| The activities of human frequently and climate change,finally, make soil organic carbon into carbon sources or sinks, the role played by the farmland of organic carbon in the carbon cycle can not be replaced by other carbon pools,through field experiments we make soil organic carbon as center.Researching the effect of contents and compositions of organic carbon and its fractions in soils from the high-yield spring maize-based demonstrative croplands provide a favorable regulatory measures as increase grain yield.the results of the study are as follows:1.The research of organic carbon from the high-yield spring maize-based demonstrative croplands located at Lishu county, Jilin province, the middle of Songliao Plain,indicated that,The contents of soil organic carbon and its fractions of high-yield soil,The total organic carbon,Easily oxidizable organic carbon,Water soluble organic carbon, Particulate organic carbon, FA and HA contents, with ranges of4.49-12.4,0.46-2.04,0.096-0.174,0.65-3.40,0.71-2.52andl.61-3.75g·kg-1The control were1.99-9.28,1.05-2.85,0.085-0.125,0.62-1.80,0.18-1.59and0.61-2.80g·kg-1compared with the control, the contents of SOC and its fractions were higher, The organic carbon contents of<1mm dry aggregates were generally higher in the high-yield than in the control soils,The organic carbon contents of water-stable aggregates mainly distributed in the2-0.25mm.the trend was first increased then decreased with the grain size decreases.were studied by chemical analysis and solid-state13C nuclear magnetic resonance (NMR) technique.In general, humic acids (HA) from high-yield soils contained lower proportions of alkyl carbon and O-alkyl carbon whereas larger proportions of aromatic carbon and carbonyl carbon as compared with the control.The above results indicated that high-yield cultural operations can not only increase the contents of organic carbon, but also improve the quality of organic matter fraction in soil.2.The effects of short-term (two years) cropland management practices of high grain yield and high nutrient use efficiency of spring maize indicated that, The grain yield of maize ranging from8962to10827kg hm-2, increased in the order of farmers’practice<high grain yield and high nutrient use efficiency practice<higher grain yield and high nutrient use efficiency practice<higher grain yield practice. The difference among the farmers’practice, high grain yield and high nutrient use efficiency practice, and higher grain yield and high nutrient use efficiency practice treatments was statistically significant, but no significant difference was observed between the higher grain yield and high nutrient use efficiency practice and higher grain yield practice treatments, and nutrient use efficiency ranging from19.0to29.9g g-1, significantly increased in the order of higher grain yield practice<farmers’practice<higher grain yield and high nutrient use efficiency practice<high grain yield and high nutrient use efficiency practice.The above results indicated that a higher grain yield can be obtained by the adoption of recommended high-yield management practices compared with farmers’practice.The alkyl C/O-alkyl C ratio, increased in the order of high grain yield and high nutrient use efficiency practice<higher grain yield and high nutrient use efficiency practice<farmers’practice<higher grain yield practice,the results of the present study showed that the improvement in the nutrient use efficiency of applied fertilizers can increase both the quantity and quality of SOC in maize cropland ecosystems with high grain yield.3.The effects of the integrated adoption of several recommended sustainable agricultural practices (SAP) on maize grain yield and the quantitative and qualitative characteristics of soil organic carbon (SOC) were studied in a2-year, spring maize monoculture field plot experiment. The recommended agricultural practices included conservation tillage, combined application of organic manure and chemical fertilizers, and crop residue return. Compared with the conventional agricultural practices (CAP), the maize grain yield increased in the SAP treatment, and the difference between the two treatments was statistically significant (P<0.05) in the second season of the experiment (2010). The content of soil total organic carbon (TOC) and organic C fractions (i.e. water soluble organic C, easily oxidizable organic C, particulate organic C, humus C and black C) were higher in the SAP than in the CAP treatment, although the differences between the two treatments were not significant. The relative intensities of O-alkyl C and carbonyl C and the aliphatic C/aromatic C ratio were higher, while the relative intensities of alkyl C and aromatic C and the ratios of alkyl C/O-alkyl C and hydrophobic C/hydrophilic C were lower in solid-state13C CPMAS NMR spectra of HF-treated soils in the SAP than in the CAP treatment. The recommended sustainable agricultural practices were beneficial for the increase of maize grain yield and the improvement of the quantity and quality of SOC during a short-term period.4.Organic carbon functional groups in black soil using synchrotron radiation soft X-ray near-edge absorption spectroscopy (C-ls NEXAFS),Although different types of fertilizer, the processing is similar to the spectrum shape,there are four absorption peaks are concentrated in the range of285-290eV,followed in the285.3-285.5,287.4-287.7,288.8-288.9and290.7-290.9eV nearby,Compared with the control treatment, the aromatic C and the carboxyl C of soil increased, whereas the aliphatic C, the carbonyl C and the aliphatic C/aromatic C ratio decreased after the application of chemical fertilizer alone.compared with the no-fertilizer control treatment, the application of chemical fertilizers alone resulted in the relative proportion of aromatic compounds increased whereas that of aliphatic hydrocarbon compounds decreased. |
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