Green manure and feed manure dual-purpose fertilizer-saving and emission-reducing planting and returning method

Abstract

The invention relates to the technical field of agriculture, in particular to a green manure and feed manure dual-purpose fertilizer-saving emission-reducing planting and returning method which comprises the following steps: sowing wheat in mid-March, and harvesting wheat in late July; the green manure is sown after wheat harvesting, and common vetch and highland barley are sown in a mixed mode; after frost falls in the last ten days of October, grazing is conducted on the green manure land parcel, the upper portion of the green manure land is naturally eaten and then converted into sheep manure, and returning to the field through the abdomen is achieved; at the beginning of November, deeply ploughing the green manure plot, and turning and burying sheep manure and green manure stubbles into soil. According to the method, direct returning of traditional green manure overground tissue to the field is converted into returning of sheep manure and green manure stubbles to the field, and nitrogen fertilizer saving and farmland greenhouse gas emission reduction can be achieved synchronously by means of the characteristics that the sheep manure is high in C / N and low in decomposition rate after returning to the field on the premise that nutrients are not lost.

Description

Technical Field

[0001] The invention relates to the technical field of agriculture, in particular to a method for returning green manure and feed fertilizer to fields for saving fertilizer and reducing emissions. Background Art

[0002] Agricultural production is a significant source of global greenhouse gas emissions. Driven by high yields, nitrogen fertilizers are widely overused, exacerbating greenhouse gas emissions from farmland. Planting green manure and returning it to the fields can replace some chemical fertilizers, reducing the input of chemical nitrogen fertilizers while improving soil physical and chemical properties. By influencing the microenvironment and microbial activity, this alters key steps in the soil carbon and nitrogen cycle, thereby affecting soil greenhouse gas production and emissions. This approach is expected to reduce greenhouse gas emissions while also reducing the use of nitrogen fertilizers.

[0003] However, green manure has a low carbon-nitrogen ratio and decomposes rapidly after being returned to the field, providing ample substrate for nitrifying and denitrifying bacteria, which in turn promotes soil N₂O emissions. Furthermore, returning green manure to the field increases soil organic carbon content, enhances soil aeration, and accelerates the decomposition of soil organic carbon, leading to increased soil CO₂ emissions. Therefore, it is urgent to explore a suitable method for returning green manure to the field to achieve fertilizer conservation and emission reduction. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to propose a method for returning green manure to the field for both fertilizer saving and emission reduction.

[0005] In order to achieve the above object, the technical solutions specifically adopted by the present invention are as follows:

[0006] A method for returning green manure to the field for both fertilizer saving and emission reduction, wherein the planting pattern of the method adopts wheat-based green manure cropping, that is, spring wheat is sown first, and green manure is sown after the wheat is harvested; the green manure is returned to the field by returning the aboveground part of the green manure to the field in combination with the root stubble, specifically comprising the following steps:

[0007] S1, sow wheat in mid-March and harvest in late July;

[0008] S2. Green manure is sown after wheat harvest, using a mixture of pea and barley;

[0009] S3. After frost in late October, graze on the green manure plots, and the aboveground part of the green manure will be naturally eaten and converted into sheep manure, which will be returned to the fields;

[0010] S4. In early November, deep plow the green manure plot and bury the sheep manure and green manure roots and stubble into the soil.

[0011] Furthermore, in step S1, the wheat sowing density is 6.75 million grains / hm2. 2 , adopt row sowing method, with row spacing of 12cm.

[0012] Furthermore, in step S2, green manure is sown in early August at the latest, and the sowing rate of mixed sowing of arrow pea and highland barley is 180kg / hm2 respectively. 2 and 52.5kg / hm 2 .

[0013] The present invention has the following characteristics and beneficial effects:

[0014] The aboveground tissue of traditional green manure is directly converted into sheep manure and green manure stubble and returned to the fields. Under the premise of ensuring that nutrients are not lost, the high C / N ratio of sheep manure and the slow decomposition rate after returning to the fields can be used to simultaneously achieve nitrogen fertilizer savings and reduce greenhouse gas emissions from farmland. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0016] Figure 1 The impact of nitrogen fertilizer reduction and different green manure incorporation methods on global warming potential;

[0017] Figure 2 To study the effects of nitrogen fertilizer reduction and different green manure return methods on wheat grain yield;

[0018] Figure 3 The effects of nitrogen fertilizer reduction and different green manure return methods on greenhouse gas emission intensity;

[0019] Figure 4 Effects of nitrogen fertilizer reduction and different green manure return methods on soil physical and chemical indicators

[0020] In the figure: (a) soil bulk density, (b) pH, (c) soil organic matter, (d) ammonium nitrogen, and (e) nitrate nitrogen.

[0021] Figure 5 To study the effects of nitrogen fertilizer reduction and different green manure return methods on soil biological indicators;

[0022] In the figure: (a) soil urease, (b) soil sucrase, (c) soil nitrite reductase, and (d) soil nitrate reductase.

[0023] Figure 6 Correlation analysis between soil characteristics and global warming potential, grain yield and greenhouse gas emission intensity;

[0024] In the figure: (a) is the Mantel test of global warming potential, grain yield and greenhouse gas emission intensity and soil physical and chemical indicators. The width and fineness of the lines indicate the strength of the relationship between global warming potential, grain yield and greenhouse gas emission intensity and soil physical and chemical indicators; the solid line represents positive correlation, and the dotted line represents negative correlation; the color of the square represents the correlation between soil factors; (b) is the random forest model analysis of greenhouse gas emission intensity. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0026] Example 1

[0027] S1: Wheat was sown in mid-March with a sowing density of 6.75 million grains / hm2. 2 , sown in rows with a row spacing of 12 cm, and harvested in late July;

[0028] S2. Green manure should be sown in early August at the latest after wheat harvest. Mix pea and highland barley at a sowing rate of 180 kg / hm2. 2 and 52.5kg / hm 2 ;

[0029] S3. After frost in late October, the green manure plots are grazed, and the aboveground part of the green manure is naturally eaten and converted into sheep manure, which is then returned to the fields;

[0030] S4. Deep plow the grazing land in early November to ensure that the sheep manure and green manure roots are buried in the soil.

[0031] Test data:

[0032] 1.1 Experimental design

[0033] This experiment was conducted at the Academy of Sciences experimental site from 2023 to 2024. The soil type was chestnut soil. The physical and chemical properties of the soil at 0-20 cm were as follows: pH 8.2, organic matter 15.8 g / kg, total nitrogen 1.27 g / kg, available phosphorus 10.2 mg / kg, and available potassium 157 mg / kg. The experiment used a split-plot design. The main plot was divided into three nitrogen application levels during the wheat season: conventional nitrogen (N2, 225 kg / hm2) and nitrogen (N2, 225 kg / hm2). 2 ), nitrogen reduction by 30% (N1, 158kg / hm 2) and no nitrogen (NO). Three methods of returning manure to the field during the green manure season were set up in the sub-plot: returning only the stubble (RR), returning the aboveground part and stubble (SDRR), and returning all the aboveground and stubble (RROS). Nine treatments were applied, each with three replicates, in plots of 15 m² (5 × 3 m).

[0034] The spring wheat variety used in the trial was Qingchun 38, and the green manure used in the trial was a mixture of pea and barley. The pea variety was Ximu 333, and the sowing rate was 180kg / hm2. 2 The highland barley variety is Kunlun No. 15, and the sowing rate is 52.5 kg / hm 2 Fertilizer application consisted of urea (46%) applied at a base fertilizer / topdressing ratio of 8:2, with superphosphate (15%) applied as a base fertilizer at a rate of 95 kg / hm². Green manure was sown in early August and mowed in late October. RR crops were treated with the following methods: the aboveground portion of the crops was removed, leaving only the root stubble (15 cm thick), the aboveground portion of the SDRR crops was used as feed, and sheep manure was returned to the fields. The entire amount of RROS crops was returned to the fields. Wheat was drill-sown in mid-March (6.75 million grains / hm², 12 cm row spacing) and harvested in late July. Standard irrigation and field management were applied throughout the experiment.

[0035] Table 1 Basic nutrient content of green manure hay

[0036]

[0037] 1.2 Measurement indicators and calculation methods

[0038] 1.2.1 Converting the amount of sheep manure applied after returning green manure to the field

[0039] The formula for converting the amount of sheep manure applied when returning green manure to the field is as follows:

[0040]

[0041] In the formula, the weight of the aboveground part of the green manure was uniformly cut and weighed after frost in October. The nitrogen content of the aboveground part of the green manure was determined using a fully automatic carbon form nitrogen analyzer produced by SkalaR. The values are shown in Table 1. The recovery rate is the ratio of the nitrogen content in sheep feces and urine after the sheep eat the green manure to the total nitrogen content of the green manure, which is 60.1%.

[15] The nitrogen content of decomposed sheep manure is shown in Table 2.

[0042] Table 2 Basic nutrient content of the tested decomposed sheep manure

[0043]

[0044] 1.2.2 Total greenhouse gas emissions

[0045] CO2, CH4, and N2O emissions: CO2, CH4, and N2O were collected using a static chamber method, and their concentrations were determined using a gas chromatograph (Angilent, HP4890D). The static chamber was constructed of stainless steel sheet metal, measuring 50 cm × 50 cm × 60 cm. It contained an air mixing blower, an air pressure equalization tube, a thermometer, and sample collection tubes. The chamber was covered with a white cotton sheath for thermal insulation. The upper end of the base contained a water reservoir that could be inserted into the chamber. During measurements, water was added to the reservoir to seal the chamber. The lower end of the base protruded into the soil to secure it. The sheet metal protrusion had evenly distributed circular holes to minimize interference with crop growth. Measurements were taken every 15 days. Each measurement began between 9:00 AM and 12:00 PM, with gas samples drawn from the chamber every 10 minutes for a total of three times. After collection, samples were brought back to the laboratory and analyzed within 48–72 hours.

[0046] The total amount of CO2, CH4 and N2O emissions is calculated as follows:

[0047]

[0048] Where F i 、F i-1 are the greenhouse gas emission fluxes measured for the i-th and i-1-th times respectively; d is the number of days between the i-th and i-1-th observations; 24 is the number of hours per day, 10 -2 is the unit conversion; n is the total number of gas measurements; f is the total amount of gas emissions during the growth period.

[0049] Static chamber temperature: Secure the thermometer to the rubber stopper in the top opening of the static chamber. Take the first reading 10 minutes after the static chamber is installed and ready. Then, record the reading every 10 minutes for a total of three times. The chamber temperature corresponds to the sampled gas, so a gas sample should be collected immediately after each reading.

[0050] 1.2.3 Global Warming Potential

[0051] The formula for calculating the global warming potential (GWP) is as follows:

[0052]

[0053] Where GWP is the global warming potential (kg CO2eq), fCO2, fN2O and fCH4 are soil CO2 (kg C hm -2 )、N2O(kg N hm -2 ) and CH4 (kg C hm -2) total emissions; 44 / 12, 44 / 28, and 16 / 12 are the coefficients for converting the net emissions of CO2, N2O, and CH4 into CO2 emissions, respectively; 298 is the warming potential multiple of N2O relative to CO2 on a century-long scale; 25 is the warming potential multiple of CH4 relative to CO2 on a century-long scale.

[0054] 1.2.4 Grain yield

[0055] Each plot, except for the protected row, was harvested separately, air-dried and threshed, and then weighed to calculate the yield. The moisture content of the grain was measured using a PM-8188 grain moisture meter, and the average of three measurements was used to calculate the grain yield based on the 13% moisture content standard.

[0056] 1.2.5 Greenhouse gas emission intensity

[0057] The calculation formula for greenhouse gas emission intensity (GHGI) is as follows:

[0058] GHGI=GWP / Y (4)

[0059] Where GHGI is the greenhouse gas emission intensity; GWP is the global warming potential; and Y is the rice yield.

[0060] 1.2.6 Soil bulk density

[0061] The soil bulk density was determined using the ring knife method at the sampling point. The specific calculation method is as follows:

[0062]

[0063] Where Rs is the soil bulk density (g·cm -3 ), m1 is the weight of the ring knife (g), m2 is the weight of the ring knife and the dried sample (g), v is the volume of the ring knife (cm -3 ).

[0064] 1.2.7 Soil biochemical characteristics

[0065] A five-point sampling method was used to collect soil samples from 0-20 cm after the wheat harvest in 2023 and 2024. After removing the residue, the soil samples were placed in self-sealing bags and taken back to the laboratory for soil index determination. Some samples were passed through a 1 mm sieve and the soil enzyme activity was determined using a kit provided by Coming Company. The remaining samples were air-dried at room temperature in the dark, ground and passed through a 0.25 mm sieve for soil chemical index analysis. Soil organic matter was determined using the potassium dichromate volumetric method, and pH was determined using the potentiometric method. The water-soil ratio was 1:2.5; ammonium nitrogen and nitrate nitrogen were determined using the Smart Chem 450 fully automatic discontinuous chemical analyzer produced by AMS Alliance, France, and total nitrogen was determined using the SNC-100 fully automatic carbon form nitrogen analyzer produced by SkalaR, USA.

[0066] 1.3 Data Processing

[0067] Excel 2021 was used to summarize and organize data, and SPSS 27.0 software was used to conduct analysis of variance for different factors. Origin 2022 was used to create charts, and the R4.4.2 software "linkET" package was used for mental test analysis, and the "Random Forest" package was used for random forest analysis.

[0068] result

[0069] 2.1 Impact of nitrogen fertilizer reduction and different green manure return methods on greenhouse gas emissions

[0070] 2.1.1 Main effect analysis of total soil CO2, CH4, and N2O emissions under reduced nitrogen fertilizer application and different green manure incorporation patterns showed that year significantly affected total soil CO2 and N2O emissions, but had no significant effect on total soil CH4 uptake. Both nitrogen application level and green manure incorporation pattern had significant effects on total soil CO2, CH4, and N2O emissions. The interaction effect between nitrogen application level and green manure incorporation pattern only significantly affected total soil CO2 emissions, but had no significant effect on total CH4 uptake and total N2O emissions. Furthermore, the interaction effect among year, nitrogen application level, and green manure incorporation pattern had no significant effect on total soil CO2, CH4, or N2O emissions (Table 3). During the two experimental years, under different nitrogen application levels, total soil CO2 and N2O emissions from N1 decreased by 8.7% and 27.9% compared with N2, respectively, and increased by 10.6% and 9.0%, respectively, compared with NO. Total soil CH4 uptake increased by 9.3% and 20.1%, respectively, compared with both nitrogen application levels. Under different green manure incorporation patterns, soil CO2 and N2O emissions decreased by 5.1% and 15.2%, respectively, compared with the RROS treatment, and increased by 1.6% and 7.2%, respectively, compared with the RROS treatment. Soil CH4 uptake showed no significant difference from the RROS treatment, but increased by 17.4% compared with the RROS treatment. The interaction between nitrogen application level and green manure incorporation pattern showed that soil CO2 and N2O emissions decreased by 3.2% and 28.1%, respectively, compared with the N2SDRR treatment, and decreased by 4.2% and 19.1%, respectively, compared with the N1RROS treatment. Soil CH4 uptake increased by 6.3% and 15.8%, respectively, compared with the N2SDRR treatment. Therefore, combining nitrogen fertilizer reduction with aboveground green manure incorporation can effectively increase CH4 uptake and reduce CO2 and N2O emissions in wheat fields.

[0071] Table 3 CO2 (kg hm -2 )、CH4(kg hm -2 )、N2O(kg hm -2 )

[0072]

[0073]

[0074] * represents P < 0.05, significant difference; ** represents P < 0.01, extremely significant difference; ns represents no significant difference, different lowercase letters represent significant differences among treatments (P < 0.05). The same below.

[0075] N2, N1, and N0 were respectively the traditional nitrogen fertilizer (N 225 kg·hm -2 ), nitrogen reduction by 30% (N 158kg·hm -2 ) and no nitrogen application (N 0kg·hm -2 ); RR, SDRR, and RROS represent aboveground removal and stubble return only, aboveground removal combined with stubble return, and full aboveground and stubble return, respectively; RRN2, RRN1, and RRN0 represent aboveground removal and stubble return only (RR) combined with traditional nitrogen application (N2), nitrogen reduction of 30% (N1), and no nitrogen application (NO), respectively; SDRRN2, SDRRN1, and SDRRNO represent aboveground removal combined with stubble return (SDRR) combined with traditional nitrogen application (N2), nitrogen reduction of 30% (N1), and no nitrogen application (NO), respectively; RROSN2, RROSN1, and RROSNO represent full aboveground and stubble return (RROS) combined with traditional nitrogen application (N2), nitrogen reduction of 30% (N1), and no nitrogen application (N0), respectively; the same below.

[0076] 2.1.2 Effects of nitrogen fertilizer reduction and different green manure incorporation methods on global warming potential The main effect analysis showed that year, nitrogen application level, green manure incorporation method, and the interaction effect between nitrogen application level and green manure incorporation method significantly affected global warming potential, while the interaction effect between year, nitrogen application level, and green manure incorporation method had no significant effect on global warming potential ( Figure 1 During the two experimental years, under different nitrogen application levels, soil GWP of N1 decreased by 6.1% compared with N2 and increased by 12.3% compared with NO. Under different green manure incorporation methods, soil GWP in the SDRR treatment decreased by 4.8% compared with RROS and increased by 2.3% compared with RR. The interaction between nitrogen application level and green manure incorporation method showed that soil GWP in the N1SDRR treatment decreased by 4.6% compared with N2SDRR and by 5.0% compared with N1RROS. Therefore, reducing nitrogen fertilizer application combined with incorporating the aboveground portion of green manure through the abdomen can effectively reduce the global warming potential of wheat farmland.

[0077] 2.2 Effects of nitrogen fertilizer reduction and different green manure return methods on wheat grain yield

[0078] The main effect analysis showed that year, nitrogen application level, green manure return method and the interaction effect between nitrogen application level and green manure return method significantly affected wheat grain yield, while the interaction effect between year, nitrogen application level and green manure return method had no significant effect on wheat grain yield ( Figure 3 Across the two experimental years, under different nitrogen application levels, wheat grain yield in the N1 treatment decreased by 28.7% compared with N2 and increased by 38.7% compared with NO. Under different green manure incorporation methods, grain yield in the SDRR treatment increased by 5.3% and 18.8% compared with RROS and RR, respectively. The interaction between nitrogen application level and green manure incorporation method showed that grain yield in the N1SDRR treatment was slightly lower than that in the N2SDRR treatment, but the difference was not significant. Furthermore, grain yield in the N1SDRR treatment increased by 8.8% and 4.1% compared with N1RR and N1RROS, respectively. Therefore, reducing nitrogen fertilizer application combined with incorporating the aboveground portion of green manure through the abdomen can effectively increase wheat grain yield.

[0079] 2.3 Effects of nitrogen fertilizer reduction and different green manure return methods on greenhouse gas emission intensity

[0080] The main effect analysis showed that year and nitrogen application level had significant effects on greenhouse gas emission intensity, while green manure return method and the interaction effect between the two had no significant effects on greenhouse gas emission intensity. The interaction effect among year, nitrogen application level and green manure return method had no significant effects on greenhouse gas emission intensity ( Figure 3 ). During the two experimental years, under different nitrogen application levels, the greenhouse gas emission intensity of the N1 treatment showed no significant difference from that of N2, and was 19.6% lower than that of NO. Under different green manure incorporation methods, the greenhouse gas emission intensity of the SDRR treatment was 6.9% and 18.8% lower than that of RROS and RR, respectively. Under the interaction of nitrogen application level and green manure incorporation method, the greenhouse gas emission intensity of the N1SDRR treatment was 8.5% and 14.6% lower than that of N2SDRR and N1RROS, respectively. Therefore, reducing nitrogen fertilizer application combined with incorporating the aboveground part of green manure into the field can effectively reduce the greenhouse gas emission intensity of wheat farmland.

[0081] 2.4 Effects of reduced nitrogen fertilizer application and different green manure incorporation methods on soil physicochemical properties and soil enzyme activities 2.4.1 Effects of reduced nitrogen fertilizer application and different green manure incorporation methods on soil physicochemical properties

[0082] The main effect analysis showed that year, nitrogen application level, green manure return method and their interaction effect had significant effects on soil physical and chemical indices (except bulk density), while the interaction effect among year, nitrogen application level and green manure return method had no significant effect on soil physical and chemical indices (Table 4).

[0083] Table 4 Interaction analysis of the effects of nitrogen application level and green manure return method on soil physical and chemical properties

[0084]

[0085] In the two experimental years, under different nitrogen application levels, the contents of soil organic matter, ammonium nitrogen, and nitrate nitrogen in N1 decreased by 4.2%, 7.0%, and 7.8% respectively compared with N2, and increased by 16.7%, 6.3%, and 7.6% respectively compared with NO. Figure 4 ). The soil bulk density and pH content of the N1 treatment showed no significant differences from those of the N2 treatment. Under different green manure incorporation methods, the soil organic matter and ammonium nitrogen contents of the SDRR treatment increased by 9.1% and 17.4% respectively compared with those of the RROS treatment, but the nitrate nitrogen content decreased by 8.9%; and increased by 23.5% and 22.3% respectively compared with those of the RR treatment. Under the interaction between nitrogen application level and green manure incorporation method, the soil bulk density, organic matter, ammonium nitrogen, and nitrate nitrogen contents of the N1SDRR treatment decreased by 4.4%, 3.1%, 3.7%, and 3.0% respectively compared with those of the N2SDRR treatment; the soil organic matter and ammonium nitrogen contents increased by 9.1% and 22.8% respectively compared with those of the N1RROS treatment, but the soil bulk density and nitrate nitrogen contents decreased by 4.1% and 10.0% respectively. Therefore, reducing nitrogen fertilizer application combined with incorporating the aboveground part of green manure into the field is beneficial to improving the physical and chemical properties of soil in wheat farmland.

[0086] 2.4.2 Effects of nitrogen fertilizer reduction and different green manure return methods on soil enzyme activities

[0087] The main effect analysis showed that year and nitrogen application level significantly affected the activities of soil urease, sucrase, nitrite reductase and nitrate reductase; green manure return method had a significant effect on the activities of soil urease, sucrase and nitrate reductase, but had no significant effect on the activity of soil nitrite reductase; the interaction effect between nitrogen application level and green manure return method only had a significant effect on the activity of soil nitrate reductase, but had no significant effect on the activities of soil urease, sucrase and nitrite reductase; the interaction effect between year, nitrogen application level and green manure return method had no significant effect on the soil enzyme activity indicators ( Figure 5During the two experimental years, under different nitrogen application levels, the activities of soil nitrite reductase and nitrate reductase in the N1 treatment decreased by 3.2% and 3.8%, respectively, compared with those in the N2 treatment, but the sucrase activity increased by 6.2% compared with that in the N2 treatment. The activities of soil sucrase, urease, nitrite reductase, and nitrate reductase increased by 18.2%, 9.0%, 9.3%, and 12.9%, respectively, compared with those in the N0 treatment. Under different green manure incorporation methods, the activities of soil nitrite reductase and nitrate reductase in the SDRR treatment decreased by 12.1% and 5.2%, respectively, compared with those in the RROS treatment, but the urease activity increased by 7.8%. The soil urease activity increased by 6.2%, but the soil nitrite reductase activity decreased by 7.0%. The interaction between nitrogen application level and green manure incorporation method revealed that soil nitrite reductase and nitrate reductase activities decreased by 8.8% and 9.4%, respectively, in the N1SDRR treatment compared with those in the N2SDRR treatment, but soil urease activity increased by 5.8%. Compared with the N1RR0S treatment, soil sucrase and urease activities increased by 3.2% and 7.8%, respectively, but soil nitrite reductase and nitrate reductase activities decreased by 11.9% and 5.7%, respectively. Therefore, combining nitrogen reduction with incorporation of green manure aboveground portions is beneficial for improving soil enzyme activities in wheat fields.

[0088] 2.5 Comprehensive analysis of soil characteristics and global warming potential, grain yield, and greenhouse gas emission intensity

[0089] Correlation analysis showed that organic matter, nitrate nitrogen, ammonium nitrogen content, and sucrase, urease, and nitrate reductase activities were significantly positively correlated with grain yield, global warming potential, and greenhouse gas emission intensity, while bulk density and nitrite reductase were significantly negatively correlated with grain yield, global warming potential, and greenhouse gas emission intensity. Among them, organic matter, ammonium nitrogen, nitrate nitrogen, sucrase, and urease explained a large amount of wheat grain yield (0.5≤Mantel's r), organic matter, nitrate nitrogen, and urease explained a large amount of global warming potential (0.5≤Mantel's r), while organic matter, ammonium nitrogen, nitrate nitrogen, sucrase, urease, and nitrate reductase activities explained a large amount of greenhouse gas emission intensity (0.5≤Mantel's r)( Figure 6 a). Further analysis using the random forest model revealed that the main influencing factors of greenhouse gas emission intensity were sucrase, grain yield, and organic matter content, with a total contribution rate of 48% ( Figure 6 b). In summary, nitrogen fertilizer reduction combined with green manure incorporation enhances soil carbon sequestration capacity and optimizes nutrient use efficiency by regulating soil properties such as organic matter and sucrase activity. It also reduces global warming potential and increases grain yield, thereby reducing greenhouse gas emissions, providing a scientific basis for greenhouse gas emission reduction.

[0090] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for returning green manure and feed to farmland for both fertilizer saving and emission reduction, characterized by: The steps include: S1, sow wheat in mid-March and harvest in late July; S2. Green manure is sown after wheat harvest, using a mixture of pea and barley; S3. After frost in late October, graze on the green manure plots, and the aboveground part of the green manure will be naturally eaten and converted into sheep manure, which will be returned to the fields; S4. In early November, deep plow the green manure plot and bury the sheep manure and green manure roots and stubble into the soil.

2. A method for returning green manure and feed to farmland for both fertilizer saving and emission reduction as claimed in claim 1, characterized in that: In step S1, the sowing density of wheat is 6.75 million grains / hm2. 2 , adopt row sowing method, with row spacing of 12cm.

3. A method for returning green manure and feed to farmland for both fertilizer saving and emission reduction as claimed in claim 1, characterized in that: In step S2, green manure is sown in early August at the latest, and the sowing rate of mixed sowing of arrow pea and highland barley is 180kg / hm2 respectively. 2 and 52.5kg / hm 2 .

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