Preparation method of water-retaining compound organic fertilizer

Abstract

The invention discloses a preparation method of a water-retaining compound organic fertilizer, and relates to a preparation method of a compound organic fertilizer. The invention aims to solve the problem that the existing organic fertilizer has poor water retention or water storage capacity after improving soil. The functional component is introduced while the acrylic acid and the acrylamide are copolymerized, and the micron-sized primary water-retaining compound organic fertilizer is introduced at the same time, so that a complex interpenetrating polymer network structure is formed among the acrylic acid, the acrylamide, the functional component and the micron-sized primary water-retaining compound organic fertilizer, and molecular chains are interpenetrated; the stability and the water retention capacity of the organic fertilizer are improved inside the organic fertilizer; the organic fertilizer is applied to be combined with soil particles, the granular structure of soil is improved, the porosity of the soil is increased, formation of the granular structure is promoted, soil hardening is reduced, the volume weight of the soil is effectively reduced, and the fertility of the soil is improved. In addition, the dosage of the acrylic acid-acrylamide copolymer is remarkably reduced, the cost is remarkably reduced, and the method has relatively good practicability and can be popularized.

Description

Technical Field

[0001] The present invention relates to a preparation method of a compound organic fertilizer. Background Art

[0002] The black soil area is the main grain production base in China. However, due to long-term high-intensity utilization, unreasonable farming methods, and excessive use of chemical fertilizers and pesticides, the black soil layer has become thinner, the soil structure has been damaged, and the soil fertility and water storage and moisture retention capabilities have declined. This has seriously affected the soil quality and crop yields in China and poses a severe challenge to the sustainable development of agriculture in China. Therefore, it is urgent for us to take effective measures to protect and manage black soil resources. At the same time, drought disasters are one of the most serious natural disasters affecting the land. Due to the uneven distribution of water resources in time and space, the critical period for crop growth does not match the distribution of annual precipitation, resulting in significant seasonal drought characteristics in the agricultural field. Once it occurs, the impact and influence on the social and economic system, especially on agricultural production, are extremely significant and cannot be underestimated. In the past 20 years, the drought-affected area of crops in China has accounted for more than 9.0% of the national sown area. The Northeast region is the grain production base in China. There are approximately 294 million mu of cultivated land in the typical black soil area in the Northeast region of China, accounting for 15.4% of the national cultivated land area. However, after the above drought disasters, long-term high-intensity utilization, and unreasonable farming, some black lands have become "thin" and "less", with serious soil compaction and degradation, reduced soil fertility and productivity, and weakened resistance to drought and cold damage. Therefore, it is necessary to explore an agricultural management measure that can improve soil fertility, increase soil nutrient content, and enhance the drought resistance and moisture retention ability of black soil in the Northeast region.

[0003] Organic fertilizers mainly include commercial organic fertilizers, bio-organic fertilizers, crop straws, green manures, livestock and poultry manure, etc. These fertilizers contain rich organic matter, macronutrients such as nitrogen, phosphorus, and potassium, as well as various trace elements, which are essential nutrient sources for plant growth. At the same time, organic fertilizers also have good physical and chemical properties and play a crucial role in soil improvement projects, such as improving soil structure, increasing soil porosity, and enhancing soil water retention and fertilizer retention. However, the water retention or water storage capacity is limited after the soil is improved by single organic fertilizer. Superabsorbent resins, which have been widely studied by scientific researchers in recent years, are polymer materials that can absorb dozens or even hundreds of times their own weight in water and have significant effects in fields such as drought resistance and moisture retention, soil solidification and improvement. However, the organic fertilizers composed of such superabsorbent resins have high costs and poor practicability and cannot be better applied to agricultural production practices. Summary of the Invention

[0004] In order to solve the problem that the existing organic fertilizer has poor water retention or water storage capacity after improving the soil, the present invention provides a preparation method of a water-retaining compound organic fertilizer.

[0005] The preparation method of the water-retaining composite organic fertilizer of the present invention is carried out according to the following steps:

[0006] Step 1, prepare a modified composite filler;

[0007] The preparation method of the modified composite filler is: mix dimethyl silicone oil, attapulgite and humic acid, then place them in a reaction kettle at 350-360°C for reaction for 80-90 minutes. After the reaction is completed, cool down to room temperature, and then transfer the reaction product to a ball mill for ball milling to obtain a 0.5-0.8μm mixture, and finally dry it to obtain the modified composite filler;

[0008] The mass ratio of the dimethyl silicone oil, attapulgite and humic acid is 0.05:1:1-1.1;

[0009] Step 2, place the container containing acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide and stir and react in the water bath environment for 5-10 minutes to obtain a reaction solution; mix the modified composite filler obtained in Step 1 with the reaction solution, and then add N,N'-methylenebisacrylamide and ammonium persulfate, and continue to stir and react in the water bath environment for 60-70 minutes to obtain a primary water-retaining composite organic fertilizer;

[0010] The mass ratio of the acrylic acid, acrylamide and modified composite filler is 2-3:1:10;

[0011] The addition amount of the N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid;

[0012] Step 3, crush the primary water-retaining composite organic fertilizer to a particle size of 5-15μm to obtain a primary water-retaining composite organic fertilizer powder;

[0013] Step 4, place the container containing acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide and stir and react in the water bath environment for 5-10 minutes to obtain a reaction solution; add the primary water-retaining composite organic fertilizer powder, humic acid, mushroom bran, attapulgite and modified attapulgite prepared in Step 3 to the reaction solution, and then add N,N'-methylenebisacrylamide and ammonium persulfate, stir and react in the water bath environment for 60-70 minutes, after the reaction is completed, air-dry it, and finally crush it to a particle size of 1-2.5 cm to obtain the water-retaining composite organic fertilizer;

[0014] The mass ratio of the acrylic acid and acrylamide is 2-3:1;

[0015] The mass ratio of the acrylic acid, the primary water-retaining composite organic fertilizer powder, the humic acid, the mushroom bran, the attapulgite clay, and the modified attapulgite clay is 0.1:0.1:7.5:2:2 to 2.5:7;

[0016] The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of the acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of the acrylic acid;

[0017] The preparation method of the modified attapulgite clay is as follows: Mix dimethyl silicone oil and attapulgite clay with a particle size of 75 - 100 μm, then place them in a reaction kettle at 350 - 360 °C for reaction for 80 - 90 min. After the reaction, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 - 0.8 μm mixture, and finally dry it to obtain the modified composite filler.

[0018] The principle and beneficial effects of the present invention are as follows:

[0019] In the present invention, after mixing dimethyl silicone oil, attapulgite clay, and humic acid for high-temperature reaction, the organic distillation products generated by the humic acid at high temperature are fully miscible with dimethyl silicone oil and infiltrate into the pores of the attapulgite clay and humic acid in the form of organic vapor at high temperature, realizing the local hydrophobic treatment of the attapulgite clay and humic acid, and using the active functional groups such as carboxyl groups and phenolic hydroxyl groups in the humic acid to functionalize and modify the attapulgite clay to obtain the modified composite filler; the modified composite filler is then compounded with the acrylic acid-acrylamide copolymer to form the primary water-retaining composite organic fertilizer. In order to further disperse the modified composite filler and further introduce hydrophobic components into the organic fertilizer, the present application pulverizes the primary water-retaining composite organic fertilizer to the micron level again and re-compounds it with the acrylic acid-acrylamide copolymer for the second time. At the same time of the second compounding, functional components such as humic acid, mushroom bran, attapulgite clay, and modified attapulgite clay are added into the organic fertilizer.

[0020] The present invention utilizes the fact that the humic acid contains abundant active functional groups such as carboxyl groups and phenolic hydroxyl groups, which can form hydrogen bonds with water molecules, thereby increasing the water absorption of the fertilizer; the aromatic ring structure in the humic acid also forms an interpenetrating network with the cellulose of the mushroom bran through π-π stacking, further optimizing the pore distribution and synergistically enhancing the water retention ability, thus achieving a better water retention effect. The mushroom bran has a porous structure, which helps to improve the water holding capacity of the fertilizer; the attapulgite clay has good cation exchange ability and a large specific surface area, and its layered structure can adsorb a large amount of water molecules, having excellent water absorption and water retention characteristics. After the local hydrophobic treatment of the attapulgite clay and humic acid in the organic fertilizer, the adsorption of water by the water circulation channels in the attapulgite clay and humic acid is reduced, the migration ability of water molecules in the attapulgite clay and humic acid is improved, and then the migration ability of water molecules in the organic fertilizer is improved. The water storage efficiency and water capture efficiency of the organic fertilizer are improved, and the capillary porosity of the soil is increased, realizing efficient and rapid water storage.

[0021] After the water-retaining composite organic fertilizer of the present invention is stable in water absorption, it presents a gel state. The hydrophobic treatment improves the migration ability of water molecules in the organic fertilizer, and water channels are formed in the soil around the organic fertilizer due to the migration of a large number of water molecules, thereby increasing the capillary porosity of the soil and enhancing the water-holding capacity of the soil. After the water-retaining composite organic fertilizer of the present invention is applied to the soil, it significantly improves the distribution of aggregates and enhances the soil's anti-erosion and nutrient storage capabilities.

[0022] In the present invention, functional components are introduced while acrylic acid and acrylamide are copolymerized, and micron-level primary water-retaining composite organic fertilizer is also introduced simultaneously. As a result, a complex interpenetrating polymer network structure is formed among acrylic acid, acrylamide, functional components, and micron-level primary water-retaining composite organic fertilizer. The molecular chains penetrate each other inside the organic fertilizer, improving the stability and water-holding capacity of the organic fertilizer. After the organic fertilizer of the present invention is applied to the soil, it combines with soil particles, improves the soil aggregate structure, increases the soil porosity, promotes the formation of aggregate structure, reduces soil compaction, effectively reduces the soil bulk density, improves the soil structure, and enhances the soil fertility.

[0023] The present invention significantly reduces the dosage of acrylic acid-acrylamide copolymer, significantly reduces the cost, and has good practicability and popularity. Brief Description of the Drawings

[0024] Figure 1 Micrograph of the water-retaining composite organic fertilizer prepared in Example 1;

[0025] Figure 2 Curve graph of the soil water-holding rate of the water-retaining composite organic fertilizer. Detailed Embodiments

[0026] The technical solution of the present invention is not limited to the following specific embodiments listed, but also includes any reasonable combination among the specific embodiments.

[0027] Specific Embodiment 1: The preparation method of the water-retaining composite organic fertilizer in this embodiment is carried out according to the following steps:

[0028] Step 1: Prepare a modified composite filler;

[0029] The preparation method of the modified composite filler is as follows: Mix dimethyl silicone oil, attapulgite clay, and humic acid, then place them in a reaction kettle at 350-360 °C for reaction for 80-90 minutes. After the reaction is completed, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5-0.8 μm mixture, and finally dry it to obtain the modified composite filler;

[0030] The mass ratio of dimethyl silicone oil, attapulgite clay, and humic acid is 0.05:1:1-1.1;

[0031] Step 2: Place the container filled with acrylic acid in a water bath environment. Add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%. Then add acrylamide and stir and react in the water bath environment for 5 - 10 min to obtain a reaction solution. Mix the modified composite filler obtained in Step 1 with the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, and continue to stir and react in the water bath environment for 60 - 70 min to obtain a primary water-retaining composite organic fertilizer;

[0032] The mass ratio of the acrylic acid, acrylamide and the modified composite filler is 2 - 3:1:10;

[0033] The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid;

[0034] Step 3: Crush the primary water-retaining composite organic fertilizer to 5 - 15 μm to obtain a primary water-retaining composite organic fertilizer powder;

[0035] Step 4: Place the container filled with acrylic acid in a water bath environment. Add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%. Then add acrylamide and stir and react in the water bath environment for 5 - 10 min to obtain a reaction solution. Add the primary water-retaining composite organic fertilizer powder, humic acid, mushroom bran, attapulgite, and modified attapulgite prepared in Step 3 to the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, stir and react in the water bath environment for 60 - 70 min. After the reaction is completed, air-dry and finally crush to 1 - 2.5 cm to obtain a water-retaining composite organic fertilizer;

[0036] The mass ratio of the acrylic acid and acrylamide is 2 - 3:1;

[0037] The mass ratio of the acrylic acid, the primary water-retaining composite organic fertilizer powder, humic acid, mushroom bran, attapulgite, and modified attapulgite is 0.1:0.1:7.5:2:2 - 2.5:7;

[0038] The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid;

[0039] The preparation method of the modified attapulgite is: Mix dimethyl silicone oil and attapulgite with a particle size of 75 - 100 μm, then place them in a reaction kettle at 350 - 360 °C and react for 80 - 90 min. After the reaction is completed, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 - 0.8 μm mixture, and finally dry it to obtain a modified composite filler.

[0040] This embodiment has the following beneficial effects:

[0041] In this embodiment, dimethyl silicone oil, attapulgite, and humic acid are mixed and subjected to a high-temperature reaction. After that, the organic distillation products generated by humic acid at high temperature are fully miscible with dimethyl silicone oil and infiltrate into the pores of attapulgite and humic acid in the form of organic vapor at high temperature, realizing the local hydrophobic treatment of attapulgite and humic acid. And the active functional groups such as carboxyl groups and phenolic hydroxyl groups in humic acid are used to functionalize and modify attapulgite, obtaining a modified composite filler. The modified composite filler is then compounded with an acrylic acid-acrylamide copolymer to form a primary water-retaining composite organic fertilizer. In order to further disperse the modified composite filler and further introduce hydrophobic components into the organic fertilizer, the present application pulverizes the primary water-retaining composite organic fertilizer to the micron level again and re-compounds it with the acrylic acid-acrylamide copolymer. At the same time of the secondary compounding, functional components such as humic acid, mushroom bran, attapulgite, and modified attapulgite are added into the organic fertilizer.

[0042] In this embodiment, humic acid contains abundant active functional groups such as carboxyl groups and phenolic hydroxyl groups, which can form hydrogen bonds with water molecules, thereby increasing the water absorption of the fertilizer. The aromatic ring structure in humic acid also forms an interpenetrating network with mushroom bran cellulose through π-π stacking, further optimizing the pore distribution and synergistically enhancing the water retention ability, thus achieving a better water retention effect. Mushroom bran has a porous structure that helps to improve the water holding capacity of the fertilizer. Attapulgite has good cation exchange capacity and a large specific surface area, and its layered structure can adsorb a large amount of water molecules, having excellent water absorption and water retention characteristics. After the local hydrophobic treatment of attapulgite and humic acid in the organic fertilizer, the adsorption of water by the water circulation channels in attapulgite and humic acid is reduced, the migration ability of water molecules in attapulgite and humic acid is improved, and then the migration ability of water molecules in the organic fertilizer is improved. The water storage efficiency and water capture efficiency of the organic fertilizer are increased, and the capillary porosity of the soil is increased, realizing efficient and rapid water storage.

[0043] The water-retaining composite organic fertilizer in this embodiment is in a gel state after water absorption is stable. The hydrophobic treatment improves the migration ability of water molecules in the organic fertilizer, and water flow channels are formed in the soil around the organic fertilizer due to the migration of a large number of water molecules, thereby increasing the capillary porosity of the soil and enhancing the water holding capacity of the soil. After the water-retaining composite organic fertilizer in this embodiment is applied to the soil, it significantly improves the distribution of aggregates and enhances the soil's anti-erosion and nutrient storage capabilities.

[0044] In this embodiment, functional components are introduced while acrylic acid and acrylamide are copolymerized, and micron-sized primary water-retaining compound organic fertilizers are introduced simultaneously. This enables the formation of a complex interpenetrating polymer network structure among acrylic acid, acrylamide, functional components, and micron-sized primary water-retaining compound organic fertilizers, with molecular chains interpenetrating each other inside the organic fertilizer, thereby improving the stability and water-retaining capacity of the organic fertilizer. After the organic fertilizer in this embodiment is applied to the soil, it combines with soil particles, improves the soil aggregate structure, increases soil porosity, promotes the formation of aggregate structures, reduces soil compaction, effectively reduces soil bulk density, improves the soil structure, and enhances soil fertility.

[0045] This embodiment significantly reduces the dosage of acrylic acid-acrylamide copolymer, significantly reduces the cost, and has good practicability and popularity.

[0046] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the particle size of the attapulgite clay in Step 1 is 75 - 100 μm.

[0047] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the drying process in Step 1 is: drying at 30°C - 40°C for 1 - 1.5 h.

[0048] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that the mass fraction of the sodium hydroxide solution in Step 2 is 30% - 45%.

[0049] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that the temperature of the water bath environment in Step 2 is 35°C - 40°C.

[0050] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that the mass fraction of the sodium hydroxide solution in Step 4 is 30% - 45%.

[0051] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that the temperature of the water bath environment in Step 4 is 35°C - 40°C.

[0052] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that the particle size of the attapulgite clay in Step 4 is 75 - 100 μm.

[0053] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that the drying process in Step 4 is: drying at 30°C - 40°C for 1 - 1.5 h.

[0054] Embodiment X: The difference between this embodiment and any one of Embodiments 1 to 9 is that the preparation method of the modified attapulgite in Step 4 is as follows: Mix dimethyl silicone oil and attapulgite with a particle size of 75 - 100 μm, then place them in a reaction kettle at 350 °C for reaction for 80 min. After the reaction, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 - 0.8 μm mixture, and finally dry it to obtain the modified composite filler.

[0055] Example 1:

[0056] In order to solve the problem of poor water retention or water storage capacity after the existing organic fertilizer improves the soil, this example proposes a preparation method of a water-retaining composite organic fertilizer.

[0057] Step 1, prepare a modified composite filler;

[0058] The preparation method of the modified composite filler is as follows: Mix dimethyl silicone oil, attapulgite and humic acid, then place them in a reaction kettle at 350 °C for reaction for 85 min. After the reaction, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 - 0.8 μm mixture, and finally dry it to obtain the modified composite filler;

[0059] The mass ratio of the dimethyl silicone oil, attapulgite and humic acid is 0.05:1:1; the particle size of the attapulgite is 75 - 100 μm;

[0060] The drying process is: drying at 30 °C for 1.5 h;

[0061] Step 2, place the container containing acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide, and stir and react in the water bath environment for 8 min to obtain a reaction solution; mix the modified composite filler obtained in Step 1 with the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, and continue to stir and react in the water bath environment for 65 min to obtain a primary water-retaining composite organic fertilizer;

[0062] The mass ratio of the acrylic acid, acrylamide and modified composite filler is 2.5:1:10;

[0063] The mass fraction of the sodium hydroxide solution is 40%;

[0064] The temperature of the water bath environment is 38 °C;

[0065] The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid;

[0066] Step 3: Crush the primary water-retaining compound organic fertilizer to 10 - 15 μm to obtain the primary water-retaining compound organic fertilizer powder;

[0067] Step 4: Place the container filled with acrylic acid in a water bath environment. Add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%. Then add acrylamide and stir and react in the water bath environment for 8 min to obtain a reaction solution. Add the primary water-retaining compound organic fertilizer powder, humic acid, mushroom bran, attapulgite, and modified attapulgite prepared in Step 3 into the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, stir and react in the water bath environment for 60 min. After the reaction ends, air-dry and finally crush to 1 - 2.5 cm to obtain the water-retaining compound organic fertilizer;

[0068] The mass ratio of the acrylic acid to the acrylamide is 3:1;

[0069] The mass fraction of the sodium hydroxide solution is 30%;

[0070] The temperature of the water bath environment is 40 °C;

[0071] The particle size of the attapulgite is 75 - 100 μm;

[0072] The mass ratio of the acrylic acid, the primary water-retaining compound organic fertilizer powder, the humic acid, the mushroom bran, the attapulgite, and the modified attapulgite is 0.1:0.1:7.5:2:2.5:7;

[0073] The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of the acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of the acrylic acid;

[0074] The preparation method of the modified attapulgite is: Mix dimethyl silicone oil and attapulgite with a particle size of 75 - 100 μm, then place them in a reaction kettle at 350 °C and react for 80 min. After the reaction ends, cool down to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 - 0.8 μm mixture, and finally dry to obtain the modified composite filler;

[0075] The drying process is: Dry at 30 °C for 1 h.

[0076] Comparative example:

[0077] The preparation method of the water-retaining composite organic fertilizer in this comparative example is as follows: Place the container filled with acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide, humic acid, mushroom residue and attapulgite. After the reactants become evenly paste-like, add 1.5% of N,N'-methylenebisacrylamide based on the mass of acrylic acid and 2.0% of ammonium persulfate based on the mass of acrylic acid. Stir and react in a water bath environment at 35°C for 65 minutes. Take out the polymer obtained after the reaction, dry it in an oven at 70°C until it reaches a constant weight, and crush it to obtain the water-retaining composite organic fertilizer.

[0078] The mushroom residue used in the present invention is the remaining culture medium after cultivating edible fungi using corn straw as the culture medium and harvesting the edible fungi. The above experiments were all carried out in the experimental fields of Xinglong Township, Wuchang City. The active accumulated temperature is 2700 - 2800°C; the planting variety is corn variety Qi 302, and the application rate of organic fertilizer is 100 kg / 667 m 2 。

[0079] Performance and characterization tests of the water-retaining composite organic fertilizer:

[0080] 1. Determination of water absorption ratio

[0081] Accurately weigh 0.50 g of the water-retaining composite organic fertilizer sample into a beaker, add sufficient distilled water, and let it stand at room temperature until the sample is saturated with water absorption. Then, filter out the unabsorbed water using filter paper, weigh it, and calculate the water absorption ratio Q (g / g); repeat the test 10 times. After each measurement, dry it in an oven at 60°C until it reaches a constant weight and then conduct the next test. Take the average value.

[0082]

[0083] In this formula, M is the total mass (g) of the water-absorbed saturated sample, m1 is the initial mass (g) of the water-retaining composite organic fertilizer, and m2 is the weight (g) of the filter paper.

[0084] The average water absorption ratio of the water-retaining composite organic fertilizer prepared in Example 1 is 152.48 g / g; while the average water absorption ratio of the comparative example is only 75.02 g / g. After repeating the test 10 times, the fluctuation of the water absorption ratio of the water-retaining composite organic fertilizer prepared in Example 1 does not exceed 5%, showing good ability of repeated water absorption, and thus has good water absorption stability.

[0085] 2. Determination of soil water retention capacity: Measure the actual soil water retention rate, bulk density, actual soil water content and capillary porosity two months after sowing.

[0086] ①. Take soil and put it into a beaker, add 100 g of distilled water, and record the total mass as m0; after standing for 12 h, transfer it to a constant temperature oven at 50°C and weigh it every day, recorded as m.

[0087]

[0088] ②. Take soil samples using the core cutter method. Place the core cutter and the soil in the beaker, add distilled water until the soil sample reaches water saturation, and then drain the water from the saturated soil for 8 hours until all the gravitational water is lost. Weigh the soil sample again. The water absorption of the soil sample at this time is the field water holding capacity. Repeat the measurement 5 times and take the average value.

[0089]

[0090] In this formula, D is the field water holding capacity, g·cm -3 ; m3 is the total weight of the core cutter and the soil, g; m4 is the weight of the core cutter, g; V is the volume of the core cutter, cm 3 .

[0091] ③. Dry the water-saturated core cutter and the soil in the core cutter, and measure the capillary porosity of the soil.

[0092]

[0093] In this formula, Pc is the capillary porosity, %; m4 is the weight of the core cutter, g; m5 is the total weight of the core cutter and the soil when the soil sample reaches water saturation, g; m6 is the total weight of the core cutter and the soil after drying.

[0094] The soil bulk density in Example 1 is 0.64 - 0.69 g·cm -3 , and the soil bulk density in Comparative Example 1 is 0.74 - 0.88 g·cm -3 . The field water holding capacity of the soil in Example 1 is 55%, while the field water holding capacity of the soil in Comparative Example 1 is 46%. As Figure 2 shown, the 30-day soil water retention rate of the soil added with the water-retaining compound organic fertilizer prepared in Example 1 reaches 62%, while the 30-day soil water retention rate of the soil added with the organic fertilizer in Comparative Example 1 is only 42%. The capillary porosity of the soil added with the water-retaining compound organic fertilizer prepared in Example 1 reaches 48%, while the capillary porosity of the soil added with the organic fertilizer in Comparative Example 1 is only 40%.

[0095] 3. Determination of soil organic carbon: Measure the actual soil organic carbon content two months after sowing, and use the potassium dichromate-external heating method for determination; the organic carbon content of the soil added with the water-retaining compound organic fertilizer prepared in Example 1 is 32.56 g·kg -1 , while the organic carbon content of the soil added with the organic fertilizer in Comparative Example 1 is only 22.56 g·kg -1 .

[0096] 4. Aggregate determination:

[0097] The wet-sieving method was used to screen the water-stable aggregates, which were divided into four particle sizes: >2 mm (coarse aggregates), 0.25 - 2 mm (fine and large aggregates), 0.053 - 0.25 mm (micro-aggregates), and <0.053 mm (silt and clay). The masses of the four components were weighed respectively, and the mass percentage contents of soil aggregates with different particle sizes were calculated.

[0098] After testing, the content of <0.053 mm aggregates in Example 1 was 2.08% - 7.45%. The content of 0.053 - 0.25 mm aggregates was 6.91% - 10.01%. The content of 0.25 - 2 mm aggregates was 16.63%, and the rest were >2 mm aggregates; while in Comparative Example 1, the content of <0.053 mm aggregates was 10.84% - 14.85%. The content of 0.053 - 0.25 mm aggregates was 12.40% - 15.81%.

[0099] 5. Saturated hydraulic conductivity: The constant head method was adopted. After the soil sample in the ring cutter was fully saturated in distilled water, a stable water head was provided by a Mariotte bottle, and the water head height was maintained at 5 cm. After starting the water supply, wait for the outflow rate to be stable and then start timing. Record the outflow volume Q within a certain period of time, and then derive the formula for the soil saturated hydraulic conductivity Ks according to Darcy's law Q = KIA:

[0100]

[0101] In the formula, Ks is the soil saturated hydraulic conductivity, mm·min -1 ; 10 is the conversion rate from cm to mm; Q is the outflow volume within a certain period of time, ml; L is the height of the ring cutter, cm; H is the sum of the water head height and the height of the ring cutter, cm; A is the cross-sectional area of the ring cutter, cm 2 ; t is the measurement time, min.

[0102] After the water-retaining compound organic fertilizer in Example 1 was applied to the soil, the saturated hydraulic conductivity reached 2.88 - 3.75 mm·min -1 , which could significantly improve the problem of soil compaction. The saturated hydraulic conductivity of the soil added with the organic fertilizer in Comparative Example 1 was 2.45 - 2.57 mm·min -1 .

Claims

1. A preparation method of a water-retaining compound organic fertilizer, characterized in that: The preparation method of the water-retaining compound organic fertilizer is carried out according to the following steps: Step 1: Prepare a modified composite filler; The preparation method of the modified composite filler is as follows: Mix dimethyl silicone oil, attapulgite, and humic acid, then place them in a reaction kettle at 350-360 °C for reaction for 80-90 min. After the reaction, cool down to room temperature, and then transfer the reaction product to a ball mill for ball milling to obtain a 0.5-0.8 μm mixture, and finally dry it to obtain the modified composite filler; The mass ratio of the dimethyl silicone oil, attapulgite, and humic acid is 0.05:1:1-1.1; Step 2: Place the container containing acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide and stir and react in the water bath environment for 5-10 min to obtain a reaction solution; Mix the modified composite filler obtained in Step 1 with the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, and continue to stir and react in the water bath environment for 60-70 min to obtain a primary water-retaining compound organic fertilizer; The mass ratio of the acrylic acid, acrylamide, and modified composite filler is 2-3:1:10; The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid; Step 3: Crush the primary water-retaining compound organic fertilizer to 5-15 μm to obtain a primary water-retaining compound organic fertilizer powder; Step 4: Place the container containing acrylic acid in a water bath environment, add sodium hydroxide solution to acrylic acid until the neutralization degree of acrylic acid reaches 80%; then add acrylamide and stir and react in the water bath environment for 5-10 min to obtain a reaction solution; Add the primary water-retaining compound organic fertilizer powder, humic acid, mushroom bran, attapulgite, and modified attapulgite prepared in Step 3 to the reaction solution, then add N,N'-methylenebisacrylamide and ammonium persulfate, stir and react in the water bath environment for 60-70 min, dry it after the reaction, and finally crush it to 1-2.5 cm to obtain the water-retaining compound organic fertilizer; The mass ratio of the acrylic acid and acrylamide is 2-3:1; The mass ratio of the acrylic acid, primary water-retaining compound organic fertilizer powder, humic acid, mushroom bran, attapulgite, and modified attapulgite is 0.1:0.1:7.5:2:2-2.5:7; The addition amount of N,N'-methylenebisacrylamide is 1.5% of the mass of acrylic acid, and the addition amount of ammonium persulfate is 2% of the mass of acrylic acid; The preparation method of the modified attapulgite is as follows: Mix dimethyl silicone oil and 75-100 μm attapulgite, then place them in a reaction kettle at 350-360 °C for reaction for 80-90 min. After the reaction, cool down to room temperature, and then transfer the reaction product to a ball mill for ball milling to obtain a 0.5-0.8 μm mixture, and finally dry it to obtain the modified composite filler.

2. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The particle size of the attapulgite in Step 1 is 75-100 μm.

3. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The drying process in Step 1 is: Dry at 30 °C - 40 °C for 1-1.5 h.

4. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution described in Step 2 is 30% to 45%.

5. The preparation method of the water-retaining composite organic fertilizer according to claim 1, wherein: The temperature of the water bath environment described in Step 2 is 35°C to 40°C.

6. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution described in Step 4 is 30% to 45%.

7. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The temperature of the water bath environment described in Step 4 is 35°C to 40°C.

8. The preparation method of the water-retaining composite organic fertilizer according to claim 1, wherein: The particle size of the attapulgite described in Step 4 is 75 to 100 μm.

9. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The drying process described in Step 4 is: drying at 30°C to 40°C for 1 to 1.5 h.

10. The preparation method of the water-retaining composite organic fertilizer according to claim 1, characterized in that: The preparation method of the modified attapulgite described in Step 4 is: mixing dimethyl silicone oil and attapulgite with a particle size of 75 to 100 μm, then placing them in a reaction kettle at 350°C for reaction for 80 min. After the reaction, cool to room temperature, then transfer the reaction product to a ball mill for ball milling to obtain a 0.5 to 0.8 μm mixture, and finally dry to obtain the modified composite filler.

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