Straw field carbon and yield increasing and greenhouse gas emission mitigation method and application

Abstract

The application provides a method for increasing carbon and yield and reducing greenhouse gas emission of farmland by returning straw to field and application thereof, and belongs to the technical field of returning straw to field. The method comprises the following steps: treating corn straw by using biogas slurry obtained by anaerobic fermentation of cow dung and corn straw, mixing the treated corn straw with EM microbial agent to carry out composting fermentation, and returning the fermented corn straw to field. The treatment and returning method of the corn straw can effectively seal the carbon source in the soil in the form of organic carbon, improve soil fertilizer, avoid emission of the carbon source in the form of greenhouse gas to the environment, and cause pollution to the environment, thereby achieving the technical effect of carbon sealing and fertilizer increasing, providing technical support for returning straw to field, and being helpful to the development of green agriculture.

Description

Technical Field

[0001] This invention relates to the field of straw return technology, and more specifically to a method and application of straw return to the field to increase carbon emissions and yield in farmland and mitigate greenhouse gas emissions. Background Technology

[0002] Black soil in Northeast China is highly fertile, easy to cultivate, and rich in organic matter, making it ideal for crop growth and resulting in high yields and quality. It plays an irreplaceable role in my country's agricultural production. However, with increasing demands from economic development, the black soil of Northeast China has long been overused, leading to a significant decline in soil organic matter content and a serious challenge to its protection. Crop straw, as a rich biological resource, can improve soil physicochemical properties, enhance soil fertility, and increase soil moisture when used properly. With increasing mechanization, returning straw to the field has become an important measure to improve soil conditions. However, improper straw return can lead to significant greenhouse gas emissions.

[0003] Climate change has become a major constraint on ensuring food security and ecosystem stability. Human activities have generated large amounts of greenhouse gases, severely impacting global warming. Therefore, reducing greenhouse gas emissions and enhancing carbon sequestration in farmland are effective ways to mitigate climate change. Severe depletion of soil organic carbon pools reduces soil quality, lowers biomass productivity, and adversely affects water quality. Global warming may exacerbate this depletion, making improving soil carbon sequestration in farmland considered the best measure for increasing fertility and reducing emissions.

[0004] Therefore, providing a reasonable straw return to the field measure to improve the return effect and control greenhouse gas emissions from farmland is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method and application for returning straw to the field to increase carbon emissions and yield in farmland and reduce greenhouse gas emissions. The invention not only properly treats agricultural waste, but also has the technical effects of soil fertilization and emission reduction, providing technical support for green agricultural production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for returning straw to the field to increase carbon emissions, improve yield, and mitigate greenhouse gas emissions in farmland includes the following steps:

[0008] (1) Collect corn stalks, air dry and crush them for later use;

[0009] (2) Collect cow dung, remove impurities, and set aside for later use;

[0010] (3) Mix cow dung, crushed corn stalks and biogas slurry to prepare anaerobic fermentation material, carry out anaerobic fermentation, and extract biogas slurry after gas production.

[0011] (4) The extracted biogas slurry was used to pretreat the corn straw, and EM bacteria were added to prepare compost material. The material was then subjected to aerobic fermentation to prepare corn straw composted organic fertilizer.

[0012] (5) The prepared corn straw composted organic fertilizer, combined with phosphate and potassium fertilizers, is used as base fertilizer for field application; the total nitrogen application rate during the entire growth period is 175-185 kg / hm. 2 The amount of nitrogen applied as base fertilizer accounts for 60-70% of the total nitrogen application during the entire growth period. The nitrogen application rate of well-rotted corn stalk organic fertilizer in the base fertilizer is 65-70 kg / hm². 2 Phosphate fertilizer carries 45-50 g / hm of nitrogen. 2 Urea is used to supplement the nitrogen content of the base fertilizer.

[0013] Preferably, the moisture content of the corn stalks after air drying in step (1) is 8-11%; and the particle size of the crushed stalks is 1mm-3.5cm.

[0014] Preferably, the moisture content of the cow dung in step (2) is 60-63%.

[0015] Preferably, the carbon-to-nitrogen ratio of the anaerobic fermentation material in step (3) is 28-30:1; the total solids content in the anaerobic fermentation material is 8%; the amount of biogas slurry added to the anaerobic fermentation material accounts for 8%-12% of the total volume of the fermentation material; and the temperature of the anaerobic fermentation is 35℃.

[0016] More preferably, the amount of biogas slurry added to the anaerobic fermentation material accounts for 10% of the total volume of the fermentation material.

[0017] Preferably, the pretreatment process of corn straw by biogas slurry in step (4) is as follows: mix biogas slurry with corn straw, the volume of biogas slurry is 30% of the volume of corn straw, and after thorough mixing, place in a sealed state for 7 days.

[0018] Preferably, the amount of EM agent added in step (4) is 6 mL / kg corn straw; the amount of biogas slurry added is 30% of the total weight of corn straw; the moisture content of the compost material is 60-65%, the carbon-nitrogen ratio is 25-30:1; the compost fermentation time is 22-26 days, the initial temperature of aerobic fermentation is 25℃, and the initial pH value is 6.5-7.0.

[0019] Preferably, during the aerobic fermentation process described in step (4), the pile is ventilated to maintain the center temperature of the pile at 42-53℃; the ventilation rate is 0.4L / min and the ventilation duration is 15min / h.

[0020] Preferably, the phosphate fertilizer in step (5) is diammonium phosphate, and the potassium fertilizer is potassium chloride; the application rate of the organic fertilizer is 6-8 kg / hm. 2 The application rate of phosphate fertilizer is 85-95 kg / hm². 2 The application rate of potassium fertilizer is 95-105 kg / hm². 2 .

[0021] Another object of the present invention is to provide the application of the above-mentioned straw return method for increasing carbon emissions and yields in farmland and mitigating greenhouse gas emissions in reducing greenhouse gas emissions and / or increasing carbon emissions and yields in farmland.

[0022] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention provides a method for increasing carbon emissions and yields in farmland while mitigating greenhouse gas emissions through straw return to the field. The method involves treating corn stalks with biogas slurry obtained from the anaerobic fermentation of cow dung and corn stalks, mixing it with EM (Effective Microorganisms) inoculant, and then returning the fermented straw to the field. This straw treatment and return method effectively sequesters the carbon source in the straw into the soil as organic carbon, improving soil fertility. Simultaneously, it avoids the emission of carbon sources into the environment as greenhouse gases, thus preventing environmental pollution. This achieves the technical effect of carbon sequestration and fertilization, providing technical support for straw return to the field and contributing to the development of green agriculture. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 For: Changes in soil organic carbon content after straw composting and returning to the field;

[0026] Figure 2 For: Changes in total soil nitrogen content after straw composting and returning to the field;

[0027] Figure 3 For: Changes in TOC and TN content in corn planted after straw composting and returning to the field;

[0028] Figure 4 For: Changes in soil CO2 emissions after straw composting and returning to the field;

[0029] Figure 5 For: Changes in soil CH4 emissions after straw composting and returning to the field;

[0030] Figure 6For: Changes in soil N2O emissions after straw composting and returning to the field. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for returning straw to the field to increase carbon emissions, improve yield, and mitigate greenhouse gas emissions includes the following steps:

[0034] (1) Air dry the corn stalks until the moisture content is 8-11% and the carbon-nitrogen ratio is 67-69:1, then crush them to 1mm-3.5cm and set aside;

[0035] (2) Collect cow dung, remove impurities from cow dung, the moisture content of cow dung is 60-63%, and the carbon-nitrogen ratio is 40-43:1;

[0036] (3) Mix cow dung and corn stalks evenly and put them into a fermentation container. Control the C / N ratio of cow dung and corn stalks to 28 and the total solid content to 8% during anaerobic co-fermentation. Add 10% of the total volume of biogas slurry to introduce methanogenic bacteria. Carry out anaerobic fermentation in a 35℃ water bath. After gas production, extract the biogas slurry.

[0037] (4) Organic fertilizer was prepared by treating corn straw with 30% biogas slurry and then mixing it with EM agent for fermentation. The amount of EM agent added was 6 mL / kg of corn straw. Water was added to adjust the moisture content to 60%-65%. The carbon-nitrogen ratio of the mixture was 25-30:1. Aerobic fermentation was carried out for 22-26 days. The initial fermentation temperature was 25℃. The fermentation pH was 6.5-7.0. The center temperature of the compost was 42-53℃ during the fermentation process. An air pump was used to ventilate the compost during the fermentation process. The ventilation rate of the air pump was 0.4 L / min, and ventilation was carried out for 15 minutes per hour. Organic fertilizer prepared by rapid decomposition of corn straw was obtained.

[0038] (5) The prepared organic fertilizer is returned to the field with all the straw, and the total nitrogen application rate during the entire growing season is 180 kg / hm. 2 The amount of nitrogen applied as base fertilizer accounts for 60-70% of the total nitrogen application during the entire growth period. The nitrogen application rate of well-rotted corn stalk organic fertilizer in the base fertilizer is 65-70 kg / hm². 2 Phosphate fertilizer carries 45-50 g / hm of nitrogen. 2 Urea was used to supplement the base fertilizer nitrogen, and diammonium phosphate and potassium chloride were applied at a rate of 90 kg / hm². 2 100kg / hm2 The main crop grown there is corn.

[0039] The experimental groups are shown in Table 1.

[0040] Table 1 Field Experiment Design for Straw Composting and Returning to the Field

[0041]

[0042] Note: Conventional fertilization refers to the replacement of urea with urea in the nitrogen provided by straw compost in the base fertilizer.

[0043] Soil samples were collected before and after straw composting and returning to the field in 2022 using a five-point sampling method. The sampling depth was 0–20 cm (topsoil). Samples were air-dried naturally, and visible organic residues such as straw were removed. The samples were then used to determine the soil organic carbon and total nitrogen content. Figures 1-2 The changes in TOC and TN content of maize during the early growth stage and after autumn harvest were measured. Figure 3 The effects of different soil treatments on ear weight, ear number, 100-grain weight, and yield of maize (Table 2); greenhouse gas emissions under different soil treatments (Table 2). Figures 4-6 ), and the global warming potential (GWP) during the maize growing season (Table 3).

[0044] Results analysis: such as Figure 1 As shown, in the early stage of crop growth, the SOC content in experimental group Z2 decreased. After the entire crop growth cycle, the SOC content in all groups increased, with the final increase in SOC content being Z1 (4.43 mg / kg) > Z2 (0.89 mg / kg) > CK (0.59 mg / kg). After the autumn harvest, i.e., after the entire planting process was completed, the organic matter content increased. The increase in organic matter content after straw composting and returning to the field was the most significant, at 7.64 g / kg. The SOC storage of the three experimental groups increased by Z1 (17.36%) > Z2 (3.79%) > CK (2.45%), respectively.

[0045] Figure 2 The changes in soil TN under different field treatments were shown. In the early stage of crop growth, the soil TN content in all three experimental groups decreased. After the crop planting was completed, the soil TN content in experimental groups Z1 and Z2 increased (compared to the dotted line), with Z1 (0.42 mg / kg) > Z2 (0.30 mg / kg). Returning straw to the field after composting was beneficial to increasing soil TN storage.

[0046] Figure 3The results showed that, compared with the control group, both treatments increased the carbon and nitrogen content of the corn. The straw composting and returning to the field increased the corn TOC content by 2.80 mg / kg, while conventional fertilization was beneficial to increasing the corn TN content by 6.14 mg / kg.

[0047] As shown in Table 2, the yield of maize under different soil treatments was calculated. The ear weight of different treatments was Z1>Z2>CK, the number of ears was CK>Z1>Z2, and the weight of 100 kernels was Z1>Z2>CK. The effects of straw composting and returning to the field and returning to the field with constant fertilizer on the weight of 100 kernels of maize were comparable. At the same time, the maize yield of the straw composting and returning to the field treatment was higher, exceeding that of the CK group by 1.06%.

[0048] Table 2. Maize yield under different treatments

[0049]

[0050] Note: Different letters indicate that the difference is significant at the 5% level.

[0051] Several quadrats are randomly selected in the cornfield, with each quadrat typically having an area of ​​1-10 m². 2 Greenhouse gases were collected and measured using a static chamber-gas chromatography method. Sampling was conducted between 10:00 AM and 12:00 PM, with each chamber session lasting 30 minutes. Experimental data were statistically analyzed using SPSS 21.0 and plotted using Origin 2018. The results are as follows:

[0052] like Figure 4 As shown, the soil CO2 emission patterns were basically consistent across different field treatments. Soil CO2 emission flux was low in May, a period immediately following fertilization and during the early growth stage of maize. During this stage, the differences in soil CO2 emissions among different treatments were relatively small. Comparatively, soil CO2 emission flux was higher when straw compost was returned to the field, with an average emission flux of 7.62 mg / m³. 2 / h, the soil CO2 emission flux under conventional fertilization is 6.52 mg / m³. 2 / h, this is because straw composting and nitrogen fertilizer application provide direct carbon and nitrogen sources to the soil, thus increasing the soil respiration rate. Soil CO2 emissions reach a relatively high peak in June and July, coinciding with the early stages of maize growth and periods of high rainfall. Both straw composting and conventional fertilization significantly increase soil CO2 emission flux, but the increase is smaller under the maize straw composting and returning treatment. Throughout the crop growing season, the soil CO2 emission flux is CK(69.16 mg / m³). 2 / h)>Z2(63.02mg / m 2 / h)>Z1(60.55mg / m2 / h).

[0053] like Figure 5 As shown, during field fertilization and the early stages of maize growth, the CH4 gas emission flux in the soil increased with both conventional fertilization and straw composting treatments. During this period, the CH4 gas emission flux Z2 in the three experimental groups was -0.11 mg / m³. 2 / h)>CK(-0.12mg / m 2 / h)>Z1(0.20mg / m 2 Although the total CH4 gas emission flux was less than zero during June and July, the average emission flux during this period was Z2 (0.15 mg / m³). 2 / h), Z1 (0.11mg / m 2 The CH4 gas emission flux was greater than zero during the entire crop growing season. This was because the organic fertilizer introduced a large amount of easily soluble organic matter, and the increased content of easily decomposable organic matter in the soil provided more reaction substrates for methanogenic bacteria, thus promoting CH4 emissions. Ultimately, the soil CH4 emission flux during the entire crop growing season was Z2(-0.11 mg / m³). 2 / h)>Z1(-0.63mg / m 2 / h)>CK(-9.79×10 -4 mg / m 2 / h).

[0054] like Figure 6 As shown, soil N2O emissions showed a slight decreasing trend in the blank control group and the conventional fertilization group during field fertilization and the early stages of maize growth, but this trend was not significant. The soil N2O emission flux in the straw composting and returning-to-the-field treatment also showed a decreasing trend. From June to September and from the maize jointing stage to maturity, the soil N2O emission flux in the conventional fertilization treatment showed a trend of first decreasing and then increasing, while the soil N2O emission flux in the straw composting and returning-to-the-field treatment showed a trend of first increasing and then decreasing. The application of organic fertilizer introduces a large amount of soluble organic matter into the soil, increasing the substrate for denitrifying bacteria. Some studies also suggest that farmland N2O emissions are mainly affected by the content of nitrate nitrogen and ammonia nitrogen in the soil; the content of nitrate nitrogen and ammonia nitrogen in the soil decreased under straw composting and returning-to-the-field treatment. Ultimately, the soil N2O emission flux during the entire crop growing period was Z2 (0.63 mg / m³). 2 / h)>Z1(0.43mg / m 2 / h)>CK(0.37mg / m 2 / h).

[0055] The global warming potential (GWP) during the maize growing season was calculated. The total GWP during the maize growing season was mainly contributed by CO2, followed by CH4, while N2O contributed very little. Conventional fertilization increased the total GWP during the maize growing season by 10.96% compared to the control group, while straw composting and returning to the field decreased the total GWP during the maize growing season by 0.99% compared to the control group. Greenhouse gas emission intensity was calculated, and the results are shown in the table. Conventional fertilization resulted in the highest soil greenhouse gas emission intensity, exceeding the control group by 10.96%. Straw composting and returning to the field decreased the soil greenhouse gas emission intensity, decreasing by 0.99% compared to the control group.

[0056] Table 3. Soil greenhouse gas warming effect under different treatments

[0057]

[0058] The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for returning straw to the field to increase carbon emissions and yield while mitigating greenhouse gas emissions, characterized in that, Includes the following steps: (1) Collect corn stalks, air dry and crush them for later use; (2) Collect cow dung, remove impurities, and set aside for later use; (3) Mix cow dung, crushed corn stalks and biogas slurry to prepare anaerobic fermentation material, carry out anaerobic fermentation, and extract biogas slurry after gas production. (4) The extracted biogas slurry was used to pretreat the corn straw, and EM bacteria were added to prepare compost material. The material was then subjected to aerobic fermentation to prepare corn straw composted organic fertilizer. (5) The prepared corn straw decomposed organic fertilizer is combined with phosphate fertilizer and potassium fertilizer and used as base fertilizer for field fertilization; the total nitrogen application during the whole growth period is 175-185 kg / hm, the nitrogen application of base fertilizer accounts for 60-70% of the whole growth period, the nitrogen application of corn straw decomposed organic fertilizer in base fertilizer is 65-70 kg / hm, the nitrogen content of phosphate fertilizer is 45-50 g / hm, and urea is used to supplement the nitrogen content of base fertilizer. The moisture content of the air-dried corn stalks described in step (1) is 8-11%; the particle size of the crushed stalks is 1mm-3.5cm. The moisture content of the cow dung in step (2) is 60-63%; The carbon-to-nitrogen ratio of the anaerobic fermentation material in step (3) is 28-30:1; the total solids content in the anaerobic fermentation material is 8%; the amount of biogas slurry added to the anaerobic fermentation material accounts for 8%-12% of the total volume of the fermentation material; and the temperature of the anaerobic fermentation is 35℃. The pretreatment process of corn straw by biogas slurry in step (4) is as follows: mix biogas slurry with corn straw, the volume of biogas slurry is 30% of the volume of corn straw, mix thoroughly and evenly, and then place in a sealed state for 7 days; The amount of EM agent added in step (4) is 6 mL / kg corn straw; the moisture content of the compost material is 60-65%, the carbon-nitrogen ratio is 25-30:1; the aerobic fermentation time is 22-26 days, the initial temperature of compost fermentation is 25℃, and the initial pH value is 6.5-7.

0. During the aerobic fermentation process described in step (4), the pile is ventilated to maintain the center temperature of the pile at 42-53℃; the ventilation rate is 0.4L / min and the ventilation duration is 15min / h. The straw return method described above, which increases carbon emissions and reduces greenhouse gas emissions in farmland, is applicable to corn.

2. The method for returning straw to the field to increase carbon emissions and reduce greenhouse gas emissions in farmland according to claim 1, characterized in that, The phosphate fertilizer mentioned in step (5) is diammonium phosphate, and the potassium fertilizer is potassium chloride; the application rate of the organic fertilizer is 6-8 kg / hm. 2 The application rate of phosphate fertilizer is 85-95 kg / hm². 2 The application rate of potassium fertilizer is 95-105 kg / hm². 2 .

3. The application of the straw return method for increasing carbon emissions and reducing greenhouse gas emissions in farmland as described in any one of claims 1-2 in reducing greenhouse gas emissions and / or increasing carbon emissions and production in farmland.

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