Effects Of Organic Fertilizer Substituting Mineral Nitrogen Fertilizer On Soil Carbon And Absorbed Nutrient In Spring Wheat

Too much nitrogen fertilizer could not increase crop yield.Instead,it loses a lot of nitrogen fertilizer,destroys water ecosystems,causes groundwater pollution and many other problems.Organic fertilizer is rich in a large number of elements,trace elements,plant growth regulators and other active substances needed for crop growth and development.Exploring the reasonable ratio of organic fertilizer to replace chemical nitrogen fertilizer is of great significance to black soil conservation and wheat growth and development.In this study,a field experiment was used and a total of 5 experimental treatments were set up:no fertilizer（CK）,organic fertilizer instead of100%chemical nitrogen fertilizer（M）,organic fertilizer substitute 50%chemical nitrogen fertilizer（M₁N₁）,organic fertilizer substitute 25%chemical nitrogen fertilizer（M₂N₂）and 100%chemical nitrogen fertilizer（N）,all fertilizers are used as base fertilizer and applied to the soil at one time to study the organic carbon and nitrogen content and sensitivity index of the cultivated soil（0-20 cm）during the process of planting spring wheat（SI）changes,soil soluble organic carbon composition and structural characteristics,different ratios of organic fertilizers instead of chemical nitrogen fertilizers will affect wheat（grains,straws,glumes）nutrient absorption,yield,nitrogen use efficiency,quality.Explore the substitution of organic fertilizers for chemical nitrogen fertilizers,the relationship between reduced fertilization technology,soil carbon components and nutrient absorption of spring wheat in northeast China provides a theoretical basis for seeking a reasonable range of organic fertilizers to replace chemical nitrogen fertilizers in spring wheat areas in northeast China.Research indicates:1.The soil SOC of the M treatment was the highest,which was 24.30 g·kg^-1.The TN content of the soil in the N treatment was significantly higher than other treatments,which was 2.70 g·kg^-1,and the M₂N₂treatment had the highest C/N value of 12.28;The contents of AN and AK in the treated soil were the highest,194.49 mg·kg^-1and 229.73 mg·kg^-1,respectively.The AP content in the soil treated with M was the highest,29.42 mg·kg^-1;the contents of POC,ROC and MBC in the soil were all organic fertilizers.Alternative chemical nitrogen fertilizer treatments（M₁N₁and M₂N₂treatments）were significantly higher than other treatments;M treatment soil DOC was significantly higher than other treatments,325.97 mg·kg^-1;soil organic carbon density components（L-LFOC,The content of O-LFOC,HFOC）was the highest in N treatment,followed by M treatment.The organic carbon content of each density component increased with the increase of the organic carbon content;soil POC（5.91%）,ROC（20.45%）,DOC（1.34%）,MBC（1.39%）and HFOC（91.14%）have the highest proportions in SOC,indicating that they have the highest activity under M2N2 treatment;among different measurement indicators,MBC has the highest SI value.It shows that the activated carbon component MBC in the soil reacts more sensitively,and MBC can be used as an indicator of early organic matter changes in this area.2.The three-dimensional fluorescence spectrum of soil DOC showed two characteristic fluorescence peaks of fulvic acid and humic acid;compared with CK treatment,the fluorescence structure of DOC in M₂N₂treatment soil was more excited than the fluorescence peaks of fulvic acid and humic acid.The blue shift of the emission wavelength and the increase in the integral percentage of the fluorescence area,the integral percentage of the fluorescenceⅠ,Ⅱ,andⅣareas are all significantly reduced;the FI₃₇₀of each treated soil DOC is distributed in the range of1.54～1.59,and the BIX range is 0.67-0.69,both It shows that the soil of each treatment has relative land biogenic characteristics;the HIX of the soil DOC of each treatment is less than 0.85,indicating the average degree of soil decay,while the HIX of M₂N₂treatment is 0.84,which is significantly higher than other treatments,indicating that M₂N₂treatment can increase the soil carbon storage:Parallel factor analysis identified 3 fluorescent components,which were divided into 2 humus-like components（fulvic acid-like substances and decay acid-like substances）and 1protein-like component（tyrosol-like）amino acid protein Substance);The total fluorescence intensity of soil DOC under the M treatment is the highest,with a higher relative concentration;the fluorescence intensity of the three components of the fertilization treatment is higher than that of the CK treatment,indicating that fertilization can increase the degree of soil decay,and reasonable organic fertilizer application chemical nitrogen fertilizers can increase the effectiveness of DOC and improve soil fertility;the relative proportion of the three organic components in soil DOC is the highest in C1,which is close to 50%,indicating that the proportion of small molecular substances in the soil in this area is low,and the degree of humification is low.3.Under the same quantification of nitrogen content,the chlorophyll content and LAI of wheat at the jointing stage were oriented from high to low.N treatment>organic-inorganic combined application treatment>M treatment;the wheat grain yield was the highest under N treatment,which was 4 414.06 kg·hm^-2,The M₂N₂treatment was followed by 4 410.17 kg·hm^-2;the wheat yield component index was the highest in the M₂N₂treatment,and the N treatment was the second.There was a very significant positive correlation between wheat yield and each yield component index（P<0.01）;wheat straw the total nutrient content of N,P,K₂O in slices and glumes was highest in N treatment,and the total nutrient content in wheat grain was highest in M₂N₂treatment;wheat absorbed nitrogen and apparent nitrogen fertilizer utilization were the highest in M₂N₂treatment,respectively 103.93 kg·hm^-2and 36.84%;the agronomic efficiency of nitrogen fertilizer is highest in N treatment,which is 31.11%,followed by M₂N₂treatment,which is 30.97%;wheat quality indicators（grain quality,flour quality,dough quality）are all treated with N to be the highest,reaching strong standard for medium gluten wheat,the grain quality of other treatments meets the quality requirements of medium gluten wheat.In summary,in the northeast spring wheat planting area,using organic fertilizer to replace chemical fertilizer by 0-25%can increase soil nutrient content,increase wheat yield and nitrogen fertilizer replacement,fertilize the soil and increase soil fertility levels while reducing excessive the soil excessively replaces the cationic effects of chemical fertilizers.