A method for reducing the emission of N2O stimulated by straw returning to field

Abstract

The present application relates to the field of farmland fertilization technology, and particularly relates to a method for reducing N2O emission stimulated by straw returning to field, wherein NPK (nitrogen, phosphorus and potassium) fertilizer and organic fertilizer are applied to the soil while the straw is returned to the field; the present application shows that the denitrification of the soil by the straw is enhanced by applying the organic fertilizer, so as to reduce the stimulating effect of the straw returning to the field on N2O emission, and thus the application of the organic fertilizer plays a key role in reducing the stimulating effect of the straw returning to the field on N2O emission in the agricultural ecosystem.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of farmland fertilization, in particular to a method for reducing N2O emission stimulated by straw returning. BACKGROUND

[0002] The two main microbial processes of soil nitrogen (N) in the biogeochemical cycle, nitrification and denitrification, account for most of the reaction processes of soil N2O emission. These processes are affected by the interaction of multiple factors, such as the availability of soil carbon (C) and nitrogen substrates, microbial community structure and function (such as extracellular enzyme activity), and soil aeration status. Generally, the supply of easily decomposable C and N substrates increased by fertilization or straw returning significantly promotes the production of soil N2O. The input of easily decomposable C not only serves as an energy source for nitrifying bacteria and denitrifying bacteria, but also creates an anaerobic environment by enhancing soil respiration, thereby enhancing N2O production. However, even abundant easily decomposable C can have a negative impact on N2O emission by simultaneously enhancing microbial immobilization of mineral nitrogen or N2O reduction to N2. The impact of straw addition on N2O emission can vary greatly under different conditions, with high C / N ratio (>40) possibly having a negative impact, and low C / N ratio (<15) possibly having a positive impact. The different responses of N2O emission to straw addition depend on the availability of mineral nitrogen, so the final impact of straw addition on N2O emission will be determined by the interaction of its inherent C and N content with the physical and chemical properties of the soil.

[0003] Some studies have shown that the combined application of organic fertilizer and straw is beneficial to the reduction of N2O emission, but some studies have shown that the combined application of organic fertilizer and straw promotes N2O emission, so this fertilization method is still controversial and needs further in-depth study. SUMMARY

[0004] In order to solve the above problems, the present application provides a method for reducing N2O emission stimulated by straw returning.

[0005] A method for reducing N2O emission stimulated by straw returning, wherein NPK chemical fertilizer and organic fertilizer are applied to the soil at the same time as straw returning.

[0006] Further, the application amount of the NPK chemical fertilizer includes N 250-400 kg / hm 2 , P2O5 80-150 kg / hm 2 , K2O 80-150 kg / hm 2 , the application amount of the organic fertilizer is 25,000-35,000 kg / hm 2 , and the amount of straw returning is 4,500-7,500 kg / hm 2 .

[0007] Description: Straw addition significantly stimulates N2O emission, while long-term application of NPK chemical fertilizer and organic fertilizer can reduce the positive effect of straw incorporation on N2O emission by enhancing denitrification after straw addition.

[0008] Further, the corresponding population abundance of nitrifying bacteria in the soil is adjusted to 5-10%.

[0009] Description: Reduce the content of denitrifying bacteria to reduce its stimulating effect on N2O emission.

[0010] Further, the soil C / N ratio is further adjusted to 25-30 according to the nature of the soil itself.

[0011] Description: The carbon-nitrogen ratio will affect the speed of the process of soil organic matter mineralization releasing C, N and other nutrient elements.

[0012] Further, the field water holding capacity is adjusted to 55-65%.

[0013] Description: After straw incorporation, straw needs to absorb a certain amount of water during its decomposition and microbial decomposition in the soil. Therefore, it is very important to regulate the field water holding capacity when incorporating straw.

[0014] Further, the organic fertilizer is any one of pig manure, chicken manure, cow manure and sheep manure; the straw is any one of corn straw, wheat straw, rice straw, peanut straw and sunflower straw.

[0015] Description: The above-mentioned organic fertilizer and straw are rich in nutrients and can improve the water and fertilizer retention performance of the soil and enhance the soil fertility.

[0016] Further, the straw is a straw powder, and the preparation method of the straw powder is:

[0017] The straw is first killed at 105°C for 25-30 min, then electron beam irradiation is performed after the killing is completed, the irradiation dose per 1 kg of straw is 0.4-0.5 kGy, then it is dried at 65-75°C to constant weight, and finally it is crushed to pass through a 0.2 mm sieve to obtain a straw powder.

[0018] Description: After killing, the enzyme activity in the straw is rapidly inhibited, avoiding excessive fermentation or deterioration of the straw in the natural environment due to the action of enzymes, which is conducive to maintaining the relative stability of the chemical composition of the straw. Electron beam irradiation after killing further destroys the complex organic structure of the straw, breaks the chemical bonds of the straw, and decomposes large molecular organic matter into small molecules, which are more easily decomposed and utilized by microorganisms in the soil, can accelerate the decomposition speed of the straw in the soil, make the nitrogen, phosphorus, potassium and other nutrients contained in the straw be released more quickly for plant absorption and utilization, and reduce the opportunity of nitrogen emission in the form of N2O.

[0019] Further, during the fixation process, 0.5-1% of the extract of Radix Morindae Officinlis by mass of the straw is added to the straw, and the preparation method of the extract of Radix Morindae Officinlis is as follows:

[0020] 1) The Radix Morindae Officinlis is first subjected to ice bath, the mass ratio of ice to Radix Morindae Officinlis is 1-5:1, and after standing for 5-10 min, the Radix Morindae Officinlis is crushed to obtain Radix Morindae Officinlis powder. The Radix Morindae Officinlis powder and a 20-30% KOH aqueous solution by mass are uniformly mixed at a solid-liquid ratio of 1g:35-40ml to obtain a mixed solution. The mixed solution is subjected to water bath treatment at 65-75℃ for 0.5-2h, and then solid-liquid separation is performed to obtain a supernatant;

[0021] 2) The supernatant obtained in step 1) and a Schizophyllum commune bacterial solution with a concentration of 1.5-2.0×10 8 cfu / ml are mixed at a volume ratio of 1:0.2-0.3 and subjected to ultrasonic extraction for 20-30 min to obtain an extract;

[0022] 3) The extract obtained in step 2) is concentrated under reduced pressure to 10-15 times the original concentration. The concentrated solution is adjusted to pH=4-5 by adding hydrochloric acid. Ethanol is added to the obtained filtrate in an amount of 2.5-3 times the volume of the filtrate to perform alcohol precipitation. The precipitate is freeze-dried to obtain the extract of Radix Morindae Officinlis.

[0023] Description: First, the Radix Morindae Officinlis is subjected to ice bath and crushing, which helps to destroy the plant cell structure and make the effective components in the cells more easily released. Then, the water bath treatment is performed. Under alkaline conditions and suitable temperature, some nitrogen-containing organic matter, phenols, flavonoids and other components in the Radix Morindae Officinlis can be better dissolved in the solution. These components have the effects of regulating soil microbial community and affecting the nitrogen transformation process, thereby reducing the generation of N2O. The supernatant is mixed with the Schizophyllum commune bacterial solution and subjected to ultrasonic extraction. Through the metabolic or enzymatic action of microorganisms, new substances are produced to make the denitrification process tend to generate nitrogen rather than N2O. The extract of Radix Morindae Officinlis contains some plant growth regulators and trace elements, etc., which further enrich the nutrient types, make the final soil nutrients more balanced, and meet the needs of plants at different growth stages, thereby reducing the nitrogen loss and N2O emission caused by nutrient deficiency or imbalance.

[0024] Further, the preparation method of the organic fertilizer is as follows:

[0025] The livestock and poultry manure, bran and urea are mixed at a mass ratio of 10:3:1-2, and then water is added to obtain compost materials with a water content of 50-55%. Then, 1.5-2wt% of EM fermentation agent is added to the compost materials, and aerobic fermentation is performed at 35-45℃ for 1-3d to obtain a manure fermentation product. The manure fermentation product is dried and crushed to obtain the organic fertilizer.

[0026] Description: The addition of bran to livestock and poultry manure can increase the carbon source, adjust the carbon-nitrogen ratio, and provide a more suitable nutrient environment for microorganisms to grow, which is conducive to the stability and transformation of nitrogen. The addition of urea supplements the nitrogen source, ensuring that there is enough nitrogen for microorganisms to utilize and subsequent plant absorption during the composting process. Through aerobic fermentation, some slow-release organic nitrogen compounds are formed. These slow-release nitrogen compounds gradually release in the soil, providing nitrogen for plants, avoiding the excessive nitrogen caused by one-time large-scale fertilization, and reducing the opportunity for nitrogen to be converted into N2O through denitrification and other processes.

[0027] Further, the method for returning the straw powder to the field is:

[0028] First, divide the soil into three layers from top to bottom, with the thickness of the three layers of soil being H1, H2, and H3, respectively, H1:H2:H3=4-5:3:2, and the soil porosity of each layer being TP i ;

[0029] Add straw powder to the three layers of soil in turn, wherein the amount of organic fertilizer added to each layer of soil is M, and the amount of straw powder added to each layer of soil is W i , M and W i are in kg / hm 2 , i is the number of layers, taking 1, 2, 3, M=9000-11000; W i =(M*TP i )*[H i / (H1+H2+H3)].

[0030] Description: The straw powder is added according to the specific ratio of the depth of each layer of soil. The oxygen content of the high layer of soil is relatively sufficient, and the addition of more straw can promote the growth and metabolism of beneficial microorganisms such as denitrifying bacteria, thereby reducing the emission of N2O, and the amount W i is determined by the porosity of each layer of soil, meeting the needs of microorganism growth and nitrogen transformation in different depth of soil, thereby more effectively regulating soil nitrogen cycle and reducing N2O emission.

[0031] Compared with the existing farmland fertilization method for reducing N2O emission, the beneficial effects of the present application are:

[0032] (1) The present application uses organic fertilizer, NPK fertilizer and straw together in farmland, because when adding straw alone, the straw strongly stimulates the N2O emission of all fertilized soils, mainly due to the increase of C / N availability and the increase of bacteria, fungi and norB gene abundance, while applying organic fertilizer can reduce the increase of N2O emission caused by straw returning to field by enhancing the complete denitrification of straw to soil, that is, the results of the present application show that the response degree of straw addition to N2O emission is affected by long-term fertilization measures, therefore, the application of organic fertilizer plays a key role in reducing the stimulating effect of straw returning to field on N2O emission in agricultural ecosystem, thereby reducing N2O emission during fertilization in farmland.

[0033] (2) The present application adds straw powder according to the specific proportion of the depth of each layer of soil, the oxygen content of high layer soil is relatively sufficient, and more straw can promote the growth and metabolism of beneficial microorganisms such as denitrifying bacteria, thereby reducing N2O emission, and the amount W is determined by the porosity of each layer of soil, meeting the needs of microorganism growth and nitrogen transformation in soil of different depths, thereby more effectively regulating soil nitrogen cycle and reducing N2O emission, and adding gnetum extract in straw, using plant growth regulators and trace elements in gnetum, further enriching the types of nutrients, making the final soil nutrients more balanced, meeting the needs of different growth stages of plants, reducing nitrogen loss and N2O emission caused by nutrient deficiency or imbalance. i BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the N2O emission data comparison chart of UQ and GZL under the fertilization method of the present application;

[0035] Figure 2 is the soil chemical property comparison chart of UQ and GZL under the fertilization method of the present application;

[0036] Figure 3 is the relative abundance comparison chart of bacteria of UQ and GZL under the fertilization method of the present application;

[0037] Figure 4 is the abundance comparison chart of nitrogen-related functional genes of UQ and GZL under the fertilization method of the present application;

[0038] Figure 5 is the PLS-PM analysis chart of the influence of soil chemical properties, soil microbial community and nitrogen-related functional genes on N2O emission;

[0039] Figure 6 is the relative abundance comparison chart of Bacteria and Fungi of UQ and GZL under the fertilization method of the present application;

[0040] Figure 7 ​is a beta diversity analysis chart of microorganisms;

[0041] Figure 8 is a relative abundance contrast chart of different bacteria and fungi of UQ and GZL under the fertilization method of the present application;

[0042] Figure 9 is a contrast chart of the results of the present application research 1;

[0043] Figure 10 is a contrast chart of the results of the present application research 2;

[0044] Figure 11 is a contrast chart of the results of the present application research 3;

[0045] Figure 12 is a contrast chart of the results of the present application research 4;

[0046] Figure 13 is a contrast chart of the results of the present application research 5. DETAILED DESCRIPTION

[0047] In order to further illustrate the manner of carrying out the present application and to further demonstrate the effects achieved by it, the technical solutions of the present application will be described in detail below with reference to experiments.

[0048] Example 1: A method for reducing the stimulation of N2O emission by straw returning, while returning straw to the field, NPK fertilizer and organic fertilizer are applied to the soil, the application amount of the NPK fertilizer includes N 325 kg / hm 2 , P2O5 115 kg / hm 2 , K2O 115 kg / hm 2 , and the application amount of the organic fertilizer (pig manure) is 30000 kg / hm 2 It can be understood that the application amount of the organic fertilizer here represents the application amount in dry weight, and the amount of straw returned to the field is 6000 kg / hm 2 ; further comprising adjusting the corresponding population abundance of nitrifying bacteria in the soil to be within 8% (the adjustment method is: when the corresponding population abundance is too small, adding nitrifying bacteria (such as nitric acid bacteria) to increase the corresponding population abundance of nitrifying bacteria, and when the corresponding population abundance is too large, adding nitrification inhibitors (such as DMPP) to reduce the corresponding population abundance of nitrifying bacteria); further adjusting the C / N ratio of the soil to 28 according to the nature of the soil itself, the adjustment method is: first test the C / N ratio of the soil itself, and then compare with the required C / N ratio, when the C / N ratio is too low, add carbon source (corn straw), and when the C / N ratio is too high, add nitrogen source (organic fertilizer); adjusting the field water holding capacity to 60%, the adjustment method is: first measure the field water holding capacity, if the field water holding capacity is too low, add water to the soil quantitatively; if the field water holding capacity is too high, drain the water;

[0049] The N in the NPK chemical fertilizer is from urea, P2O5 is from calcium superphosphate, and K2O is from potassium chloride;

[0050] The straw is straw powder, and a preparation method of the straw powder is as follows:

[0051] The corn straw is first killed at 105 DEG C for 28 min, then subjected to electron beam irradiation, the irradiation dose of each 1 kg of plant straw is 0.45 kGy, then dried at 70 DEG C to constant weight, and finally crushed to pass through a 0.2 mm sieve to obtain the straw powder.

[0052] Example 2: The difference between this example and Example 1 is that the application amount of the NPK chemical fertilizer comprises N 250 kg / hm 2 , P2O5 80 kg / hm 2 , K2O 150 kg / hm 2 , the application amount of the organic fertilizer is 35000 kg / hm 2 , and the straw returning amount is 4500 kg / hm 2 .

[0053] Example 3: The difference between this example and Example 1 is that the application amount of the NPK chemical fertilizer comprises N 400 kg / hm 2 , P2O5 150 kg / hm 2 , K2O 80 kg / hm 2 , the application amount of the organic fertilizer is 25000 kg / hm 2 , and the straw returning amount is 7500 kg / hm 2 .

[0054] Example 4: The difference between this example and Example 1 is that the corresponding population abundance of nitrifying bacteria in the soil is adjusted to be all 5%.

[0055] Example 5: The difference between this example and Example 1 is that the corresponding population abundance of nitrifying bacteria in the soil is adjusted to be all 10%.

[0056] Example 6: The difference between this example and Example 1 is that the soil C / N ratio is further adjusted to be 25.

[0057] Example 7: The difference between this example and Example 1 is that the soil C / N ratio is further adjusted to be 30.

[0058] Example 8: The difference between this example and Example 1 is that the field water holding capacity is adjusted to be 55%.

[0059] Example 9: The difference between this example and Example 1 is that the field water holding capacity is adjusted to be 65%.

[0060] Example 10: The difference between this example and Example 1 is that the organic fertilizer is chicken manure, and the peanut straw is first rolled at 105°C for 25 min.

[0061] Example 11: The difference between this example and Example 1 is that the organic fertilizer is cow manure, and the wheat straw is first rolled at 105°C for 30 min.

[0062] Example 12: The difference between this example and Example 1 is that the irradiation dose of each 1 kg of sunflower straw is 0.4 kGy.

[0063] Example 13: The difference between this example and Example 1 is that the irradiation dose of each 1 kg of sunflower straw is 0.5 kGy.

[0064] Example 14: The difference between this example and Example 1 is that drying is carried out at 65°C to constant weight, and finally crushing through a 0.2 mm sieve.

[0065] Example 15: The difference between this example and Example 1 is that drying is carried out at 75°C to constant weight, and finally crushing through a 0.2 mm sieve.

[0066] Example 16: The difference between this example and Example 1 is that the preparation method of the organic fertilizer is: mixing pig manure, bran and urea in a mass ratio of 10:3:1.5, then adding water to obtain compost material with a water content of 53%, then adding EM fermentation agent accounting for 1.8% of the compost material to the compost material, and carrying out aerobic fermentation at 40°C for 2d to obtain manure fermentation product and dry and crush to obtain the organic fertilizer.

[0067] Example 17: The difference between this example and Example 16 is that sheep manure, bran and urea are mixed in a mass ratio of 10:3:1, and then water is added to obtain compost material with a water content of 50%.

[0068] Example 18: The difference between this example and Example 16 is that chicken manure, bran, urea and moonseed extract are mixed in a mass ratio of 10:3:1:1, and then water is added to obtain compost material with a water content of 55%.

[0069] Example 19: The difference between this example and Example 16 is that EM fermentation agent accounting for 1.5% of the compost material is added to the compost material, and aerobic fermentation is carried out at 35°C for 1d.

[0070] Example 20: The difference between this example and Example 16 is that EM fermentation agent accounting for 2% of the compost material is added to the compost material, and aerobic fermentation is carried out at 45°C for 3d.

[0071] Example 21: The difference between this example and example 16 is that during the process of fixation, 0.5-1% of the extract of Radix Morindae Officinallis by mass of the straw is added to the straw, and the preparation method of the extract of Radix Morindae Officinallis is as follows:

[0072] 1) First, the Radix Morindae Officinallis is subjected to ice bath, the mass ratio of ice to Radix Morindae Officinallis is 3:1, and after standing for 8 min, the Radix Morindae Officinallis is crushed to obtain Radix Morindae Officinallis powder. The Radix Morindae Officinallis powder and 25% KOH aqueous solution by mass fraction are uniformly mixed at a solid-liquid ratio of 1g:38ml to obtain a mixed solution, and the mixed solution is treated in a water bath at 70°C for 1h, and then solid-liquid separation is performed to obtain a supernatant;

[0073] 2) The supernatant obtained in step 1) and the Schizophyllum commune liquid with a concentration of 1.5-2.0x10 8 cfu / ml are mixed at a volume ratio of 1:0.25 and subjected to ultrasonic extraction for 25 min, the ultrasonic power is 290W, the ultrasonic frequency is 70kHz, and the ultrasonic treatment temperature is 30°C, to obtain an extract;

[0074] 3) The extract obtained in step 2) is concentrated under reduced pressure to 12 times the original concentration, and the concentrated solution is added with 37% hydrochloric acid by mass fraction to adjust the pH to 4.5. The filtrate obtained by filtering under a filter diameter of 10μm is added with ethanol in an amount of 2.8 times the volume of the filtrate to perform alcohol precipitation, and the precipitate is freeze-dried at-60°C to obtain the extract of Radix Morindae Officinallis.

[0075] Example 22: The difference between this example and example 21 is that the mass ratio of ice to Radix Morindae Officinallis is 1:1, standing for 5 min, the Radix Morindae Officinallis powder and 20% KOH electrolytic water by mass fraction are uniformly mixed at a solid-liquid ratio of 1g:35ml to obtain a mixed solution, and the mixed solution is treated in a water bath at 65°C for 0.5h.

[0076] Example 23: The difference between this example and example 21 is that the mass ratio of ice to Radix Morindae Officinallis is 5:1, standing for 10 min, the Radix Morindae Officinallis powder and 30% KOH electrolytic water by mass fraction are uniformly mixed at a solid-liquid ratio of 1g:40ml to obtain a mixed solution, and the mixed solution is treated in a water bath at 75°C for 2h.

[0077] Example 24: The difference between this example and example 21 is that the supernatant and the Schizophyllum commune liquid with a concentration of 1.5x10 8 cfu / ml are mixed at a volume ratio of 1:0.2 and subjected to ultrasonic extraction for 20 min.

[0078] Example 25: The difference between this example and example 21 is that the supernatant and the Schizophyllum commune liquid with a concentration of 2.0x10 8 cfu / ml are mixed at a volume ratio of 1:0.3 and subjected to ultrasonic extraction for 30 min.

[0079] Example 26: The difference between this example and Example 21 is that the extract is concentrated under reduced pressure to 10 times the original concentration, the concentrated solution is added with hydrochloric acid to adjust the pH to 4, and the filtrate obtained is filtered, and then 3 times the volume of ethanol is added to the filtrate to precipitate the alcohol.

[0080] Example 27: The difference between this example and Example 21 is that the extract is concentrated under reduced pressure to 15 times the original concentration, the concentrated solution is added with hydrochloric acid to adjust the pH to 5, and the filtrate obtained is filtered, and then 2.5 times the volume of ethanol is added to the filtrate to precipitate the alcohol.

[0081] Example 28: The difference between this example and Example 21 is that the method of returning the straw powder to the soil is:

[0082] The soil is first divided into three layers from top to bottom, and the thickness of the three layers of soil is H1, H2, and H3, respectively, H1:H2:H3=4.5:3:2, and the soil porosity of each layer of soil is TP i , the TP i of the H1-thickness layer of soil is 65%, the TP i of the H2-thickness layer of soil is 50%, and the TP i of the H3-thickness layer of soil is 30%;

[0083] The straw powder is added to the three layers of soil in turn, wherein the amount of organic fertilizer added to each layer of soil is M, and the amount of straw powder added to each layer of soil is W i , the units of M and W i are kg / hm 2 , i is the number of layers, which is 1, 2, or 3, M=10000; W i =(M×TP i )×[H i / (H1+H2+H3)], i.e., W1=3078, W2=1578, and W3=631.

[0084] Example 29: The difference between this example and Example 28 is that H1:H2:H3=4:3:2.

[0085] Example 30: The difference between this example and Example 28 is that H1:H2:H3=5:3:2.

[0086] Example 31: The difference between this example and Example 28 is that M=9000.

[0087] Example 32: The difference between this example and Example 28 is that M=11000.

[0088] Experimental Example: The description of this experimental example is based on the description of the scheme in Example 1, and is intended to illustrate the actual application effect of the present application.

[0089] Experimental design: In order to illustrate the stimulating effect of reducing N2O emission by applying organic fertilizer and straw in combination in the present application, the following experimental groups were made with Urumqi soil (UQ) and Gongzhuling soil (GZL) in the present application, and the soil treatment parameters in Example 1 were taken as the benchmark as the control;

[0090] Control Example 1: No fertilizer (CK);

[0091] Control Example 2: Apply NPK chemical fertilizer (NPK);

[0092] Control Example 3: Apply straw and NPK chemical fertilizer (NPKS);

[0093] Control Example 4: Apply organic fertilizer and NPK chemical fertilizer (NPKM);

[0094] The straw powder applied in the present application was labeled, and the labeled straw powder was added to Control Examples 1-4. The addition of labeled straw powder in Control Example 4 is Example 1 of the present application. The cumulative N2O emission and the effect of straw addition on N2O emission of the four long-term fertilization soils (CK; NPK; NPKS; NPKM) under the condition of adding and not adding straw were analyzed, and the results are shown in Figures 1-4

[0095] Figure 1 It is shown that during the 180-day incubation period, the N2O emission rate of Urumqi soil (UQ, Figure 1 a), Gongzhuling soil (GZL, Figure 1 b), and the cumulative N2O emission (c) and the effect of straw addition on N2O emission (d) of the four long-term fertilization soils (CK; NPK; NPKS; NPKM) under the condition of adding and not adding straw; Figure 1 Figure 1 Figure 1 aand 1b). The effect of straw addition on N2O emission is strongly dependent on the fertilization practice (c). Under all fertilization and straw addition treatments, the N2O emission of GZL soil is increased by an average of 83% (c) compared to UQ soil. Without straw, fertilization significantly increases N2O emission by 22-168% compared to the CK treatment, except for the NPKS treatment under GZL soil. After straw addition, N2O emission is increased by 11-50% under the NPKM treatment and by 94-141% under the CK treatment compared to the corresponding treatment without straw (d); Figure 1 Figure 1 Figure 1

[0096] Figure 2 ​​​​​​Soil chemical properties of four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition during 180 days incubation were presented; long-term fertilization and straw addition significantly affected soil nutrient availability Figure 2 ). NH4 + -N and DOC contents were higher in UQ soils than in GZL soils, but NO3 – -N content was lower in UQ soils than in GZL soils Figure 2 . Compared with CK treatment, NPKM treatment significantly increased NH4 + -N, NO3 – -N, DOC and DON contents in UQ and GZL soils, except for NH4 + -N in GZL soils Figure 2 . Straw addition significantly increased NH4 + -N content in CK, NPK and NPKM treatments in UQ soils, but only in NPKS treatment in GZL soils with straw addition Figure 2 a). Straw addition significantly increased NO3 – -N content in CK and NPK treatments by 55-77% and 25-40%, respectively, compared with treatments without straw addition Figure 2 b). Straw addition significantly increased DOC content in all fertilized treatments, except for NPK treatment in GZL soils, by 18-106% compared with treatments without straw addition Figure 2 c). Straw addition significantly decreased DON content in NPK and NPKS treatments by 17-21% and 10-18%, respectively, compared with treatments without straw addition Figure 2 d;

[0097] Figure 3 Relative abundances of Anaerolineae (a) and Eurotiomycetes (b) in four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition during 180 days incubation were presented; fertilization and straw addition significantly changed soil microbial community composition Figures 6-8 ; Figure 3 PCoA analysis showed a clear separation between bacterial and fungal compositions among fertilization and straw addition treatments Figure 7 . Notably, fertilization (47-91%) explained more variation in bacterial and fungal community composition than straw addition (3-16%) Figure 7). At the class level, fertilization (NPK, NPKS and NPKM treatments; 0.4-3.8%) significantly decreased Anaerolineae relative abundance in UQ and GZL soils compared to CK treatment (2.4-4.2%) ( Figure 3 a). Straw addition significantly increased Eurotiomycetes relative abundance in CK, NPKS and NPKM treatments in UQ soil by 27%, 23% and 53%, respectively, compared to the corresponding treatments without straw addition ( Figure 3 b). RF analysis indicated that Anaerolineae bacteria and Eurotiomycetes fungi were important microbial groups regulating N2O emission ( Figure 3 c). Regression analysis further revealed that N2O emission was significantly negatively correlated with Anaerolineae relative abundance (R 2 = 0.53, p < 0.001) and significantly positively correlated with Eurotiomycetes relative abundance (R 2 = 0.35, p < 0.001) ( Figure 3 d and 3e);

[0098] Figure 4 The abundance of nitrogen-related functional genes in four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition during the 180-day incubation period is shown; Microbial nitrogen-related functional genes were strongly affected by fertilization and straw addition. Compared to CK treatment, amoA and hao abundance in NPKM treatment was significantly reduced by 22-60% and 22-31%, respectively, while amoB abundance showed no statistical difference ( Figure 4 a-c). Compared to CK treatment, nirK and nosZ gene abundance in NPKM treatment was significantly reduced by 6-7% and 1-10%, respectively, while narG and norB gene abundance was significantly increased by 19-25% and 28-59%, respectively ( Figure 4 d-g). In all fertilized treatments, straw addition significantly reduced amoA, amoB, hao and nirK gene abundance compared to the treatment without straw addition, while increased narG, norB and nosZ gene abundance;

[0099] Figure 5 The correlations between N2O emission, soil chemical properties, soil microbial community and nitrogen-related functional genes are shown Figure 5 a). PLS-PM analysis was used to investigate the specific effects of soil chemical properties, soil microbial community and nitrogen-related functional genes on N2O emission Figure 5b). Values are path coefficients; arrow width is proportional to the magnitude of the path coefficient. Solid and dashed lines indicate positive and negative correlations, respectively. *, **, *** indicate significant levels of p < 0.05, p < 0.01 and p < 0.001, respectively. The results showed that soil N2O emission was positively correlated with NO3 – -N, DON, norB, amoA and amoB were significantly positively correlated, but NH4 + -N, DOC / NO3 – -N and nosZ were significantly negatively correlated Figure 5 a). PLS-PM analysis showed that soil nutrients directly affected N2O emission by changing microbial community composition and nitrogen-related functional genes Figure 5 b). Nitrifying genes (amoA and amoB abundance) showed a direct negative effect on N2O emission (-0.25), while denitrifying genes (nirK, norB and nosZ abundance) showed a direct positive effect on N2O emission (+0.51) Figure 5 b and Figure 5 c);

[0100] From the above results, it can be seen that under all fertilization and straw addition treatments, the N2O emission of GZL soil is higher than that of UQ soil. Straw addition strongly stimulates the N2O emission of all fertilized soils, mainly due to the increase in C / N availability and the increase in the abundance of bacteria, fungi and norB genes. Under the CK treatment, straw addition significantly stimulates N2O emission, while long-term fertilization reduces the stimulating effect of N2O emission. Fertilization reduces the positive impact of straw addition on N2O emission by enhancing the complete denitrification after straw addition. These results show that the response degree of straw addition to N2O emission is affected by long-term fertilization measures. The present application highlights the key role of fertilization, especially organic fertilizer application, in reducing the stimulating effect of straw return on N2O emission in agricultural ecosystems.

[0101] Correlation performance experiment: compare the actual performance of the present application under different experimental conditions, compare the N2O emission of each example with example 1, and explore the increase or decrease amplitude of N2O emission of each example compared with example 1, the specific data are shown below.

[0102] 1. To explore the effect of the fertilization parameters and straw return parameters of the present application on N2O emission.

[0103] From Figure 9 It can be seen that compared with examples 1-9, the addition ratio of straw and fertilizer is too small or too large, the content of nitrifying bacteria is too small or too large, the C / N ratio in soil is too small or too large, and the field water holding capacity is too small or too large, which can increase the N2O emission rate, therefore, the parameter effect of example 1 is relatively better in comprehensive comparison.

[0104] 2. Explore the effect of straw preparation parameters of the application on N2O emission.

[0105] The difference between Comparative Example 5 and Example 1 is that the straw is not subjected to electron beam irradiation treatment;

[0106] From Figure 10 As can be seen from the results, Comparative Example 5 has a lower microbial decomposition and utilization efficiency than Examples 1, 10-15 due to the lack of electron beam irradiation treatment on the straw, thus indicating that the fixation and electron beam irradiation treatment of the straw can effectively reduce the N2O emission rate;

[0107] As can be seen from the comparison between Comparative Example 1 and Examples 10-15, too small or too large fixation parameters, too small or too large irradiation parameters, and too small or too large drying and crushing parameters can all increase the N2O emission rate, thus the parameters of Example 1 are relatively more optimal in terms of comprehensive comparison.

[0108] 3. Explore the effect of organic fertilizer preparation parameters of the application on N2O emission.

[0109] From Figure 11 As can be seen from the results, the mixture of poultry manure and bran, EM microbial agent, etc. has a better effect on reducing the N2O emission rate than ordinary poultry manure;

[0110] As can be seen from the comparison between Comparative Example 1 and Examples 16-20, too small or too large proportion of poultry manure and too small or too large aerobic fermentation parameters of the fermentation microbial agent can all increase the N2O emission rate, thus the parameters of Example 16 are relatively more optimal in terms of comprehensive comparison.

[0111] 4. Explore the effect of adding Radix Ampelopsis extract to the straw on N2O emission.

[0112] The difference between Comparative Example 6 and Example 21 is that the Radix Ampelopsis extract does not contain Schizophyllum commune;

[0113] From Figure 12 As can be seen from the results, after adding the Radix Ampelopsis extract to the straw, the soil is provided with regulating substances and trace elements, thereby reducing nitrogen loss and N2O emission, and significantly reducing the N2O emission rate compared with Example 1; Comparative Example 6 has a significant increase in the N2O emission rate due to the lack of Schizophyllum commune in the Radix Ampelopsis extract, which reduces the metabolic and enzymatic effects of microorganisms compared with Examples 21-27;

[0114] As can be seen from the comparison between Comparative Example 21 and Examples 21-27, too small or too large ice bath treatment parameters of Radix Ampelopsis, too small or too large proportion of Schizophyllum commune microbial solution, and too small or too large alcohol precipitation parameters can all increase the N2O emission, thus the parameters of Example 21 are relatively more optimal in terms of comprehensive comparison.

[0115] 5. To explore the effect of adding straw and organic fertilizer on N2O emission in different soil depths.

[0116] Comparative Example 7 is different from Example 28 in that the amount of straw powder added in each layer of soil is the same.

[0117] From Figure 13 As can be seen from the results, in Comparative Example 7, the amount of straw powder added in each layer of soil is the same, and thus there is a lack of a comparison of the nutrients required by each layer of soil, which cannot meet the needs of nitrogen conversion in different depths of soil, resulting in a significant increase in the N2O emission rate compared to Examples 28-32.

[0118] As can be seen from Comparative Examples 21, 28-32, adding straw powder according to the specific proportion of each layer of soil depth can promote the growth and metabolism of beneficial microorganisms such as denitrifying bacteria, thereby reducing N2O emission, and further reducing the N2O emission rate compared to Example 21.

[0119] As can be seen from Comparative Examples 28-32, too small or too large a difference in the depth of each layer of soil, or too small or too large an amount of straw powder added in each layer, can increase the N2O emission rate. Therefore, in terms of comprehensive comparison, the parameters of Example 28 are relatively more optimal.

Claims

1. A method for reducing N2O emissions stimulated by straw returning to the field, characterized in that, While returning straw to the field, NPK fertilizer and organic fertilizer are applied to the soil; The straw used in the straw return to the field is straw powder, and the method for preparing the straw powder is as follows: The straw is first blanched at 105℃ for 25-30 minutes. After blanching, it is irradiated with an electron beam with an irradiation dose of 0.4-0.5 kGy per kg of straw. Then it is dried at 65-75℃ to constant weight and finally crushed through a 0.2 mm sieve to obtain straw powder. During the blanching process, 0.5-1% by weight of Polygonum multiflorum extract is added to the straw. The preparation method of Polygonum multiflorum extract is as follows: 1) First, put the Polygonum multiflorum in an ice bath with a mass ratio of ice to Polygonum multiflorum of 1~5:

1. After standing for 5~10 minutes, crush it to obtain Polygonum multiflorum powder. Mix the Polygonum multiflorum powder with a KOH aqueous solution of 20~30% by mass at a solid-liquid ratio of 1 g: 35~40 ml to obtain a mixed solution. Treat the mixed solution in a water bath at 65~75℃ for 0.5~2 h, and then separate the solid and liquid to obtain the supernatant. 2) Combine the supernatant obtained in step 1) with a concentration of 1.5~2.0×10 8 The cfu / ml Schizophyllum commune culture was mixed at a volume ratio of 1:0.2~0.3 and ultrasonically extracted for 20~30 min to obtain the extract; 3) Concentrate the extract obtained in step 2) under reduced pressure to 10 to 15 times the original concentration. Adjust the pH of the concentrate to 4 to 5 with hydrochloric acid. Add 2.5 to 3 times the volume of ethanol to the filtrate for alcohol precipitation. Freeze-dry the precipitate to obtain the extract of Polygonum multiflorum. The method for returning straw to the field is as follows: First, the soil is divided into three layers from top to bottom, with thicknesses H1, H2, and H3 respectively. The ratio of H1:H2:H3 is 4~5:3:2, and the porosity of each soil layer is TP. i ; Straw powder was added to three soil layers sequentially. The amount of organic fertilizer added to each soil layer was M, and the amount of straw powder added to each soil layer was W. i M and W i The unit is kg / hm 2 i represents the layer number, which can be 1, 2, or 3; M = 9000~11000; W i =(M×TP i )×[H i / (H1+H2+H3)].

2. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, The application rate of the NPK fertilizer includes 250~400 kg / hm² of N. 2 P2O5 80~150 kg / hm 2 K2O 80~150 kg / hm 2 The application rate of organic fertilizer is 25,000~35,000 kg / hm. 2 The amount of straw returned to the field is 4500~7500 kg / hm. 2 .

3. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, It also includes adjusting the corresponding population abundance of nitrifying bacteria in the soil to 5-10%.

4. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, It also includes further adjusting the soil C / N ratio to 25-30 based on the soil's own properties.

5. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, This also includes regulating field water holding capacity to 55-65%.

6. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, The organic fertilizer is any one of pig manure, chicken manure, cow manure, and sheep manure; the straw is any one of corn straw, wheat straw, rice straw, peanut straw, and sunflower straw.

7. The method for reducing N2O emissions stimulated by straw returning to the field as described in claim 1, characterized in that, The method for preparing the organic fertilizer is as follows: Animal manure, bran, and urea are mixed in a mass ratio of 10:3:1~2, and water is added to obtain compost material with a moisture content of 50~55%. Then, 1.5~2 wt% of EM fermentation agent is added to the compost material and aerobic fermentation is carried out at 35~45℃ for 1~3 days to obtain manure fermentation products, which are then dried and crushed to obtain organic fertilizer.

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