Research On The Composition And Structure Characteristics Of Humus In Paddy Soil With Different Reclamation Time

In recent years, with the rapid development of economy in our country, CO2emissions alsoincrease year by year, the Chinese government bears the dual pressure which are economicdevelopment and CO2emission reduction. The measures of soil carbon sequestration infarmland are considered as an effective way to reduce atmospheric CO2emission, while thetrend of carbon sequestration in paddy soil is obvious, it has the huge potential. The area ofpaddy soil has reached100million acres in the northeast, it has the largest area of paddy soilwith80million acres in Heilongjiang Province, Jilin and Liaoning Province separately has10million acres. At present, the researches which are about how the soil organic matter changeafter reclamation are less in paddy soil, this article we take paddy soil with different reclamationyears as the research object in Dawa County, Panjin City, Liaoning Province (Saline Paddy Soil)and Jilin Agricultural University (Paddy soil derived from black soil), and use methods ofcombining humus composition modified method and modern scientific, we research the physicaland chemical properties and the content of water-soluble matter (WSS), humic acid (HA), fulvicacid (FA) and humin (Hu) and the structure properties of HA and Hu in paddy soil with differentreclamation years, in order to provide important theoretical basis for further exploring thepotential of carbon sequestration in paddy soil. The main conclusions are as follows:(1) The contents of soil organic matter in surface of paddy soil are higher than subsurface;in surface, soil organic matter contents are the highest in saline paddy soil with reclamation2years, soil organic matter contents are the highest in paddy soil derived from black soil withreclamation30years; in subsurface, soil organic matter contents are the highest in saline paddysoil and paddy soil derived from black soil with reclamation20years, soil organic mattercontents of the paddy soil derived from black soil are higher than that of dry land (CK).(2) With the reclamation years increasing, the pH values decrease gradually in saline paddysoil and increase in the paddy soil derived from black soil.(3) In the surface soil, in saline paddy soil, the available phosphorus and nitrogen contentsare the highest at reclamation2years, the available potassium contents increase first and thendecrease, the available potassium contents are the highest at reclamation20years, in the paddysoil derived from black soil, the available phosphorus and available potassium contents are thehighest at reclamation30years, the available nitrogen contents increase first and then decrease,the available nitrogen contents are the highest at reclamation20years; In the subsurface soil, in saline paddy soil, the available phosphorus and nitrogen contents are the highest at reclamation20years, the change trend of the available potassium is the same with the surface, in the paddysoil derived from black soil, the available phosphorus and available potassium and nitrogencontents are the highest at reclamation20years.(4) In the surface soil, with the reclamation years increasing,HA FA and Hu contents firstdecrease and then increase in saline paddy soil, while the contents of HA increase first and thendecrease, FA contents decrease, the change trend of Hu is not the same with FA in the paddy soilderived from black soil; in the subsurface soil, in saline paddy soil, HA and Hu contents increasefirst and then decrease, while FA contents decrease, in the paddy soil derived from black soil,HA content gradually increase, the change trend of FA content is the opposite of HA, the Hucontent first increase and then decrease.(5) In saline paddy soil, with the reclamation years increasing, PQ values increase firstand then decrease, the humification degree is the highest at reclamation20years in surface andsubsurface soil, the PQ values are63.42%and64.39%, in addition to reclamation20years, thehumification degree in surface is higher than subsurface soil; in black soils, the humificationdegree of paddy soil is higher than that of dry land (CK), with the reclamation years increasing,the PQ values increase in surface and subsurface soil, the humification degree is the highest atreclamation30years, the values of PQ are the largest, they are73.11%and77.11%, thehumification degree in subsurface is higher than the surface.(6) In saline paddy soil, the ΔlgK values and H/C ratios of HA are the smallest atreclamation60years, the high/maximum ratios of heat are the largest, the condensation degreeof HA is the highest, the molecular structure is the most complicated; aliphatic-C/aromatic-C(2920/1620) ratios of HA and Hu are the largest at reclamation20years, they have strongaliphatic characteristics.