus activity and storage capacity of different types of soils in hilly areas of central Sichuan are strong under different utilization modes.5)The decomposition of straw and litter belong to the decomposition of organic matter.The decomposition rate increases with the extension of decomposition time and the residue decreases.After decomposition for one year,the decomposition rate of rice straw was 99.61%,the decomposition rates of nutrient elements C,N,P and K were 99.73%,99.07%,96.44%and 99.16%,respectively;the decomposition rates of corn straw were 96.89%,and the decomposition rates of nutrient elements C,N,P and K were 97.36%,93.23%,99.16%,99.53%,99.93%respectively.Therefore,in the process of straw decomposition,nutrients in straw enter the soil and become nutrients for plant growth.The residual part of the decomposed straw can also become organic matter in the soil.This paper not only analyzed the annual yield of litter and its components in Yanting forest land in 2018,but also studied the humification law of litter in 210 days.Firstly,the results of litter quantity experiment showed that the annual litter yield of mixed alder-cypress forest was 272.916g·m-2·yr-1,and the proportion of each component in total yield was 24.94%for branches,68.14%for leaves and 6.92%for fruits,respectively.Deciduous leaves occupy the main part of litter,and the trend of change is consistent with the change of total litter yield.Secondly,in the process of litter humification,the decomposition rate of litter increases with the prolongation of decomposition time.The release rate of C,N,P and K increased with the prolongation of decomposition time.The release rate of K was higher than that of C,N and P.The release rate of C and P was in the middle,and the release rate of N was the smallest,and the growth rate was slow.After 210 days of decomposition,the content of humus in litter residues decreased from 22.568%to 7.1663%,the content of HA and FA decreased,and the content of organic carbon decreased slowly.W?HA?/w?FA?increased at first and then decreased during humification,which indicated that humification of litter was beneficial to the formation of humic acid.At 210d,the content of humic acid and fulvic acid was similar.Therefore,the accumulation of humus during humification is very important for soil formation.Therefore,returning straw to the field can not only make full use of the remaining straw,but also increase the organic matter and nutrients in the soil,enhance the soil fertility,and provide a theoretical basis for the improvement of agricultural soil fertility and the rational use of land.Humification of forest litter can increase soil organic carbon and increase soil carbon storage. |
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