Green manure returning method suitable for arid and semi-arid regions

Abstract

The invention discloses a green manure returning method suitable for arid and semi-arid regions, and belongs to the technical field of green manure returning. Green manure crops are harvested to prepare slow-release green manure to be applied to soil, and the slow-release green manure can quickly release part of water and nutrients after entering the soil; the rest of the slow-release green manure is continuously decomposed in the soil to release the nutrients, and meanwhile, water in the soil is effectively absorbed and retained, so that better growth conditions are provided for crop growth, the crop yield is ensured, and the crop yield is improved. The method for returning the green manure to the field has important significance on increasing the yield of crops in arid and semi-arid regions.

Description

Technical Field

[0001] The invention relates to the technical field of returning green manure to fields, and in particular to a method for returning green manure to fields suitable for arid and semi-arid areas. Background Art

[0002] In the history of China's agricultural development, chemical fertilizers have made great contributions to ensuring food security, but blind and excessive application of chemical fertilizers has not increased crop yields. Instead, it has caused a certain degree of damage to soil functions, leading to ecological and environmental problems such as soil quality decline, water eutrophication, and greenhouse gas emissions. Therefore, reducing the use of chemical fertilizers and pesticides and increasing the use of organic materials is considered an effective way to achieve green agricultural production.

[0003] Green manure, as a traditional organic material, is an environmentally friendly crop variety. It is of great significance in improving soil, conserving water and soil, suppressing weeds, and improving crop productivity. There is a certain period of fallow period between the harvest of grain crops and the sowing of the next season. Planting cover crops during the fallow period can not only cover the surface to protect the soil, but also return it to the field as green manure to improve soil fertility and improve soil physical and chemical properties. The conventional method of returning green manure to the field is to directly turn the green manure over and return it to the field. The decomposition rate of green manure in the soil is slow, and water and nutrients cannot be released into the soil in time. In arid and semi-arid areas, the soil is relatively poor and water is scarce. Planting green manure is prone to pre-emptive competition for water and nutrients. The green manure has a slow decomposition rate after being directly turned over and returned to the field, and cannot release water and nutrients in time, which in turn causes water and nutrient deficiencies in subsequent crops, resulting in reduced yields.

[0004] Therefore, there is a need to find a method for returning green manure to the fields that is suitable for arid and semi-arid areas to solve the problem that green manure planting in arid and semi-arid areas is prone to pre-emptive competition for water and nutrients, and the green manure has a slow decomposition rate after being directly turned over and returned to the fields, and water and nutrients cannot be released in time, resulting in insufficient water and nutrient supply to subsequent crops and reduced yields. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for returning green manure to the field that is suitable for arid and semi-arid areas. Green manure planting in arid and semi-arid areas is prone to cause pre-entry competition for water and nutrients, and the green manure has a slow decomposition rate after being directly turned over and returned to the field, and water and nutrients cannot be released in time, resulting in insufficient water and nutrient supply to subsequent crops and resulting in reduced yields.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A method for returning green manure to fields suitable for arid and semi-arid areas, the method being as follows:

[0008] (1) harvesting the green manure crops, crushing and beating the crops, filtering and separating the crops to obtain a liquid and a residue for later use;

[0009] (2) gelatin is dissolved in water to prepare a 10 wt % gelatin solution, isopropanolamine is added, stirred evenly, and then spray-dried to obtain gelatin-embedded microparticles; xanthan gum is dissolved in water to prepare a 2 wt % xanthan gum solution, the pH of the xanthan gum solution is adjusted to 5, nano-silicon dioxide is added, the reaction is stirred at room temperature for 3-4 hours, and then the temperature is raised to 50-60° C. and stirred for 1-2 hours. After the reaction is completed, the residue, gelatin-embedded microparticles, and ammonium bicarbonate are added in sequence and mixed evenly, and then the mixture is put into a granulator for granulation to obtain granular fertilizer, and the granular fertilizer is dried at 50° C. to a moisture content of ≤15% to obtain porous granular fertilizer, which is set aside;

[0010] (3) adding water to dissolve sodium alginate to prepare a 15 wt% sodium alginate solution, then heating to 50-60° C. and adding glyoxylic acid to stir and react for 4-6 hours, adding the feed liquid after the reaction is completed and mixing evenly, then adding porous granular fertilizer and slowly stirring and mixing for 20-30 minutes to obtain a mixture, adding 20 wt% calcium chloride solution to the mixture and stirring to gel the sodium alginate in the mixture, and then putting the mixture into a granulator for granulation to obtain a slow-release green fertilizer;

[0011] (4) Apply the slow-release green manure to the soil surface, then till the soil to mix it into the surface soil. When planting the next crop, the soil can be turned over and the planting can begin.

[0012] In arid and semi-arid areas, due to the poor soil and water shortage, the first-entry competition between nutrients and water is easy to occur when planting green manure. Under the conventional method, the green manure is directly turned over and returned to the field, and the decomposition rate is slow, and then the water and nutrients cannot be released in time, resulting in the failure to supply water and nutrients in time when the subsequent crops are planted, which can easily cause a decrease in crop yield. Therefore, the present invention prepares the slow-release green manure after harvesting the green manure and applies it to the soil to ensure the timely supply of water and nutrients for the subsequent crops, and at the same time improves the physical and chemical properties of the soil to promote the good growth of the subsequent crops.

[0013] Specifically, the present invention crushes and pulps the harvested green manure crops and separates them to obtain a liquid and a residue, and then mixes the residue with a binder such as xanthan gum and nano-silicon dioxide to prepare a porous granular fertilizer; sodium alginate is mixed with the liquid, added to the porous granular fertilizer, and evenly mixed, and then calcium chloride is added for gelation, and then granulation is performed to obtain a slow-release green manure. In this process, the sodium alginate gels to wrap the liquid and fill it inside the porous granular fertilizer and wrap it on the surface of the porous granular fertilizer. After being applied to the soil, the sodium alginate gel embeds and fixes the moisture and nutrients of the liquid and releases them into the soil to first replenish the moisture and nutrients in the soil, and then the remaining porous granular fertilizer continues to decompose in the soil to release the remaining nutrients, thereby ensuring the timely supply of moisture and nutrients for subsequent crops and enabling the nutrients in the green manure to be efficiently utilized.

[0014] In order to allow the moisture and nutrients in the sodium alginate gel embedding solution to be released more quickly into the soil to supplement the moisture and nutrients competitively absorbed during green manure planting, the present invention adds glyoxylic acid and sodium alginate to react, and the glyoxylic acid is combined with the sodium alginate molecular chain to change its chemical stability, thereby accelerating the degradation rate of the sodium alginate gel in the soil, so that the moisture and nutrients in the sodium alginate embedding solution can be released into the soil for rapid replenishment as the sodium alginate gel is rapidly degraded.

[0015] The soil in arid and semi-arid areas is poor in nutrients and has low water content. The number and activity of microorganisms in the soil are also low, which will cause the degradation of the remaining granular fertilizer to be slow. Therefore, the present invention uses gelatin to embed isopropanolamine to prepare gelatin-embedded microparticles and mix them into porous granular fertilizer. The gelatin is rapidly degraded in the soil to release isopropanolamine. The isopropanolamine then acts on the chemical bonds formed by the combination of xanthan gum and nano-silicon dioxide to break them, thereby disintegrating the granular fertilizer structure and becoming loose. Xanthan gum has good stability and can exist stably in the soil for a long time. After the granular fertilizer structure is loose, the xanthan gum can be used as a fertilizer. The original gum can fully expand and absorb and retain a large amount of water, thereby improving the water retention of the soil and improving the soil properties. At the same time, xanthan gum and gelatin can provide better nutrition for microorganisms in the soil. Therefore, the granular fertilizer after the structure is disintegrated and loosened can provide better water and nutrient supply for microorganisms, allowing microorganisms in the soil to colonize in the loose granular fertilizer position and proliferate and grow well, so as to accelerate the decomposition of the granular fertilizer and better provide nutrients for subsequent crops. The decomposition of granular fertilizer improves soil fertility while improving soil water retention, providing better conditions for the growth of subsequent crops.

[0016] Furthermore, the green manure crops in step (1) are any one or two of beans, sudan grass, peas, alfalfa, oats, hairy vetch, and astragalus.

[0017] Furthermore, in the step (2), the mass ratio of gelatin solution to isopropanolamine is (2.5-4.5): (0.02-0.04).

[0018] Furthermore, in the step (2), the mass ratio of xanthan gum solution, nano-silicon dioxide, slag, gelatin-embedded microparticles, and ammonium bicarbonate is (8-10): (1-2): (8-10): (0.2-0.4): (0.1-0.2).

[0019] Furthermore, in the step (2), the particle size of the ammonium bicarbonate is 100 μm.

[0020] Furthermore, in the step (2), the particle size of the granulated fertilizer is 3-4 mm.

[0021] Furthermore, in step (3), the mass ratio of the sodium alginate solution, glyoxylic acid, slurry, porous granular fertilizer and calcium chloride solution is (10-15): (0.1-0.2): (25-35): (10-15): (0.2-0.5).

[0022] Furthermore, in step (3), the granulation particle size is 5-8 mm.

[0023] Furthermore, in step (4), the rotary tillage depth is 5-10 cm, and the tillage depth is 15-25 cm.

[0024] Beneficial effects:

[0025] The present invention crushes and pulps the green manure and separates it into liquid and residue. The liquid and residue are further prepared into slow-release green manure and applied to the soil. The slow-release green manure can quickly release part of the water and nutrients to supplement the water and nutrients absorbed competitively during the planting of the green manure, ensure the supply of water and nutrients in the early stage of planting the subsequent crops, and then the remaining residue continues to decompose in the soil to improve the soil fertility, while improving the soil's water absorption and water retention capacity, better ensure the good growth of crops, and increase crop yields. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : It is a picture of the growth status of Sudan grass, a green manure crop returned to the field of the present invention;

[0027] Figure 2 : This is a picture of the growth status of winter wheat in the green period of experimental group 1 in the experiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings:

[0029] The present invention discloses a method for returning green manure to fields suitable for arid and semi-arid areas. The specific method is to first prepare the green manure into slow-release green manure and then apply it to the soil according to a specific method for returning it to the fields. Therefore, the present invention first prepares the green manure into slow-release green manure, as shown below.

[0030] Example 1: Preparation of slow-release green manure

[0031] (1) harvesting the green manure crop Sudan grass, crushing and beating the grass, filtering and separating the grass liquid and the grass residue for later use;

[0032] (2) gelatin was dissolved in water to prepare 3.5 kg of 10 wt% gelatin solution, and then 0.03 kg of isopropanolamine was added and stirred evenly, and spray-dried under the conditions of an inlet air temperature of 150° C., an outlet air temperature of 80° C., and a feed flow rate of 20 mL / min to obtain gelatin-embedded microparticles; xanthan gum was dissolved in water to prepare 9 kg of 2 wt% xanthan gum solution, and 1.5 kg of nano-silicon dioxide was added after adjusting the pH of the xanthan gum solution to 5, and the mixture was stirred and reacted at room temperature for 3.5 h, and then the mixture was heated to 55° C. and stirred and reacted for 1.5 h. After the reaction was completed, 9 kg of slag, 0.3 kg of gelatin-embedded microparticles, and 0.15 kg of ammonium bicarbonate with a particle size of 100 μm were added in sequence, mixed evenly, and then placed in a granulator to prepare granular fertilizer with a particle size of about 3 mm, and the granular fertilizer was dried at 50° C. until the moisture content was about 10% to obtain porous granular fertilizer, which was set aside;

[0033] (3) Sodium alginate is dissolved in water to prepare 12 kg of 15 wt% sodium alginate solution, and then the temperature is raised to 55° C. and 0.15 kg of glyoxylic acid is added and stirred for reaction for 5 h. After the reaction is completed, 30 kg of the feed liquid is added and mixed evenly, and then 12 kg of porous granular fertilizer is added and slowly stirred for 25 min to obtain a mixture, and 0.3 kg of 20 wt% calcium chloride solution is added to the mixture to gel the sodium alginate in the mixture, and then the mixture is put into a granulator to prepare granules with a particle size of about 6 mm to obtain a slow-release green fertilizer.

[0034] Example 2: Preparation of slow-release green manure

[0035] (1) harvesting the green manure crop Sudan grass, crushing and beating the grass, filtering and separating the grass liquid and the grass residue for later use;

[0036] (2) gelatin is dissolved in water to prepare 2.5 kg of 10 wt% gelatin solution, then 0.02 kg of isopropanolamine is added and stirred evenly, and spray-dried under the conditions of an inlet air temperature of 150° C., an outlet air temperature of 80° C., and a feed flow rate of 20 mL / min to obtain gelatin-embedded microparticles; xanthan gum is dissolved in water to prepare 8 kg of 2 wt% xanthan gum solution, 1 kg of nano-silicon dioxide is added after the pH of the xanthan gum solution is adjusted to 5, and the mixture is stirred and reacted at room temperature for 3 h, then heated to 50° C. and stirred and reacted for 1 h. After the reaction is completed, 8 kg of slag, 0.2 kg of gelatin-embedded microparticles, and 0.1 kg of ammonium bicarbonate with a particle size of 100 μm are added in sequence, mixed evenly, and then placed in a granulator to prepare granular fertilizer with a particle size of about 3 mm, and the granular fertilizer is dried at 50° C. until the moisture content is about 10% to obtain porous granular fertilizer, which is set aside;

[0037] (3) Sodium alginate is dissolved in water to prepare 10 kg of 15 wt% sodium alginate solution, and then the temperature is raised to 50°C and 0.1 kg of glyoxylic acid is added and stirred for reaction for 4 hours. After the reaction is completed, 25 kg of the feed liquid is added and mixed evenly, and then 10 kg of porous granular fertilizer is added and slowly stirred for 20 minutes to obtain a mixture, and 0.2 kg of 20 wt% calcium chloride solution is added to the mixture to gel the sodium alginate in the mixture, and then the mixture is put into a granulator to prepare granules with a particle size of about 6 mm to obtain a slow-release green fertilizer.

[0038] Example 3: Preparation of slow-release green manure

[0039] (1) harvesting the green manure crop Sudan grass, crushing and beating the grass, filtering and separating the grass liquid and the grass residue for later use;

[0040] (2) gelatin is dissolved in water to prepare 4.5 kg of 10 wt% gelatin solution, then 0.04 kg of isopropanolamine is added and stirred evenly, and spray-dried under the conditions of an inlet air temperature of 150° C., an outlet air temperature of 80° C., and a feed flow rate of 20 mL / min to obtain gelatin-embedded microparticles; xanthan gum is dissolved in water to prepare 10 kg of 2 wt% xanthan gum solution, 2 kg of nano-silicon dioxide is added after the pH of the xanthan gum solution is adjusted to 5, and the mixture is stirred and reacted at room temperature for 4 h, then heated to 60° C. and stirred and reacted for 2 h. After the reaction is completed, 10 kg of slag, 0.4 kg of gelatin-embedded microparticles, and 0.2 kg of ammonium bicarbonate with a particle size of 100 μm are added in sequence, mixed evenly, and then placed in a granulator to prepare granular fertilizer with a particle size of about 3 mm, and the granular fertilizer is dried at 50° C. until the moisture content is about 10% to obtain porous granular fertilizer, which is set aside;

[0041] (3) Sodium alginate is dissolved in water to prepare 15 kg of 15 wt% sodium alginate solution, and then the temperature is raised to 60°C and 0.2 kg of glyoxylic acid is added and stirred for reaction for 4 hours. After the reaction is completed, 35 kg of the feed liquid is added and mixed evenly, and then 15 kg of porous granular fertilizer is added and slowly stirred for 30 minutes to obtain a mixture, and 0.5 kg of 20 wt% calcium chloride solution is added to the mixture to gel the sodium alginate in the mixture, and then the mixture is put into a granulator to prepare granules with a particle size of about 6 mm to obtain a slow-release green fertilizer.

[0042] Comparative Example 1: Preparation of slow-release green manure

[0043] In contrast to Example 1, the only difference is that in the preparation of the slow-release green manure in Comparative Example 1, gelatin particles are not added in step (2), as shown below:

[0044] (1) Same as Example 1;

[0045] (2) dissolving xanthan gum in water to prepare 9 kg of 2 wt% xanthan gum solution, adjusting the pH of the xanthan gum solution to 5, adding 1.5 kg of nano-silicon dioxide, stirring and reacting at room temperature for 3.5 hours, then heating to 55° C. and stirring and reacting for 1.5 hours, and after the reaction is completed, adding 9 kg of slag and 0.15 kg of ammonium bicarbonate with a particle size of 100 μm in sequence, mixing evenly, and putting into a granulator to prepare granular fertilizer with a particle size of about 3 mm, drying the granular fertilizer at 50° C. until the moisture content is about 10% to obtain porous granular fertilizer, and setting aside;

[0046] (3) Same as Example 1.

[0047] Comparative Example 2: Preparation of slow-release green manure

[0048] In contrast to Example 1, the only difference is that in Comparative Example 2, xanthan gum is not used in the preparation of the slow-release green manure, but gum arabic is used, as shown below:

[0049] (1) Same as Example 1;

[0050] (2) gelatin was dissolved in water to prepare 3.5 kg of 10 wt% gelatin solution, and then 0.03 kg of isopropanolamine was added and stirred evenly, and spray-dried under the conditions of an inlet air temperature of 150° C., an outlet air temperature of 80° C., and a feed flow rate of 20 mL / min to obtain gelatin-embedded microparticles; arabic gum was dissolved in water to prepare 9 kg of 2 wt% arabic gum, and 1.5 kg of nano-silicon dioxide was added after adjusting the pH of the arabic gum to 5, and the mixture was stirred and reacted at room temperature for 3.5 h, and then the mixture was heated to 55° C. and stirred and reacted for 1.5 h. After the reaction was completed, 9 kg of slag, 0.3 kg of gelatin-embedded microparticles, and 0.15 kg of ammonium bicarbonate with a particle size of 100 μm were added in sequence, mixed evenly, and then placed in a granulator to prepare granular fertilizer with a particle size of about 3 mm, and the granular fertilizer was dried at 50° C. until the moisture content was about 10% to obtain porous granular fertilizer, which was set aside;

[0051] (3) Same as Example 1.

[0052] Comparative Example 3: Preparation of slow-release green manure

[0053] In contrast to Example 1, the only difference is that in the preparation of the slow-release green manure in Comparative Example 3, glyoxylic acid is not added to treat the sodium alginate in step (3), as shown below:

[0054] (1)-(2) are the same as in Example 1;

[0055] (3) Sodium alginate is dissolved in water to prepare 12 kg of 15 wt% sodium alginate solution, 30 kg of the feed liquid is added and mixed evenly, 12 kg of porous granular fertilizer is added and slowly stirred for 25 min to obtain a mixture, 0.3 kg of 20 wt% calcium chloride solution is added to the mixture to gel the sodium alginate in the mixture, and then the mixture is put into a granulator to prepare granules with a particle size of about 6 mm to obtain a slow-release green fertilizer.

[0056] Comparative Example 4: Preparation of slow-release green manure

[0057] In contrast to Example 1, the only difference is that in the preparation of the slow-release green manure in Comparative Example 4, gelatin is used instead of sodium alginate in step (3), as shown below:

[0058] (1)-(2) are the same as in Example 1;

[0059] (3) Dissolve gelatin in water to prepare 12 kg of 15 wt% gelatin solution, then heat to 55°C and add 0.15 kg of glyoxylic acid to stir and react for 5 hours. After the reaction is completed, add 30 kg of liquid and mix evenly. Then add 12 kg of porous granular fertilizer and slowly stir and mix for 25 minutes to obtain a mixture. Add 0.3 kg of 20 wt% calcium chloride solution to the mixture to gel the sodium alginate in the mixture, and then put it into a granulator to prepare granules with a particle size of about 6 mm to obtain a slow-release green fertilizer.

[0060] Embodiment 4: Green manure returning method

[0061] The slow-release green manure prepared in Example 1 is further returned to the field, specifically as follows:

[0062] Apply the slow-release green manure to the soil surface, then till the soil to a depth of about 6 cm to mix the slow-release green manure into the surface soil. When planting the next crop, winter wheat, turn the soil to a depth of about 20 cm and plant it according to the conventional method.

[0063] Experiment: Experiment on the effect of returning slow-release green manure to the field

[0064] 1. Experimental method: The slow-release green manure prepared in Example 1 and Comparative Examples 1-4 was returned to the field to detect the effect of returning the green manure to the field. The experiment was carried out at the National Field Scientific Observation and Research Station of Farmland Ecosystem in Changwu, Shaanxi Province. A block area was selected as the experimental area. The initial soil moisture content was 45.2%, the alkaline nitrogen content was 41.5 mg / kg, and the organic matter content was 8.6 g / kg. The experimental area was divided into 7 areas, each with an area of ​​6×10 m, corresponding to the experimental group 1, the control group 1-5 and the blank control group, respectively. The method of returning the green manure to the field in each group is as follows:

[0065] Experimental group 1: slow-release green manure was prepared by the method of Example 1 and returned to the field according to the method of Example 4;

[0066] Control groups 1-4: The slow-release green manures prepared in comparative examples 1-4 were respectively used and returned to the field according to the method of example 4;

[0067] Control group 5: slow-release green manure was prepared by the method of Example 1, and the tillage depth after application to the soil was 15 cm. The remaining steps were the same as those of Example 4;

[0068] Blank control: The green manure alfalfa was not prepared into slow-release green manure, but was directly turned over and returned to the field.

[0069] 2. Result detection: On the 15th day after the green manure was returned to the field, the soil moisture content, alkaline nitrogen content, and organic matter content (recorded as moisture content A, alkaline nitrogen content A, and organic matter content A) of the soil layer at a depth of 0-20 cm were detected. 16 days after the green manure was returned to the field, the field was plowed and winter wheat was planted according to the conventional method. The same method was used for management and maintenance. 30 days after the winter wheat was planted, the soil moisture content, alkaline nitrogen content, and organic matter content (recorded as moisture content B, alkaline nitrogen content B, and organic matter content B) of the soil layer at a depth of 0-20 cm were measured again. The yield of winter wheat in each group was recorded, and the data obtained are shown in Table 1:

[0070] Table 1

[0071]

[0072]

[0073] According to the data analysis in Table 1:

[0074] (1) The slow-release green manure prepared by the present invention can quickly release some nutrients after being applied to the soil. After 15 days of application, the soil water content increased significantly, and the alkaline nitrogen and organic matter content also increased to a high extent. When the winter wheat was planted for 30 days, the organic matter content increased significantly, indicating that the decomposition rate of the granular fertilizer in the soil was high and a large amount of nutrients were obtained.

[0075] (2) In the control group 1, gelatin was not added to the green manure to prepare the slow-release green manure, which lacked the effect of isopropanolamine in the embedded particles. The granular fertilizer had a firm structure and was difficult to decompose. The expansion performance of xanthan gum was inhibited, and the water absorption and water retention performance was reduced. In addition, the nutrients provided by gelatin were missing, which resulted in a reduction in the decomposition ability of microorganisms and a relatively small increase in nutrients.

[0076] (3) In the control group 2, gum arabic was used to prepare the slow-release green manure, which quickly decomposed in the soil and lost its ability to absorb and retain water, so the moisture content of the soil decreased significantly in the later period. In the control group 3, no glyoxylic acid was added to treat the sodium alginate, and the decomposition rate of the sodium alginate slowed down, resulting in a decrease in the release of water and nutrients.

[0077] (4) In the control group 5, when the slow-release green manure was returned to the field, the depth of rotary tillage was large and the nutrients entered the lower soil layer. Although the average moisture and nutrient content of the soil layer at a depth of 0-20 cm was high, the small amount of moisture and nutrients used in the initial stage also led to a significant reduction in winter wheat yield.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A method for returning green manure to fields suitable for arid and semi-arid areas, characterized in that: The method is as follows: (1) harvesting the green manure crops, crushing and beating the crops, filtering and separating the crops to obtain a liquid and a residue for later use; (2) gelatin is dissolved in water to prepare a 10 wt % gelatin solution, isopropanolamine is added, stirred evenly, and then spray-dried to obtain gelatin-embedded microparticles; xanthan gum is dissolved in water to prepare a 2 wt % xanthan gum solution, the pH of the xanthan gum solution is adjusted to 5, nano-silicon dioxide is added, the reaction is stirred at room temperature for 3-4 hours, and then the temperature is raised to 50-60° C. and stirred for 1-2 hours. After the reaction is completed, the residue, gelatin-embedded microparticles, and ammonium bicarbonate are added in sequence and mixed evenly, and then the mixture is put into a granulator for granulation to obtain granular fertilizer, and the granular fertilizer is dried at 50° C. to a moisture content of ≤15% to obtain porous granular fertilizer, which is set aside; (3) Sodium alginate is dissolved in water to prepare a 15 wt% sodium alginate solution, and then the temperature is raised to 50-60° C. and glyoxylic acid is added and stirred for reaction for 4-6 hours. After the reaction is completed, the feed liquid is added and mixed evenly, and then porous granular fertilizer is added and slowly stirred for 20-30 minutes to obtain a mixture, and 20 wt% calcium chloride solution is added to the mixture and stirred to gel the sodium alginate in the mixture, and then the mixture is put into a granulator for granulation to obtain a slow-release green fertilizer; (4) Apply the slow-release green manure to the soil surface, then till the soil to mix it into the surface soil. When planting the next crop, the soil can be tilled and then planted.

2. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 1, characterized in that: The green manure crops are any one or two of beans, Sudan grass, peas, alfalfa, oats, hairy vetch and astragalus.

3. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 2, characterized in that: The mass ratio of gelatin solution to isopropanolamine in the step (2) is (2.5-4.5): (0.02-0.04).

4. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 3, characterized in that: In the step (2), the mass ratio of xanthan gum solution, nano-silicon dioxide, residue, gelatin-embedded microparticles, and ammonium bicarbonate is (8-10): (1-2): (8-10): (0.2-0.4): (0.1-0.2).

5. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 4, characterized in that: The particle size of the ammonium bicarbonate in the step (2) is 100 μm.

6. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 5, characterized in that: The particle size of the granulated fertilizer in step (2) is 3-4 mm.

7. The method for returning green manure to fields in arid and semi-arid areas according to claim 6, characterized in that: In the step (3), the mass ratio of the sodium alginate solution, glyoxylic acid, slurry, porous granular fertilizer and calcium chloride solution is (10-15): (0.1-0.2): (25-35): (10-15): (0.2-0.5).

8. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 7, characterized in that: The granulation particle size in step (3) is 5-8 mm.

9. The method for returning green manure to fields suitable for arid and semi-arid areas according to claim 8, characterized in that: In the step (4), the rotary tillage depth is 5-10 cm, and the tillage depth is 15-25 cm.

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