Method for reducing N2O emission stimulated by straw returning to field

Abstract

The invention relates to the technical field of farmland fertilization, in particular to a method for reducing N2O emission stimulated by straw returning, which comprises the following steps: applying NPK (Nitrogen, Phosphorus and Potassium) chemical fertilizer and organic fertilizer into soil while straw returning; the invention shows that the denitrification effect of the straws on the soil is enhanced by applying the organic fertilizer so as to reduce the excitation effect of the straw returning to the field on the N2O emission, so that the application of the organic fertilizer plays a key role in reducing the excitation effect of the straw returning to the field in an agricultural ecosystem on the N2O emission.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland fertilization, and in particular to a method for reducing N2O emissions stimulated by returning straw to fields. Background Art

[0002] Two major microbial processes in the soil nitrogen (N) biogeochemical cycle—nitrification and denitrification—account for the majority of soil NO emissions. These processes are influenced by the interplay of multiple factors, including soil carbon (C) and nitrogen substrate availability, microbial community structure and function (e.g., extracellular enzyme activity), and soil aeration. Generally, an increased supply of readily degradable C and N substrates, such as through fertilization or straw incorporation, significantly promotes soil NO production. Labile C input not only serves as an energy source for nitrifying and denitrifying bacteria but also enhances NO production by creating an anaerobic environment through enhanced soil respiration. However, even abundant labile C can negatively impact NO emissions by simultaneously enhancing microbial fixation of mineral nitrogen or NO reduction to N. The effects of straw addition on NO emissions can vary significantly across different conditions, with high C / N ratios (>40) potentially having a negative impact and low C / N ratios (≤15) potentially having a positive effect. N2O emissions responded differently to straw addition depending on the availability of mineral nitrogen, so the ultimate effect of straw addition on N2O emissions will be determined by the interaction between its intrinsic C and N contents and soil physicochemical properties.

[0003] Some studies have shown that the combined application of organic fertilizer and straw is beneficial to reducing N2O emissions, but some studies have also shown that the combined application of organic fertilizer and straw promotes N2O emissions. This fertilization method is still controversial and requires further in-depth research. Summary of the Invention

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

[0005] A method for reducing N2O emissions stimulated by returning straw to the field comprises applying NPK fertilizer and organic fertilizer to the soil while returning the straw to the field.

[0006] Furthermore, the amount of NPK fertilizer applied includes N 250-400 kg / hm 2 、P2O5 80~150kg / hm 2 、K2O80~150kg / hm 2 , the application rate of organic fertilizer is 25000~35000kg / hm 2 The amount of straw returned to the field is 4500~7500kg / hm 2 .

[0007] Note: Straw addition significantly stimulates N2O emissions, while long-term application of NPK fertilizers and organic fertilizers can mitigate the positive impact of straw return on N2O emissions by enhancing denitrification after straw addition.

[0008] Furthermore, it also includes adjusting the corresponding population abundance of nitrifying bacteria in the soil to 5-10%.

[0009] Note: Reduce the content of denitrifying bacteria to reduce their stimulation of N2O emissions.

[0010] Furthermore, it also includes further adjusting the soil C / N ratio to 25-30 according to the properties of the soil itself.

[0011] Note: The carbon-nitrogen ratio will affect the speed of the process of mineralization of soil organic matter and release of nutrients such as C and N.

[0012] Furthermore, it also includes regulating the field water holding capacity to 55-65%.

[0013] Note: After returning straw to the field, it absorbs a certain amount of water during the process of decay and microbial decomposition in the soil. Therefore, it is very important to control the field water holding capacity when returning straw to the field.

[0014] Furthermore, 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] Note: The above organic fertilizers and straw are rich in nutrients and can improve the soil's water and fertilizer retention capabilities and enhance soil fertilizer efficiency.

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

[0017] The straw was first fixed at 105°C for 25-30 minutes, and then irradiated with electron beams at a dose of 0.4-0.5 kGy per kg of straw. The straw was then dried at 65-75°C to a constant weight, and finally pulverized and passed through a 0.2 mm sieve to obtain straw powder.

[0018] Description: After the withering treatment, the enzyme activity in the straw is rapidly suppressed, preventing the straw from excessive fermentation or deterioration due to enzyme action in the natural environment, which helps maintain the relative stability of the straw's chemical composition. Electron beam irradiation after withering further destroys the straw's complex organic structure, breaking the straw's chemical bonds and breaking down large organic molecules into small molecules, which are more easily decomposed and utilized by microorganisms in the soil. This can accelerate the decomposition of straw in the soil, releasing nutrients such as nitrogen, phosphorus, and potassium more quickly for plant absorption and utilization, and reducing the chance of nitrogen emissions in the form of N2O.

[0019] Furthermore, during the fixing process, 0.5-1% of the mass of the tuberculiae ternatea extract is added to the straw, and the preparation method of the tuberculiae ternatea extract is as follows:

[0020] 1) first placing the tuberculinum sibiricum in an ice bath with a mass ratio of ice to tuberculinum sibiricum of 1-5:1, letting it stand for 5-10 minutes, then crushing it to obtain tuberculinum sibiricum powder, and uniformly mixing the tuberculinum sibiricum powder with a 20-30% by mass KOH aqueous solution at a solid-liquid ratio of 1 g:35-40 ml to obtain a mixed solution, treating the mixed solution in a water bath at 65-75°C for 0.5-2 hours, and performing solid-liquid separation to obtain a supernatant;

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

[0022] 3) The extract obtained in step 2) is concentrated under reduced pressure to 10 to 15 times the original concentration, the concentrated solution is adjusted to pH 4 to 5 by adding hydrochloric acid, and the filtrate obtained by filtration is added with ethanol in an amount of 2.5 to 3 times the volume of the filtrate for alcohol precipitation to obtain a precipitate, which is freeze-dried to obtain a Polygonum multiflorum extract.

[0023] Description: First, the Polygonum multiflorum is crushed in an ice bath to help destroy the plant cell structure and make the effective ingredients in the cells more easily released. Then it is treated in a water bath. Under alkaline conditions and suitable temperature, some nitrogen-containing organic matter, phenols, flavonoids and other components in the Polygonum multiflorum can be better dissolved in the solution. These components have the function of regulating soil microbial communities and affecting the nitrogen conversion process, thereby reducing the generation of N2O. The supernatant is mixed with the Schizophyllum bacterial liquid and ultrasonically extracted. Through microbial metabolism or enzymatic hydrolysis, new substances are produced, making the denitrification process more inclined to produce nitrogen gas rather than N2O. The Polygonum multiflorum extract contains some plant growth regulators and trace elements, which further enrich the types of nutrients, making the final soil nutrients more balanced, which can meet the needs of plants at different growth stages and reduce nitrogen loss and N2O emissions caused by nutrient deficiency or imbalance.

[0024] Furthermore, the preparation method of the organic fertilizer is:

[0025] The method comprises mixing livestock and poultry manure, bran and urea in a mass ratio of 10:3:1-2, adding water to obtain a compost material with a water content of 50-55%, adding an EM fermentation agent accounting for 1.5-2 wt% of the compost material to the compost material, and aerobically fermenting the compost material at 35-45° C. for 1-3 days to obtain a manure fermentation product, which is dried and crushed to obtain an organic fertilizer.

[0026] Description: Adding bran to livestock and poultry manure increases the carbon source, adjusts the carbon-nitrogen ratio, and creates a more favorable nutritional environment for microbial activity, which promotes nitrogen stabilization and conversion. The addition of urea supplements the nitrogen source, ensuring sufficient nitrogen for microbial utilization during the composting process and subsequent plant uptake. Aerobic fermentation forms slow-release organic nitrogen compounds. These slow-release nitrogen compounds are gradually released into the soil, continuously providing nitrogen to plants, avoiding nitrogen overload caused by a single, large-scale fertilization. This reduces the chance of nitrogen conversion to N2O through processes such as denitrification.

[0027] Furthermore, the method of returning the straw powder to the field is:

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

[0029] Add straw powder to the three layers of soil in sequence, where 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 The unit is kg / hm 2 , i is the number of layers, 1, 2, 3, M = 9000 ~ 11000; W i =(M×TP i )×[H i / (H1+H2+H3)].

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

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

[0032] (1) The present invention applies organic fertilizer, NPK fertilizer and straw to farmland together. When straw is added alone, it strongly stimulates N2O emissions from all fertilized soils, mainly due to the increase in C / N availability and the increase in the abundance of bacteria, fungi and norB genes. Organic fertilizer application reduces the increase in N2O emissions caused by straw return to the field by enhancing the complete denitrification effect of straw on the soil. That is, the results of the present invention show that the response degree of straw addition to N2O emissions is affected by long-term fertilization measures. Therefore, the application of organic fertilizer plays a key role in reducing the stimulating effect of straw return on N2O emissions in agricultural ecosystems, thereby reducing N2O emissions during farmland fertilization.

[0033] (2) The present invention adds straw powder according to a specific ratio of each soil depth. The oxygen content in the upper soil is relatively sufficient. Adding more straw can promote the growth and metabolism of beneficial microorganisms such as denitrifying bacteria, thereby reducing N2O emissions. The addition amount W is determined by the porosity of each soil layer. i , meeting the needs of soil microbial growth and nitrogen conversion at different depths, thereby more effectively regulating soil nitrogen cycle and reducing N2O emissions. By adding Sophora flavescens extract to the straw and utilizing the plant growth regulators and trace elements in Sophora flavescens, the nutrient types are further enriched, making the final soil nutrients more balanced, meeting the needs of plants at different growth stages, and reducing nitrogen loss and N2O emissions due to nutrient deficiency or imbalance. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 2 It is a comparison chart of soil chemical properties of UQ and GZL under the fertilization method of the present invention;

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

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

[0038] Figure 5 This is a PLS-PM analysis of the effects of soil chemical properties, soil microbial communities, and nitrogen-related functional genes on N2O emissions;

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

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

[0041] Figure 8 is a comparison of the relative abundance of different bacteria and fungi in UQ and GZL under the fertilization method of the present invention;

[0042] Figure 9 This is a comparison chart of the results of the present invention's exploration 1;

[0043] Figure 10 This is a comparison chart of the results of the present invention's exploration 2;

[0044] Figure 11 This is a comparison chart of the results of the present invention's exploration 3;

[0045] Figure 12 This is a comparison chart of the results of the present invention's exploration 4;

[0046] Figure 13 It is a comparison chart of the results of exploration 5 of the present invention. DETAILED DESCRIPTION

[0047] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0048] Example 1: A method for reducing N2O emissions stimulated by returning straw to the field, wherein NPK fertilizer and organic fertilizer are applied to the soil at the same time as returning straw to the field, wherein the amount of NPK fertilizer applied includes N 325kg / hm 2 、P2O5 115kg / hm 2 、K2O 115kg / hm 2 , the amount of organic fertilizer (pig manure) applied is 30,000 kg / hm 2 It is understandable that the amount of organic fertilizer applied here refers to the amount applied based on the dry weight of organic fertilizer, and the amount of straw returned to the field is 6000kg / hm 2 ; Also included is adjusting the corresponding population abundance of nitrifying bacteria in the soil to 8% (the adjustment method is: when the corresponding population abundance is too low, nitrifying bacteria (such as nitrate bacteria) are added to increase the corresponding population abundance of nitrifying bacteria; when the corresponding population abundance is too high, nitrification inhibitors (such as DMPP) are added to reduce the corresponding population abundance of nitrifying bacteria); further adjusting the soil C / N ratio to 28 according to the properties of the soil itself, the adjustment method is: first test the soil's own C / N ratio, and then compare it with the desired C / N ratio. When the C / N ratio is too low, a carbon source (corn straw) is added; when the C / N ratio is too high, a nitrogen source (organic fertilizer) is added; regulating the field water holding capacity to 60%, the adjustment method is: first determine the field water holding capacity, if the field water holding capacity is too low, add water to the soil in a quantitative manner; if the field water holding capacity is too high, drain the soil;

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

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

[0051] The corn stalks were first sterilized at 105°C for 28 minutes, and then irradiated with electron beams at a dose of 0.45 kGy per kg of plant stalks. The stalks were then dried at 70°C to a constant weight and finally pulverized to pass through a 0.2 mm sieve to obtain straw powder.

[0052] Example 2: This example is different from Example 1 in that the amount of NPK fertilizer applied includes N 250kg / hm 2 、P2O5 80kg / hm 2 、K2O 150kg / hm 2 , the application rate of organic fertilizer is 35000kg / hm 2 , the amount of straw returned to the field is 4500kg / hm 2 .

[0053] Example 3: This example is different from Example 1 in that the amount of NPK fertilizer applied includes N 400kg / hm 2 、P2O5 150kg / hm 2 、K2O 80kg / hm 2 , the amount of organic fertilizer applied is 25000kg / hm 2 , the amount of straw returned to the field is 7500kg / hm 2 .

[0054] Example 4: This example differs from Example 1 in that the corresponding population abundance of nitrifying bacteria in the soil is adjusted to 5%.

[0055] Example 5: This example differs from Example 1 in that the corresponding population abundance of nitrifying bacteria in the soil is adjusted to 10%.

[0056] Example 6: This example differs from Example 1 in that the soil C / N ratio is further adjusted to 25.

[0057] Example 7: This example differs from Example 1 in that the soil C / N ratio is further adjusted to 30.

[0058] Example 8: This example differs from Example 1 in that the field capacity is regulated to 55%.

[0059] Example 9: This example differs from Example 1 in that the field capacity is regulated to 65%.

[0060] Example 10: This example differs from Example 1 in that the organic fertilizer is chicken manure, and the peanut straw is first greened at 105° C. for 25 minutes.

[0061] Example 11: This example differs from Example 1 in that the organic fertilizer is cow dung, and the wheat straw is first sterilized at 105°C for 30 minutes.

[0062] Example 12: This example differs from Example 1 in that the irradiation dose per kg of sunflower straw is 0.4 kGy.

[0063] Example 13: This example differs from Example 1 in that the irradiation dose per kg of sunflower straw is 0.5 kGy.

[0064] Example 14: This example differs from Example 1 in that the product is dried at 65°C to a constant weight and finally crushed to pass through a 0.2 mm sieve.

[0065] Example 15: This example differs from Example 1 in that the product is dried at 75°C to a constant weight and finally crushed to pass through a 0.2 mm sieve.

[0066] Example 16: This example differs from Example 1 in that the method for preparing the organic fertilizer is as follows: pig manure, bran, and urea are mixed in a mass ratio of 10:3:1.5, and water is added to obtain a compost material having a water content of 53%, and then an EM fermentation agent accounting for 1.8 wt % of the compost material is added to the compost material, and the compost material is aerobically fermented at 40°C for 2 days to obtain a fecal fermentation product, which is dried and crushed to obtain an organic fertilizer.

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

[0068] Example 18: This example differs from Example 16 in that chicken manure, bran, urea and Sophora flavescens extract are mixed in a mass ratio of 10:3:1:1, and water is added to obtain a compost material with a water content of 55%.

[0069] Example 19: This example differs from Example 16 in that 1.5 wt% of EM fermentation agent is added to the compost material and aerobic fermentation is carried out at 35° C. for 1 day.

[0070] Example 20: This example differs from Example 16 in that 2 wt% of EM fermentation agent is added to the compost material and aerobic fermentation is carried out at 45° C. for 3 days.

[0071] Example 21: This example differs from Example 16 in that, during the fixing process, 0.5-1% by weight of a stalk of Cuscuta australis extract is added to the straw. The preparation method of the stalk of Cuscuta australis extract is as follows:

[0072] 1) First, place the Radix Polygoni Multiflori in an ice bath at a mass ratio of ice to Radix Polygoni Multiflori of 3:1. After standing for 8 minutes, the Radix Polygoni Multiflori powder was crushed to obtain Radix Polygoni Multiflori powder. The Radix Polygoni Multiflori powder and a 25% KOH aqueous solution were uniformly mixed at a solid-liquid ratio of 1 g:38 ml to obtain a mixed solution. The mixed solution was treated in a water bath at 70°C for 1 hour, and then solid-liquid separation was performed to obtain a supernatant.

[0073] 2) The supernatant obtained in step 1) was mixed with a solution having a concentration of 1.5 to 2.0 × 10 8 cfu / ml of Schizophyllum bacterial liquid were mixed at a volume ratio of 1:0.25 and subjected to ultrasonic extraction for 25 min at an ultrasonic power of 290 W, an ultrasonic frequency of 70 kHz, and an ultrasonic treatment temperature of 30°C to obtain an extract;

[0074] 3) The extract obtained in step 2) was concentrated under reduced pressure to 12 times the original concentration, 37% hydrochloric acid was added to the obtained concentrate to adjust the pH to 4.5, and 2.8 times the volume of ethanol was added to the filtrate obtained by filtering at a filter diameter of 10 μm for alcohol precipitation to obtain a precipitate, which was freeze-dried at -60°C to obtain a Polygonum multiflorum extract.

[0075] Example 22: This example is different from Example 21 in that the mass ratio of ice to tuberculosis is 1:1, and the mixture is allowed to stand for 5 minutes. The tuberculosis powder and 20% by mass of KOH electrolyzed water are evenly 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: This example is different from Example 21 in that the mass ratio of ice to tuberculosis is 5:1, and the mixture is allowed to stand for 10 minutes. The tuberculosis powder and 30% by mass KOH electrolyzed water are evenly 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 2 hours.

[0077] Example 24: This example differs from Example 21 in that the supernatant and concentration are 1.5×10 8 The culture solutions of Schizophyllum sp. and CFU / ml were mixed at a volume ratio of 1:0.2 and subjected to ultrasonic extraction for 20 min.

[0078] Example 25: This example differs from Example 21 in that the supernatant and concentration are 2.0×10 8 The culture solutions of Schizophyllum sp. and CFU / ml were mixed at a volume ratio of 1:0.3 and subjected to ultrasonic extraction for 30 min.

[0079] Example 26: This example differs from Example 21 in that the extract is concentrated under reduced pressure to 10 times the original concentration, the obtained concentrate is adjusted to pH 4 by adding hydrochloric acid, and ethanol 3 times the volume of the filtrate is added to the filtrate obtained by filtration for alcohol precipitation.

[0080] Example 27: This example differs from Example 21 in that the extract is concentrated under reduced pressure to 15 times the original concentration, the obtained concentrate is adjusted to pH 5 by adding hydrochloric acid, and ethanol 2.5 times the volume of the filtrate is added to the filtrate obtained by filtration for alcohol precipitation.

[0081] Example 28: This example differs from Example 21 in that the method for returning the straw powder to the field is:

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

[0083] Add straw powder to the three layers of soil in sequence, where 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 The unit is kg / hm 2 , i is the number of layers, taking 1, 2, 3, M = 10000; W i =(M×TP i )×[H i / (H1+H2+H3)], that is, W1=3078, W2=1578, W3=631.

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

[0085] Example 30: This example differs from Example 28 in that H1:H2:H3=5:3:2.

[0086] Example 31: This example differs from Example 28 in that M=9000.

[0087] Example 32: This example differs from Example 28 in that M=11000.

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

[0089] Experimental design: To illustrate the stimulating effect of combining organic fertilizer with straw in reducing N2O emissions, the present invention used Urumqi soil (UQ) and Gongzhuling soil (GZL) as the following experimental groups, with the soil treatment parameters of Example 1 as the benchmark and control;

[0090] Control 1: no fertilizer (CK);

[0091] Control Example 2: Application of NPK fertilizer (NPK);

[0092] Control Example 3: Application of straw and NPK fertilizer (NPKS);

[0093] Control Example 4: Application of organic fertilizer and NPK fertilizer (NPKM);

[0094] The straw powder applied in this application was labeled, and then the labeled straw powder was added to the control examples 1 to 4. The control example 4 with the added labeled straw powder is Example 1 of this application. The cumulative N2O emissions of four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition and the effect of straw addition on N2O emissions were analyzed. The results are as follows: Figures 1 to 4 As shown:

[0095] Figure 1 The results show that during the 180-day incubation period, the soil from Urumqi (UQ, Figure 1 a) Gongzhuling soil (GZL, Figure 1 b) N2O emission rates, and cumulative N2O emissions from four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition ( Figure 1 c) and the effect of straw addition on N2O emissions ( Figure 1 d); Straw addition immediately increased soil N2O emission rate, with a stronger response in the CK treatment than in the NPKM treatment, and then decreased exponentially during the incubation period ( Figure 1 a and 1b). The effect of straw addition on N2O emissions strongly depends on fertilization practices ( Figure 1 c). Under all fertilization and straw addition treatments, N2O emissions from GZL soil increased by an average of 83% compared to UQ soil ( Figure 1 c). In the absence of straw, fertilization significantly increased N2O emissions, increasing by 22-168% compared to the CK treatment, except for the NPKS treatment in the GZL soil. After straw addition, N2O emissions increased by 11-50% in the NPKM treatment and 94-141% in the CK treatment, compared to the corresponding no-straw treatment ( Figure 1 d);

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

[0097] Figure 3 The relative abundance of anaerobic ammonium-oxidizing bacteria (Anaerolineae, a) and (Eurotiomycetes, b) in four long-term fertilized soils (CK; NPK; NPKS; NPKM) with and without straw addition during a 180-day incubation period is shown; fertilization and straw addition significantly altered the soil microbial community composition ( Figures 6 to 8 ; Figure 3 ). PCoA analysis showed that there was a clear separation of bacterial and fungal compositions between the fertilization and straw addition treatments ( Figure 7 Notably, fertilization explained more of the differences in bacterial and fungal community composition (47-91%) than straw addition (3-16%). Figure 7At the order level, fertilization (NPK, NPKS, and NPKM treatments; 0.4-3.8%) significantly reduced the relative abundance of Anaerolineae in UQ and GZL soils compared with CK treatment (2.4-4.2%). Figure 3 a). Straw addition significantly increased the relative abundance of Eurotiomycetes in UQ soils under CK, NPKS, and NPKM treatments by 27%, 23%, and 53%, respectively, compared with the corresponding non-straw addition treatments ( Figure 3 b). RF analysis showed that Anaerolineae bacteria and Eurotiomycetes fungi are important microbial groups regulating N2O emissions ( Figure 3 c). Regression analysis further revealed that N2O emissions were significantly negatively correlated with the relative abundance of Anaerolineae (R 2 =0.53, p<0.001), and was significantly positively correlated with the relative abundance of Eurotiomycetes (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 was shown; microbial nitrogen-related functional genes were strongly affected by fertilization and straw addition. Compared with the CK treatment, the abundance of amoA and hao in the NPKM treatment was significantly reduced by 22-60% and 22-31%, respectively, while the abundance of amoB was not statistically different ( Figure 4 ac). Compared with CK treatment, the abundance of nirK and nosZ genes in NPKM treatment was significantly reduced by 6-7% and 1-10%, but the abundance of narG and norB genes was significantly increased by 19-25% and 28-59%, respectively ( Figure 4 dg). In all fertilization treatments, straw addition significantly reduced the abundance of amoA, amoB, hao, and nirK genes, while increasing the abundance of narG, norB, and nosZ genes compared with the treatment without straw addition.

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

[0100] It can be seen from the above results that N2O emissions from GZL soil were higher than those from UQ soil under all fertilization and straw addition treatments. Straw addition strongly stimulated N2O emissions from 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 stimulated N2O emissions, while long-term fertilization reduced the stimulating effect of N2O emissions. Fertilization alleviated the positive effect of straw return on N2O emissions by enhancing complete denitrification after straw addition. These results indicate that the response degree of straw addition to N2O emissions is affected by long-term fertilization measures. The present invention emphasizes the key role of fertilization, especially organic fertilizer application, in reducing the stimulating effect of straw return on N2O emissions in agricultural ecosystems.

[0101] Related performance experiments: Comparing the actual performance of the present invention under different experimental conditions, the N2O emissions of each embodiment were compared with Example 1 to explore the increase or decrease in N2O emissions of each embodiment compared with Example 1. Specific data are shown below.

[0102] 1. Explore the effects of the fertilization parameters and straw return parameters of this application on N2O emissions.

[0103] from Figure 9 It can be seen that, compared with Examples 1 to 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 the soil is too small or too large, and the field water holding capacity is too small or too large, which will increase the N2O emission rate. Therefore, in comprehensive comparison, the parameter effect of Example 1 is relatively better.

[0104] 2. Investigate the impact of straw preparation parameters on N2O emissions in this application.

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

[0106] from Figure 10 The results show that the microbial decomposition and utilization efficiency of Control Example 5 is lower than that of Examples 1 and 10 to 15 due to the lack of electron beam irradiation treatment on the straw. Therefore, it is shown that the decomposition and utilization efficiency of the straw by the electron beam irradiation can effectively reduce the N2O emission rate.

[0107] By comparing Example 1 and Examples 10 to 15, it can be seen that too small or too large fixing parameters, too small or too large irradiation parameters, and too small or too large drying and crushing parameters will increase the N2O emission rate. Therefore, in comprehensive comparison, the parameter effect of Example 1 is relatively better.

[0108] 3. Investigate the impact of the organic fertilizer preparation parameters of this application on N2O emissions.

[0109] from Figure 11 The results show that composting livestock manure with bran, EM bacteria and other agents has a better effect on reducing N2O emission rate than ordinary livestock manure.

[0110] By comparing Example 1 and Examples 16 to 20, it can be seen that if the proportion of livestock manure is too small or too large, and if the aerobic fermentation parameters of the fermentation agent are too small or too large, the N2O emission rate will increase. Therefore, in comprehensive comparison, the parameter effect of Example 16 is relatively better.

[0111] 4. Investigate the effect of adding Polygonum multiflorum extract to straw on N2O emissions.

[0112] The difference between Control Example 6 and Example 21 is that the extract of Polygonum multiflorum does not contain Schizophyllum;

[0113] from Figure 12 The results show that the addition of the Sophora flavescens extract to the straw provides regulating substances and trace elements to the soil, thereby reducing nitrogen loss and N2O emissions, and significantly reducing the N2O emission rate compared to Example 1. In Control Example 6, the Sophora flavescens extract lacks Schizophyllum sp., which reduces microbial metabolism and enzymatic hydrolysis compared to Examples 21 to 27, and thus significantly increases the N2O emission rate.

[0114] By comparing Examples 21 to 27, it can be seen that if the ice bath treatment parameters of Polygonum multiflorum are too small or too large, the proportion of Schizophyllum sphaerocephalum liquid is too small or too large, and the alcohol precipitation parameters are too small or too large, N2O emissions will be increased. Therefore, in comprehensive comparison, the parameter effect of Example 21 is relatively better.

[0115] 5. Investigate the effects of straw and organic fertilizer addition on N2O emissions at different soil depths.

[0116] The difference between Control Example 7 and Example 28 is that the amount of straw powder added to each layer of soil is the same;

[0117] from Figure 13 The results show that in Control Example 7, the same amount of straw powder was added to each layer of soil, but there was a lack of differential comparison of the nutrients required for each layer of soil, thus failing to meet the nitrogen conversion requirements of soils at different depths, resulting in a significant increase in the N2O emission rate compared to Examples 28 to 32.

[0118] Comparing Examples 21 and 28 to 32, it can be seen that adding straw powder according to a specific ratio at each soil depth can promote the growth and metabolism of beneficial microorganisms such as denitrifying bacteria, thereby reducing N2O emissions and further reducing the N2O emission rate compared to Example 21;

[0119] Comparing Examples 28 to 32, it can be seen that if the difference in soil depth between each layer is too small or too large, or if the amount of straw powder added to each layer is too small or too large, the N2O emission rate will increase. Therefore, in comprehensive comparison, the parameter effect of Example 28 is relatively better.

Claims

1. A method for reducing N2O emissions stimulated by returning straw to fields, characterized in that: When returning straw to the fields, apply NPK fertilizer and organic fertilizer to the soil.

2. The method for reducing N2O emissions stimulated by returning straw to fields according to claim 1, characterized in that: The application amount of the NPK fertilizer includes N 250~400kg / hm 2 、P2O5 80~150kg / hm 2 、K2O 80~150kg / hm 2 , the application rate of organic fertilizer is 25000~35000kg / hm 2 The amount of straw returned to the field is 4500~7500kg / hm 2 .

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

4. The method for reducing N2O emissions stimulated by returning straw to fields according to claim 1, characterized in that: It also includes further adjusting the soil C / N ratio to 25-30 based on the properties of the soil itself.

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

6. The method for reducing N2O emissions stimulated by returning straw to fields according to 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 returning straw to fields according to claim 6, characterized in that: The straw is straw powder, and the preparation method of the straw powder is as follows: The straw was first fixed at 105°C for 25-30 minutes, and then irradiated with electron beams at a dose of 0.4-0.5 kGy per kg of straw. The straw was then dried at 65-75°C to a constant weight, and finally pulverized and passed through a 0.2 mm sieve to obtain straw powder.

8. The method for reducing N2O emissions stimulated by returning straw to fields according to claim 7, characterized in that: During the fixing process, 0.5-1% of the mass of the tuberculiae ternatea extract is added to the straw. The preparation method of the tuberculiae ternatea extract is as follows: 1) first placing the tuberculinum sibiricum in an ice bath with a mass ratio of ice to tuberculinum sibiricum of 1-5:1, letting it stand for 5-10 minutes, then crushing it to obtain tuberculinum sibiricum powder, and uniformly mixing the tuberculinum sibiricum powder with a 20-30% by mass KOH aqueous solution at a solid-liquid ratio of 1 g:35-40 ml to obtain a mixed solution, treating the mixed solution in a water bath at 65-75°C for 0.5-2 hours, and performing solid-liquid separation to obtain a supernatant; 2) The supernatant obtained in step 1) was mixed with a solution having a concentration of 1.5 to 2.0 × 10 8 cfu / ml of Schizophyllum bacterial liquid were mixed at a volume ratio of 1:0.2-0.3 and subjected to ultrasonic extraction for 20-30 minutes to obtain an extract; 3) The extract obtained in step 2) is concentrated under reduced pressure to 10 to 15 times the original concentration, the concentrated solution is adjusted to pH 4 to 5 by adding hydrochloric acid, and the filtrate obtained by filtration is added with ethanol in an amount of 2.5 to 3 times the volume of the filtrate for alcohol precipitation to obtain a precipitate, which is freeze-dried to obtain a Polygonum multiflorum extract.

9. The method for reducing N2O emissions stimulated by returning straw to fields according to claim 1, characterized in that: The preparation method of the organic fertilizer is: The method comprises mixing livestock and poultry manure, bran and urea in a mass ratio of 10:3:1-2, adding water to obtain a compost material with a water content of 50-55%, adding an EM fermentation agent accounting for 1.5-2 wt% of the compost material to the compost material, and aerobically fermenting the compost material at 35-45° C. for 1-3 days to obtain a manure fermentation product, which is dried and crushed to obtain an organic fertilizer.

10. The method for reducing N2O emissions stimulated by returning straw to fields according to claim 7, characterized in that: The method for returning the straw powder to the field is: First, the soil is divided into three layers from top to bottom. The thickness of the three layers are H1, H2, and H3, respectively. H1:H2:H3=4-5:3:2, and the soil porosity of each layer is TP i ; Add straw powder to the three layers of soil in sequence, where 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 The unit is kg / hm 2 , i is the number of layers, 1, 2, 3, M = 9000 ~ 11000; W i =(M×TP i )×[H i / (H1+H2+H3)].

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