| Under the combined effect of natural and human disturbance，the farmland soilorganic carbon (SOC) change is largely,that does not only affect the farmland soilfertility, but also cause elevated CO2concentrations, having an impact on the globalclimate. Confirmed by domestic and foreign scholars: Within the global environment,the balance of soil carbon pool between atmospheric carbon pool is destroyed byhuman cultivation, making organic carbon in soil oxidized to CO2and otherreleasing forms, thus increasing the CO2in air. Now, with the international emphasison the emissions of greenhouse gases and the security food production, farmland soilorganic carbon change has become the focus by the international community, thusincreasing the potentiality of carbon sequestration in agricultural soils has greatsignificance.So, under the change of global climate, deeply research on thedistribution characteristics of soil organic carbon,and affecting factors of carbonsequestration, which are important to the preparation of farm management practices,enhancing the potentiality of soil carbon, correctly evaluating the impact ofagricultural activities on worldwide climate change and its response.The paper relies on the18topics of geological and agriculture surveys in landconsolidation in2010-Geological and agriculture Surveys of land consolidation areain Tuojiang village, Neijiang City,“Golden Land Project” in Sichuan province and thegeochemical assessment of mustard origins in Neijiang City-The key project ofEducation Department in Sichuan province. Strictly followed" the implementationdetails of agricultural and geological survey in Sichuan Golden Land Project ",wecarried out field integrated research in typical study area-Tuojiang village, NeijiangCity, collected180samples of the surface soil (average density is16/km2), collected 12soil samples in measurementing Vertical profile made8m layered soil,11soilsamples in measurementing10km integrated geological cross-section,17soilsamplesroot crops,then, tested samples interior, making full of GIS, Spss etc., basedon the integration of geochemical, geological and other information on agriculture,and comprehensively analyzed the distribution of farmland soil organic carbon,estimated the holding capacity of farmland soil carbon on Tuojiang River Basin(Neijiang), the results are as follows:1. The soil organic carbon coefficient in arable layer on Tuojiang River Basin(Neijiang segment) changes a lot, and is uneven, concerned with the hydrothermalchange, topography and other closely related actors in hilly area, but We’re not surewhether it concerns with great variation in soil pH, pending further study. Ingeological and horizontal section, the higher content organic carbon points mainly inthe forest and rice fields, and lower mainly distributed in the dry land; From theregional distribution point of view，the soil organic carbon content in northern part ishigher than the south, paddy field of centralized distribution area is higher than inother regions; From the spatial distribution, the high organic carbon content areas, thesoil is mainly neutral or slightly alkaline, while areas with low organic carbon contentand soil environmental performance is more weakly acidic; farmland soil organiccarbon content of root crops survey data changes, which is different crops types,different soil types, different geographical conditions etc. there are some relationships.2. Farmland soil organic carbon associated with other geochemical elementsshows that: in dry land, farmland soil organic carbon with B, K2O, Mn, Mo, N,Na2O, P, S, Se, SiO2, Fe2O3etc. all have significant correlation.(p <0.01); asignificant correlation (p <0.05) between nutrients MgO、I and soil organic carbon;and highly significant correlation (p <0.01) with heavy metal elements As, Cd, Cu,Hg, Ni, Pb, Zn and other, while Cr is not strong; in available elements, no highlysignificant correlation, but also only effective Fe, slow-K with soil organic carbonhas significant correlation (p <0.05), the effective remaining elements with the soilorganic carbon are unobvious. In paddy soil, the geochemical elements such as CaO,I, K2O, N, Na2O, S, Se, SiO2, Fe2O3, are significantly correlated (p <0.01);nutritional elements MgO, P, Mo between soil organic carbon,there is a significantcorrelation; highly significant correlation (p <0.01) with As, Cd, Hg, Ni, Pb, Zn andother heavy metals content, Cu elements and soil organic carbon was significantlycorrelated (p <0.05), but similar to the Cr element and dryland, there is nocorrelation. Effective state elements, only the effective P, slow-K have a highlysignificant correlation (p <0.01), available K and organic carbon effects aresignificant correlations (p <0.05), others have no obvious correlation with soilorganic carbon. 3. By analyzing the impact of agricultural soil organic carbon in the typicalstudy area, the results show that:(1)Return to the stratum has an influence on the formation of soil organiccarbon, The Jurassic Shaxi Temple group four (J2s4) weathering of rocks on soilorganic carbon contribution higher than Jurassic Shaximiao three sections (J2s3),namely The Jurassic Shaxi Temple group four (J2s4) on soil organic carboncontribution higher than The Jurassic Shaximiao three sections (J2s3).(2)From the Quaternary’s cause analysis, the amount of soil organic carbon(SOC) in the typical study area: alluvial material (Qdpl)> alluvium (Qal)> residual talus(Qeld)> residual material (Qel), There is a relationship between the Quaternary and soilorganic carbon.(3)From the analysis of different types of soil: Purple dry land soil organiccarbon content between0.6%to2.94%, the average is1.08%,coefficient of variationis29.4%, more uniform distribution; while paddy soil organic carbon (SOC) contentis higher, between0.87%~3.57%, the average is1.95%, the coefficient of variationis34.1%, also more evenly distributed, but its content is greater than the change inpurple soil. That the average content of organic carbon in agricultural soils is: paddysoil> purple soil. From soil organic carbon content differences of view: paddy soil>purple soil.(4)From the analysis of different land use, the content of organic carbonirrigation is high in paddy soil, but varies largely, while in dryland content is lowerlevels,but relatively small fluctuates, more uniform distribution. From the effects ofdifferent soil types and land use on soil organic carbon content can be drawn,wetlands play an important role for carbon sequestration. Should pay attention toprotect the wetlands, not only have a significant role in improving the ecologicalenvironment, but also protects the sustainable economic and social development.(5)Under different land use, soil organic carbon content distributed as follows:irrigated paddy (1.95%)> wasteland (1.55%)> woodland (1.11%)> drylands (1.07%).the magnitude of changes of soil organic carbon content (coefficient of variation) isas follows: irrigated paddy field (0.341)> Woodland (0.302)> drylands (0.292)>wasteland (0.119), that is high in irrigated paddy soils, but the magnitude changeslargely, dry land content is relatively lower,small amplitude and more uniformdistribution.(6)From the view of different cropping systems, double cropping system in thearea primarily for flood and drought crop rotation or drought drought crop rotation,three harvests a year mainly are stem mustard (mustard) growing areas. soil organiccarbon under different cropping systems on Tuojiang River Basin (Neijiang section) mainly as follows: on the whole, two crops a year soil organic carbon content(1.12%) higher than three crops a year (0.82%).Three crops a year, but the maximumindividual points higher than two crops a year, is due to be further confirmed Thetwo crops a year in soil organic carbon content (0.295) are more stable than threecrops a year organic carbon content (0.40), changes a little in the difference.Therefore, only we can pay attention to land recuperation, focus on crop rotation,there will be more soil organic carbon effectively retaining, sustainable ecologicaland economic development.(7)By analyzing the correlation beween soil organic carbon content on TuojiangRiver Basin (Neijiang) and soil environment (pH), the results show that: thecorrelation between farmland soil organic carbon content and pH value is notsignificant, that the pH of soil affects the amount of carbon content, distribution andstability not obviously, the reason is yet to be studied.4. Soil organic carbon storage and density of the Yangtze River are larger, andTuojiang River Basin belongs to the tributary of the Yangtze River, So, it shows thatTuojiang River Basin plays a very important role. By comparing survey data fiveyears ago and five years later of paddy field、dry land on Tuojiang River Basin(Neijiang), the simulation results are: Tuojiang River Basin (Neijiang section)upland soil organic carbon will reach equilibrium in34.19years;Tuojiang RiverBasin (Neijiang section) paddy soil organic carbon will reach equilibrium in29.74years.5. Based on large data resources and simulation, the results are as follows: soilorganic carbon’s average saturation content in upland of Tuo River Basin (Neijiangsegment) farmland is1.1741%,the same in the paddy is1.1418%. In typical studyarea,per unit area of paddy soil carbon sequestration capacity is23.48t/hm2, dry landis22.84t/hm2; reserves of organic carbon: irrigation paddy is3713t, upland is15680t,the total is19393t. According to evaluation, the regional soil organic carbonsequestration capacity are as follows: paddy soil is1820399t, Alluvial soil is395321t, purple soil is2330674t, rendzina is137503t, yellow loam is6445t. The totalamount of holding soil organic carbon(SOC) capacity on Tuojiang basin (Neijiangsection) is4690342t. |
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