Effects Of Different N Level On Soil Organic Carbon Stability In Meadow Chernozemic Soil

In this thesis, farmland soil as the research object, using the field simulation experiment, tostudy the effects of soil organic carbon and nitrogen horizontal distribution, total organic carbon,active organic carbon in aggregates and soil humus composition etc. In order to clarify theresponse mechanism of meadow black soil organic carbon stabilization effect on differentnitrogen levels, formulate effective measures for the control of soil carbon reserves and organiccarbon, and provide a basis for reasonable application of fertilizer.The results show that: long term application of different amount of nitrogen fertilizer onsoil aggregates, the effect is more apparent, with the increasing of nitrogen fertilizer, the contentis increased, the maximum value in the nitrogen treatment N240reached, but the impact onsmall aggregates is not obvious. Different nitrogen treatments also has a strong influence on thedistribution of soil organic carbon in aggregates, with the increase of nitrogen organic carbon inaggregates in the distribution of increased, decreased but the rule is not obvious but in smallaggregates.Four consecutive years by applying different nitrogen fertilizer, compared with lessnitrogen (N0), with the increasing amount of nitrogen fertilizer, the total organic carbon inrhizosphere and non rhizosphere soil increased significantly, especially the change of totalorganic carbon content in rhizosphere soil is more obvious, the optimized N fertilizationtreatment of N240with and without n nitrogen fertilizer N0difference of2.36g/kg, nonrhizosphere soil fertilization treatment N240organic carbon content is the highest, thereasonable application of nitrogen fertilizer could improve the content of organic carbon in soil.Effect of N fertilizer application on soil active organic carbon significantly, nitrogen fertilizercan improve the easily oxidized organic carbon content in rhizosphere soil, the overall upwardtrend, the comparison of N0、 N3128.1%, and non rhizosphere soil readily oxidizable organiccarbon content increased with the amount of nitrogen fertilizer had significant change. Effect ofdifferent nitrogen levels on the larger microbial biomass carbon increased, when nitrogenfertilizer, rhizosphere and non rhizosphere soil microbial biomass carbon content increasedsignificantly, but the nitrogen fertilizer dosage over N240after treatment and was significantlydown trend, results show that reasonable application of nitrogen fertilizer can promote the soilmicrobial biomass carbon, but the excessive application of nitrogen fertilizer could inhibit the activity of soil microorganism. Through the active organic carbon acid hydrolysis treatment,rhizosphere and non rhizosphere soil of different nitrogen treatments significantly on the acidhydrolysis of organic carbon, the rhizosphere soil total soluble N240the highest organic carbon,higher than that of N01.94g/kg, non rhizosphere soil treatment of total soluble N270fractionsof organic carbon content was the highest, higher than that of N01.35g/kg. Soluble group HClhydrolysis of total soluble fractions obtained with H2SO4hydrolysis is basically the same,insoluble group trends consistent among. Research shows that the reasonable application ofnitrogen fertilizer can increase the content of soil active organic carbon, is conducive to cropuptake and utilization.Hu Minsu (HM) thick humus content did not show some variation in nitrogen treatments,and no significant change; humus (HE) said the results of assay, with the increasing of nitrogen,compared with blank N0humus organic carbon (HE-C) increased, but not by much, amount ofnitrogen fertilizer on its influence not only significantly, N270increased significantly. The lownitrogen or excessive application of nitrogen fertilizer on soil humus content will not play a rolein promoting, rational fertilization can effectively improve the content of soil humus. Humicsubstances (HA) of Hu Min acid has a significant response mechanism of different nitrogenlevels, from the overall trend with the increase of nitrogen, acid and organic carbon contentN270Hu Min rhizosphere soil (HA-C) content were higher than that of N0, N168, N240, N312treatment for25.5%,20.4%,27.7%,10.4%; non rhizosphere soil organic carbon (HA-C) HuMin acid content increased with the amount of nitrogen, and rhizosphere soil. The highestcontent of N270, N0, N168, N240were17.2%,20.7%, N312respectively,11.6%,9%. Theincrease of nitrogen fertilizer can effectively improve soil Hu Min acid organic carbon (HA-C).Humus acid organic carbon rich quantity (FA-C) of nitrogen fertilizer treatment responsemechanism is not regular, rhizosphere and non rhizosphere soil in different treatments had nosignificant change. The nitrogen treatments on different on soil HA infrared spectrum analysisshowed that with the increase of nitrogen, to increase the content of aliphatic compounds,reduce the polysaccharides and sterol matter content.