A quick and slow dual-purpose alkali compound fertilizer for red soil dry land and a preparation method thereof

Abstract

The application discloses a kind of red soil dry land quick and slow dual-effect alkali compound fertilizer and preparation method thereof, belong to fertilizer technical field.Function modularization particle design is used, including by weight parts, 35-50 parts of alkaline control particle, 30-45 parts of quick-acting nitrogen phosphorus potassium particle, 15-25 parts of slow-acting nitrogen particle and 3-5 parts of density adjusting component;The alkaline control particle is composed of 20-40 parts of composite alkaline substance, 1-5 parts of hydroxyl modified zeolite and 2-3 parts of gypsum;Among them, the composite alkaline substance is composed of 5-15 parts of limestone powder and 15-25 parts of dolomite powder;The limestone powder is quick-acting alkaline component, and the dolomite powder is slow-acting alkaline component.The beneficial effect is remarkable: first, realize long-acting control red soil dry land acidification, through limestone powder quick-acting neutralization surface acid, dolomite powder long-acting supplement base ion, hydroxyl modified zeolite adsorption buffer, avoid acidification rebound;Second, strengthen exchangeable Al 3+ Passivation, Ca 2+ / Mg 2+ Competitive adsorption sites, hydroxyl zeolite directional adsorption free Al 3+ , Alleviate the harm of aluminum toxicity.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, and more specifically, to a fast-acting and slow-acting alkaline compound fertilizer for red soil and dryland, and its preparation method. Background Technology

[0002] Red soil dryland is an important arable land resource in southern my country, characterized by low pH (typically 4.0-5.5), high activity of toxic metal ions such as aluminum and manganese, low organic matter content, and poor water and fertilizer retention capacity. Under long-term, intensive use, soil acidification has become increasingly serious, leading to decreased nutrient utilization and inhibited crop growth. Traditional improvement methods, such as applying lime alone, can raise soil pH, but the effect is short-lived and cannot provide comprehensive nutrition; while ordinary compound fertilizers are easily fixed in acidic soils, with a utilization rate of less than 40%, and can accelerate the soil acidification process.

[0003] Existing patented alkaline fertilizer technologies have systemic limitations when applied to red soil drylands: On the raw material side, while alkaline residue (CN202211417047) achieves waste utilization, the risks of heavy metal (cadmium, lead) and chloride ion residues remain unresolved, threatening the ecological security of red soil with long-term application. Furthermore, the calcination process (800-950℃, energy consumption of 500-800 kWh per ton) is energy-intensive and does not meet the needs of low-carbon agriculture. At the technical solution level, only neutralizing active acids (such as CN202211417047) with calcium and magnesium oxides is neglected, ignoring the passivation requirements of latent acids (accounting for over 80% of total acidity), leading to pH rebound. Simultaneously, there is a lack of targeted treatment mechanisms for aluminum toxicity (1.5-4.0 cmol / kg). The current methods fail to address the core challenges of red soil improvement. In practical applications, while water-soluble alkaline fertilizers (such as CN202211632857) achieve synergistic acidification through a combination of fast-acting and slow-acting methods, they are prone to leaching in dryland soils (loss rate >30%), contradicting the poor nutrient retention of red soils. Furthermore, hydrogen ion adsorption materials rely on expensive raw materials like tetrabutoxysilane, resulting in complex and costly preparation processes. Regarding long-term effectiveness, acidification effects only last 6-12 months (such as CN202211417047), requiring frequent reapplication. Quicklime (such as CN202310567890) rapidly raises pH but can lead to soil compaction, with a significant pH drop within 2-3 months (a decrease >0.5 units), failing to achieve long-term soil quality improvement. Therefore, developing red soil improvement technologies that combine long-term acidification control, synergistic nutrient supply, and ecological safety is of paramount importance. Summary of the Invention

[0004] The purpose of this invention is to provide a fast-acting and slow-release dual-effect alkaline compound fertilizer for red soil drylands and its preparation method, in order to solve the problems mentioned in the background art. Targeting the unique complex obstacles of "high acidity, high aluminum toxicity, and severe nutrient fixation" in red soil drylands, this invention achieves precise fertilization and soil acidification control through a multi-component synergistic response system, enabling rapid improvement and long-term restoration of red soil drylands. It is suitable for increasing the yield of crops such as soybeans, corn, rapeseed, and peanuts, and can be applied in a single application, saving time and labor.

[0005] A dual-effect alkaline compound fertilizer for red soil and dryland uses a modular granulation design and, by weight, comprises 35-50 parts alkaline control granules, 30-45 parts fast-acting nitrogen, phosphorus and potassium granules, 15-25 parts slow-acting nitrogen granules, and 3-5 parts density regulating components.

[0006] The alkaline control particles are composed of 20-40 parts of composite alkaline substance, 1-5 parts of hydroxyl-modified zeolite, and 2-3 parts of gypsum; wherein the composite alkaline substance is composed of 5-15 parts of limestone powder and 15-25 parts of dolomite powder; the limestone powder is a fast-acting alkaline component, and the dolomite powder is a slow-acting alkaline component.

[0007] Preferably, the limestone powder has a CaO content of ≥85%, and the dolomite powder has a total CaCO3 and MgCO3 content of ≥90%;

[0008] Preferably, the fast-acting nitrogen, phosphorus, and potassium granules are composed of 5-20 parts of ordinary urea, 15-25 parts of monoammonium phosphate, 10-20 parts of potassium chloride, 1-2 parts of citric acid, and 1-5 parts of bentonite.

[0009] Preferably, the urea has an N content ≥ 46%, the monoammonium phosphate has a P2O5 content ≥ 52%, and the potassium chloride has a K2O content ≥ 60%.

[0010] Preferably, the slow-release nitrogen particles are composed of 5-20 parts of ordinary urea particles and 0.3-1 parts of coating material; wherein the coating material is composed of epoxy resin, γ-aminopropyltriethoxysilane and ethanol solvent in a mass ratio of 10:(1-2):(40-50);

[0011] The density-adjusting component comprises 0.5-2.0 parts of lightweight clay and 0.5-2.0 parts of heavy calcium carbonate powder;

[0012] Preferably, the lightweight clay has a particle size of 80-100 mesh and a density of 0.7-0.9 g / cm³; the heavy calcium carbonate powder content is ≥95%, with a particle size of 80-100 mesh and a density of 2.2-2.4 g / cm³. 3 ;

[0013] A method for preparing a fast-acting and slow-release alkaline compound fertilizer for red soil dryland includes the following steps:

[0014] S1. Preparation of three functional particles: preparation of alkaline control particles, fast-acting nitrogen, phosphorus and potassium particles, and slow-acting nitrogen particles.

[0015] S2. Raw Material Preparation: Take the alkaline control granules, fast-acting nitrogen, phosphorus, and potassium granules, and slow-acting nitrogen granules prepared in S1. Add 2%-3% by weight of lightweight clay to the alkaline control granules and mix for 3-5 minutes using a horizontal mixer (20-25 r / min) to ensure the lightweight clay adheres evenly to the surface of the alkaline control granules. Add 1%-2% by weight of heavy calcium carbonate powder to the fast-acting nitrogen, phosphorus, and potassium granules and mix for 3-5 minutes using a horizontal mixer (20-25 r / min) to ensure the heavy calcium carbonate powder adheres evenly to the surface of the fast-acting nitrogen, phosphorus, and potassium granules. Measure the bulk density of the treated alkaline control granules, fast-acting nitrogen, phosphorus, and potassium granules, and slow-acting nitrogen granules using the hydrostatic bottle method, and adjust the density difference between the three to ≤0.1 g / cm³. 3 (To ensure that the particles do not separate due to density differences during subsequent compounding).

[0016] S3. Density homogenization compounding: The above particles are put into a biaxial blade-rubber buffer compounding machine according to the formula ratio. The surface of the blade of the compounding machine is covered with 5mm thick oil-resistant rubber. The speed is set to 20-25r / min, and the mixture is mixed for 8-10 minutes. The particle uniformity variation coefficient is ≤8%.

[0017] S4. Finished Product Packaging: The mixed granules are metered and packaged to obtain the fast-acting and slow-acting alkaline compound fertilizer for red soil and dryland.

[0018] Preferably, the preparation of the basic control particles in S1 includes the following steps:

[0019] Step 1, Raw material pretreatment: Weigh 20-40 parts by weight of the composite alkaline substance (5-15 parts limestone powder and 15-25 parts dolomite powder) and 1-5 parts of hydroxyl-modified zeolite; crush the composite alkaline substance and hydroxyl-modified zeolite to 80-100 mesh respectively, and the residue after sieving is ≤5%.

[0020] Step 2, Micro-domain synergistic granulation: The pretreated composite alkaline material and hydroxyl-modified zeolite are put into a double helix mixer and dry-mixed for 10-15 minutes at a speed of 30-40 r / min to obtain a mixed powder; the mixed powder is fed into a rotary drum granulator, and deionized water is sprayed into the drum through an ultrasonic atomizing nozzle to control the material moisture content to 2%-3%, the drum speed to 15-25 r / min, and 30℃ constant temperature circulating water is circulated through the outer wall of the drum to keep the granulation temperature ≤40℃ and form wet particles with a particle size of 2-4 mm;

[0021] Step 3, Drying and Sieving: The wet granules are dried by cold air penetration at a speed of 0.8-1.0 m / s and a temperature of 25-30℃ until the moisture content of the granules is ≤1.5%. After cooling to room temperature, they are sieved through a 2-4 mm standard sieve. The powder that passes through the sieve is returned to step S2 for regranulation, and the granules that pass through the sieve are the alkaline control granules.

[0022] Preferably, the preparation of the fast-acting nitrogen, phosphorus, and potassium granules in step S1 includes the following steps:

[0023] Step 1, Raw material pretreatment: Weigh 5-20 parts by weight of ordinary urea, 15-25 parts of monoammonium phosphate, 10-20 parts of potassium chloride, 1-2 parts of citric acid and 1-5 parts of bentonite binder; crush the monoammonium phosphate and potassium chloride to 80-90 mesh, crush the ordinary urea to 60-80 mesh, and prepare a 10%-15% aqueous solution of bentonite.

[0024] Step 2, Acid Buffer-Nutrient Protected Granulation: Put ordinary urea, monoammonium phosphate, and potassium chloride powder into a horizontal mixer and dry mix for 10-15 minutes at a speed of 30 r / min. Add citric acid and continue mixing for 5 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder and spray bentonite aqueous solution simultaneously. Control the total moisture content of the material to 5-7%, the extrusion pressure to 3-4 MPa, and the screw speed to 15 r / min to form particles with a particle size of 2-4 mm.

[0025] Step 3, Cooling and Sieving: Cool the granules naturally to room temperature (no secondary drying required), then sieve them through a 2-4mm standard sieve. The powder that passes through the sieve is returned to step S2 for regranulation, and the granules that pass through the sieve are the fast-acting nitrogen, phosphorus and potassium granules.

[0026] Preferably, the preparation of the slow-release nitrogen particles in step S1 includes the following steps:

[0027] Step 1, Core particle pretreatment: Select ordinary urea particles with a particle size of 1.5-2mm, dry them until the moisture content is ≤1%, and use them as coated core particles;

[0028] Step 2, Preparation of acid-resistant coating solution: Mix epoxy resin and γ-aminopropyltriethoxysilane at a mass ratio of 10:1, add ethanol to prepare a coating solution with a concentration of 15%-20%, and stir until completely dissolved;

[0029] Step 3, Acid-adaptive Coating Granulation: The coated core particles are fed into a bottom-spray fluidized bed coating machine. The hot air temperature is set to 43-46℃ and the air velocity is 1.8-2.0m / s, so that the core particles move in a piston flow. The coating liquid is sprayed onto the surface of the core particles through the bottom spray nozzle. The amount of coating liquid sprayed each time is 5%-8% of the core particle mass. After spraying, 20℃ cold air is introduced to solidify for 5 minutes. The spraying-solidification operation is repeated 4 times to form particles with a coating thickness of 5-8μm.

[0030] Step 4, sieving: After cooling to room temperature, sieve through a 2-4mm standard sieve to remove particles with damaged coatings. The particles remaining on the sieve are the slow-release nitrogen particles.

[0031] Compared with the prior art, the advantages of this invention are:

[0032] (1) Breaking through traditional limitations to achieve long-term acidification control: This invention successfully overcomes the bottleneck problems of traditional red soil acidification control technology, such as "short-term effectiveness, easy rebound, and incomplete aluminum toxicity treatment". Through the systematic design of "synergistic effect of compound alkaline substances + hydroxyl-modified zeolite adsorption + particle size separation process protection", it achieves long-term acidification control of red soil by "neutralizing acid-causing ions, passivating toxic ions, replenishing lost bases, and stabilizing the soil microenvironment". The beneficial effects are significant: First, it achieves long-term pH stability of red soil by rapidly neutralizing surface acid with limestone powder, replenishing base ions with dolomite powder, and using hydroxyl-modified zeolite adsorption buffer to avoid acidification rebound; Second, it strengthens the exchangeable Al 3+ Passivation, with Ca 2+ / Mg 2+ Competitive adsorption sites, directional adsorption of free Al by hydroxyl zeolite 3+ This alleviates the harm of aluminum toxicity; thirdly, it reduces the adverse effects of "fertilization-induced acidification," granulation avoids premature acid-base reactions, reduces phosphorus fixation rate, retains alkaline substances for acidification adjustment efficiency, adds citric acid to inhibit urea hydrolysis and reduce H+ oxidative stress. + This invention not only provides an industrially viable and sustainable technical path for the treatment of acidification in red soil drylands, but also creates a stable acid-base environment for crop growth, laying a core foundation for efficient nutrient absorption and improved crop yield and quality. It is of great supporting significance for the sustainable development of agriculture in red soil drylands.

[0033] (2) Precise and long-lasting nutrient supply, suitable for single-application basal fertilization: This invention achieves a combination of precision and long-lasting nutrient supply, highly adaptable to single-application basal fertilization. It adopts a combination of "ordinary urea + coated urea" to achieve rapid and slow synergistic nitrogen release, covering the entire crop growth period, eliminating the need for topdressing and avoiding nutrient gaps or waste caused by traditional multi-application fertilization. Furthermore, citric acid and hydroxyl-modified zeolite inhibit phosphorus fixation, improving fertilizer utilization.

[0034] (3) The physical properties of granules enable integrated planting and fertilization operations, demonstrating significant labor-saving and cost-reducing benefits, and aligning with agricultural development trends: This invention optimizes the physical properties of granules, endowing them with the advantages of "high strength + uniform density + low moisture absorption," providing technical support for integrated planting and fertilization operations in red soil drylands. High strength ensures the integrity of granules during transportation, storage, and fertilization, resulting in uniform and accurate fertilization; uniform density ensures even distribution of fertilizer, avoiding unevenness; low moisture absorption prevents clumping during storage, improving fertilizer quality and lifespan. Based on this, the "one-time basal application" model is adopted, saving labor, time, and agricultural machinery costs, solving the problems of "labor-intensive, costly, and inefficient" traditional fertilization in red soil areas, aligning with the trend of large-scale and simplified agriculture, possessing significant practical and economic value, and contributing to the efficient and sustainable development of red soil dryland agriculture. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation method of a fast-acting and slow-acting alkaline compound fertilizer for red soil dryland according to the present invention. Detailed Implementation

[0036] Example 1:

[0037] A fast-acting and slow-acting alkaline compound fertilizer for inhibiting acidification of red soil dryland was prepared according to the above scheme, wherein:

[0038] It includes 47 parts of alkaline control granules, 45 parts of fast-acting nitrogen, phosphorus and potassium granules, 6 parts of slow-acting nitrogen granules and 2 parts of density adjustment components;

[0039] The alkaline control particles are composed of 11 parts limestone powder, 28 parts dolomite powder, 5 parts hydroxyl-modified zeolite, and 3 parts gypsum.

[0040] The fast-acting nitrogen, phosphorus, and potassium granules are composed of 5 parts ordinary urea, 24 parts monoammonium phosphate, 12 parts potassium chloride, 1.5 parts citric acid, and 2.5 parts bentonite.

[0041] The slow-release nitrogen granules consist of 5.5 parts ordinary urea granules and 0.5 parts coating material;

[0042] The coating material is composed of epoxy resin, γ-aminopropyltriethoxysilane and ethanol solvent in a mass ratio of 10:1:45; the density adjustment component includes 1 part lightweight clay and 1 part heavy calcium carbonate powder.

[0043] Example 2:

[0044] The difference between this embodiment and Embodiment 1 is that:

[0045] It includes 38 parts of alkaline control granules, 51 parts of fast-acting nitrogen, phosphorus and potassium granules, 9 parts of slow-acting nitrogen granules and 2 parts of density adjustment components;

[0046] The alkaline control particles are composed of 10 parts limestone powder, 22 parts dolomite powder, 4 parts hydroxyl-modified zeolite, and 2 parts gypsum.

[0047] The fast-acting nitrogen, phosphorus and potassium granules are composed of 11 parts ordinary urea, 24 parts monoammonium phosphate, 12 parts potassium chloride, 1.5 parts citric acid and 2.5 parts bentonite;

[0048] The density-adjusting components include 0.8 parts lightweight clay and 1.2 parts heavy calcium carbonate powder.

[0049] Example 3:

[0050] The difference between this embodiment and Embodiment 1 is that:

[0051] It includes 29 parts of alkaline control granules, 56 parts of fast-acting nitrogen, phosphorus and potassium granules, 13 parts of slow-acting nitrogen granules and 2 parts of density adjustment components;

[0052] The alkaline control particles are composed of 12 parts limestone powder, 12 parts dolomite powder, 3.5 parts hydroxyl-modified zeolite, and 1.5 parts gypsum.

[0053] The fast-acting nitrogen, phosphorus and potassium granules are composed of 15 parts ordinary urea, 24 parts monoammonium phosphate, 12 parts potassium chloride, 2 parts citric acid and 3 parts bentonite;

[0054] The density-adjusting components include 0.5 parts lightweight clay and 1.5 parts heavy calcium carbonate powder.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 1 is that the alkaline component consists only of limestone powder.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is that the alkaline component consists only of dolomite powder.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 1 is that the nitrogen component is all ordinary urea, without slow-release nitrogen particles.

[0061] Effect Experiment:

[0062] The fast-acting and slow-acting alkaline compound fertilizer for red soil dryland of the present invention has been tested on soybeans and has achieved good application results.

[0063] The experiment was conducted in Rongxiang Village, Quankang Town, Fengcheng City, Yichun City, Jiangxi Province. The soil is a typical acidic red soil dryland. The soybean variety planted was Gan Dou 10, with a plant spacing of 10 cm and a row spacing of 35 cm. The soil type was typical red soil, with the following basic physicochemical properties: pH = 5.10, organic matter content 17.03 g / kg, total nitrogen content 0.91 g / kg, available nitrogen content 98.83 mg / kg, total phosphorus content 0.48 g / kg, available phosphorus content 25.15 mg / kg, total potassium content 16.27 g / kg, and available potassium content 123.23 mg / kg.

[0064] The experiment included seven treatments: farmers' conventional fertilization (30 kg / mu of Sierte (15-15-15) compound fertilizer applied as basal fertilizer before sowing, and 5 kg / mu of urea and 8 kg / mu of potassium chloride applied as top dressing during flowering); Examples 1-3 (50 kg / mu of basal fertilizer applied once before sowing); and Comparative Examples 1-3 (50 kg / mu of basal fertilizer applied once before sowing). Each treatment was replicated three times, resulting in a total of 21 plots, each with an area of ​​18 m². 2 Randomized block design was used. Plant and soil samples were collected at the soybean seedling, flowering, grain-filling, and maturity stages to determine biomass, nitrogen, phosphorus, and potassium nutrient content, soil nitrate, ammonium nitrogen, and pH. Mature samples were used to determine soil acidification characteristics (pH, exchangeable aluminum ions, exchangeable hydrogen ions, soil acid-base buffer capacity, exchangeable calcium, exchangeable magnesium, exchangeable sodium, exchangeable potassium, base saturation, etc.) and routine physicochemical properties (organic matter, total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus, and available potassium). Yield and its components were measured at harvest and combined with indoor seed evaluation, and the actual yield was calculated based on the dried moisture content.

[0065] The effects of fast-acting and slow-acting dual-effect alkaline compound fertilizer on soybean yield and composition

[0066] Compared with conventional fertilization methods, the fertilizer developed in this invention significantly promotes soybean growth and yield. In Example 1, the total biomass increased by 9.0%, pod dry weight by approximately 13.6%, and grain dry weight by 15.1%; in Example 2, the total biomass increased by approximately 3.3%, and grain dry weight by approximately 14.2%, both showing significant improvements (Table 1). Further comparative analysis shows that the overall yield increase of Example 1 is significantly better than that of Examples 2 and 3. This result fully demonstrates that the rational combination of fast-acting and slow-release nutrients in the fertilizer formula, as well as the scientific addition of alkaline components, and the synergistic effect of these two factors, play a key role in optimizing the yield increase. When compared with the comparative example, the yield increases of each example are higher than those of the comparative example. The increases in total biomass, pod dry weight, and grain dry weight of the comparative example are significantly lower than those of the examples.

[0067] Table 1. Effects of fast-acting and slow-release dual-effect alkaline compound fertilizer on soybean biomass at different growth stages.

[0068]

[0069]

[0070]

[0071] Table 2, based on the soybean yield and component analysis, shows that the fast-acting and slow-release dual-effect alkaline compound fertilizer of this invention significantly optimizes the soybean yield composition and final yield. Compared with conventional fertilization, Example 1 showed an increase of 20.92% in the number of effective pods per plant, 17.33% in the number of grains per plant, and 11.88% in the 100-grain weight, resulting in a final yield increase of 16.87%. Examples 2 and 3 also improved yield components such as the number of effective pods per plant and the 100-grain weight, with yield increases of approximately 7.32% and 6.03% respectively compared to conventional fertilization. Furthermore, all examples outperformed the comparative examples in terms of the number of effective pods per plant, the number of grains per plant, the 100-grain weight, and the yield. In summary, the compound fertilizer of this invention, through the innovative mechanism of "compound alkaline inhibition of acidification and synergistic supply of aluminum toxicity and fast-acting and slow-release nutrients," not only makes up for the shortcomings of conventional fertilization in "acidification regulation / single nutrient supply," but also breaks through the limitations of conventional fertilization in "no acidification adaptation and reliance on multiple topdressings." It comprehensively optimizes the formation of effective pods, grain development, and grain filling process of soybeans, and provides technical support for high and stable soybean yields by overcoming the limitations of conventional fertilization.

[0072] Table 2. Effects of fast-acting and slow-release dual-effect alkaline compound fertilizer on soybean yield and composition.

[0073]

[0074] The impact of fast-acting and slow-release dual-effect alkaline compound fertilizer on soil nutrient supply

[0075] The compound fertilizer of this invention relies on "compound alkaline components (limestone powder for rapid acidification + dolomite powder for long-term basal supplementation) to control red soil acidification, synergistic release of fast and slow-acting nitrogen particles to match the nitrogen requirement of soybeans, citric acid chelation to activate phosphorus, and Ca..." 2+ / Mg 2+The synergistic mechanism of "supplementing and reducing potassium leaching" significantly optimized the speciation and supply stability of nitrogen, phosphorus, and potassium in red soil dryland (Table 3). Compared with conventional fertilization and the comparative examples with formula defects (Comparative Examples 1-3), in terms of nitrogen supply, the synergistic release of fast and slow nitrogen avoided the fluctuation defects of "sudden release in the seedling stage and nutrient deficiency in the later stage," improving the stability of available nitrogen supply throughout the entire growth period. In Example 1, the available nitrogen at maturity was increased by approximately 63.4% compared with the fully available nitrogen in Comparative Example 3, ammonia nitrogen was reduced by approximately 78.1% compared with the fully available alkaline components in Comparative Example 1, and nitrate nitrogen was increased by approximately 40.9% compared with Comparative Example 3, achieving a stable nitrogen supply throughout the entire growth period. In terms of phosphorus, the compound alkaline components in the examples effectively reduced the chemical fixation of phosphorus and enhanced activation with citric acid. The available phosphorus at maturity in Example 1 was increased by approximately 166.7% compared with Comparative Example 1, maintaining phosphorus availability for a long time. In terms of potassium supply, the compound alkaline components in the examples supplemented Ca 2+ , Improving soil structure to reduce leaching, while releasing fast and slow-release potassium in synergistic way, Example 1 showed that the available potassium at maturity was increased by about 62.2% compared to Comparative Example 1, which greatly improved the dynamic stability of potassium and the ability to ensure supply in the later stage, laying a solid foundation for high soybean yields.

[0076] Table 3. Effects of fast-acting and slow-release dual-effect alkaline compound fertilizer on soil nutrients.

[0077]

[0078]

[0079] The effect of fast-acting and slow-release dual-effect alkaline compound fertilizer on soil acidification control

[0080] The fast-acting and slow-acting dual-effect alkaline compound fertilizer of this invention (Examples 1-3) can significantly improve the dynamic changes of pH in red soil, showing significant differences compared with conventional fertilization and comparative examples (Table 4). For example, Example 1 achieves rapid pH adjustment during the seedling stage and steady improvement throughout the entire growth period through "fast-acting alkaline fertilizer for rapid acid adjustment + slow-acting alkaline fertilizer for long-term acid stabilization + fast-acting and slow-acting nitrogen controlled release to reduce acidification". Moreover, the pH fluctuations are small at each growth stage, remaining stable in the suitable weakly acidic range of 5.25-5.49. This not only alleviates the "aluminum toxicity" of red soil, but also provides a stable environment for the transformation of soil nutrients (such as nitrogen nitrification and phosphorus activation), demonstrating the advantage of "rapid-acting + slow-acting nitrogen and alkaline components working synergistically to effectively prevent red soil acidification".

[0081] Table 4. Effects of fast-acting and slow-release dual-effect alkaline compound fertilizer on soil pH during soybean growth period.

[0082] deal with Seedling stage Peak bloom Pod formation period Maturity Conventional fertilization (CK) 4.85 4.78 4.70 4.62 Comparative Example 1 5.31 5.22 5.11 5.06 Comparative Example 2 5.09 5.20 5.35 5.31 Comparative Example 3 5.15 5.19 5.29 5.34 Example 1 5.25 5.34 5.46 5.49 Example 2 5.20 5.25 5.22 5.26 Example 3 5.13 5.17 5.20 5.22

[0083] Compared with conventional fertilization, Example 1 showed a significant reduction in acid-causing ions (Table 5), with exchangeable aluminum ions decreasing by 43.46% and exchangeable hydrogen ions decreasing by 53.13%. The acid-base buffering capacity was enhanced, increasing by 8.75%, thus strengthening the soil's resistance to acidification fluctuations. Basic ions were adequately replenished, with exchangeable calcium, magnesium, and potassium increasing by 39.48%, 37.10%, and 37.14%, respectively, which can neutralize acidity and inhibit acidification. Compared with the comparative examples, Example 1 showed more prominent advantages, with its comprehensive effects in reducing acid-causing ions, increasing buffering capacity, and replenishing basic ions far exceeding those of the comparative examples, synergistically improving the acidification characteristics of red soil in multiple dimensions.

[0084] Table 5. Effects of fast-acting and slow-release dual-effect alkaline compound fertilizer on soil acidification characteristics.

[0085]

[0086]

[0087] The above description is only a preferred embodiment of the present invention (previously described using soybean planting as an example). Its core relies on the technical framework of "compound alkaline components controlling red soil acidification and aluminum toxicity + synergistic fertilization of fast and slow-acting nutrients", which has achieved the technical effect of significantly improving the acidification characteristics of red soil and optimizing crop growth and yield formation. However, the present invention is not limited to soybean as a single crop, and can also be adapted to the fertilizer requirements of different crops by adjusting the nitrogen, phosphorus and potassium ratios. It is not limited to a fixed nutrient ratio.

[0088] This technical system can specifically adjust the nitrogen, phosphorus, and potassium ratios according to the nutrient requirements of different crops (corn, peanuts, rapeseed, tobacco, sweet potatoes, etc.) in red soil areas. As long as the core technology (compound alkaline inhibition acidification + synergistic effect of fast-acting and slow-acting nutrients) with the same essence as this invention is adopted, and the nitrogen, phosphorus, and potassium ratios are reasonably adjusted according to the nutrient requirements of different crops, the same red soil acidification inhibition effect and crop yield and quality improvement benefits can be achieved. Regardless of the type of red soil dryland suitable crops such as corn, peanuts, rapeseed, tobacco, and sweet potatoes, they should all be included in the protection scope of this invention. Within the protection scope of this invention, its technical solutions (such as nitrogen, phosphorus, and potassium ratio optimization, micronutrient matching) and implementation methods (such as adjustment of application time and dosage for different crops) can be reasonably modified and changed according to actual planting scenarios and crop needs. These modifications and changes do not depart from the technical essence and protection purpose of this invention.

[0089] The foregoing has shown and described 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 embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fast-acting and slow-release alkaline compound fertilizer for red soil and dryland, characterized in that, It adopts a functional modular granulation design, and by weight, it consists of 35-50 parts of alkaline control granules, 30-45 parts of fast-acting nitrogen, phosphorus and potassium granules, 15-25 parts of slow-acting nitrogen granules and 3-5 parts of density adjustment components. The alkaline control particles are composed of 20-40 parts of composite alkaline substance, 1-5 parts of hydroxyl-modified zeolite, and 2-3 parts of gypsum; wherein the composite alkaline substance is composed of 5-15 parts of limestone powder and 15-25 parts of dolomite powder; the limestone powder is a fast-acting alkaline component, and the dolomite powder is a slow-acting alkaline component. The fast-acting nitrogen, phosphorus and potassium granules are composed of 5-20 parts of ordinary urea, 15-25 parts of monoammonium phosphate, 10-20 parts of potassium chloride, 1-2 parts of citric acid and 1-5 parts of bentonite. The slow-release nitrogen particles are composed of 5-20 parts of ordinary urea particles and 0.3-1 parts of coating material; wherein the coating material is composed of epoxy resin, γ-aminopropyltriethoxysilane and ethanol solvent in a mass ratio of 10:(1-2):(40-50); The density-adjusting component comprises 0.5-2.0 parts of lightweight clay and 0.5-2.0 parts of heavy calcium carbonate powder; The preparation method of the fast-acting and slow-acting alkaline compound fertilizer for red soil dryland includes the following steps: S1. Preparation of three functional particles: preparation of alkaline control particles, fast-acting nitrogen, phosphorus and potassium particles, and slow-acting nitrogen particles. S2. Raw material preparation: Take the alkaline control granules, fast-acting nitrogen, phosphorus, and potassium granules, and slow-acting nitrogen granules prepared in S1. Add 2%-3% by weight of lightweight clay to the alkaline control granules and mix for 3-5 minutes using a horizontal mixer to ensure the lightweight clay adheres evenly to the surface of the alkaline control granules. Add 1%-2% by weight of heavy calcium carbonate powder to the fast-acting nitrogen, phosphorus, and potassium granules and mix for 3-5 minutes using a horizontal mixer to ensure the heavy calcium carbonate powder adheres evenly to the surface of the fast-acting nitrogen, phosphorus, and potassium granules. Measure the bulk density of the treated alkaline control granules, fast-acting nitrogen, phosphorus, and potassium granules, and slow-acting nitrogen granules using the hydrostatic bottle method, and adjust the density difference between the three to ≤0.1 g / cm³. S3. Density homogenization compounding: The above particles are fed into a biaxial paddle-rubber buffer compounding machine according to the formula ratio. The surface of the paddle of the compounding machine is covered with 5mm thick oil-resistant rubber. The speed is set to 20-25r / min, and the mixture is mixed for 8-10 minutes. The particle uniformity variation coefficient is ≤8% when sampled and tested. S4. Finished Product Packaging: The mixed granules are metered and packaged to obtain the fast-acting and slow-acting alkaline compound fertilizer for red soil and dryland.

2. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland as described in claim 1, characterized in that, The limestone powder has a CaO content of ≥85%, and the dolomite powder has a total CaCO3 and MgCO3 content of ≥90%.

3. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland as described in claim 1, characterized in that, The urea has an N content of ≥46%, the monoammonium phosphate has a P2O5 content of ≥52%, and the potassium chloride has a K2O content of ≥60%.

4. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland as described in claim 1, characterized in that, The lightweight clay has a particle size of 80-100 mesh and a density of 0.7-0.9 g / cm³; the heavy calcium carbonate powder content is ≥95%, with a particle size of 80-100 mesh and a density of 2.2-2.4 g / cm³. 3 .

5. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland as described in claim 1, characterized in that, The preparation of the basic control particles in S1 includes the following steps: Step 1, Raw material pretreatment: Weigh 20-40 parts by weight of the composite alkaline substance (5-15 parts limestone powder and 15-25 parts dolomite powder) and 1-5 parts of hydroxyl-modified zeolite; pulverize the composite alkaline substance and hydroxyl-modified zeolite separately to 80-100 mesh, and after sieving, the residue on the sieve is ≤5%; Step 2, Micro-domain synergistic granulation: The pretreated composite alkaline material and hydroxyl-modified zeolite are put into a double helix mixer and dry-mixed for 10-15 minutes at a speed of 30-40 r / min to obtain a mixed powder; the mixed powder is fed into a drum granulator, and deionized water is sprayed into the drum through an ultrasonic atomizing nozzle to control the material moisture content to 2%-3%, the drum speed to 15-25 r / min, and 30℃ constant temperature circulating water is circulated through the outer wall of the drum to keep the granulation temperature ≤40℃ and form wet particles with a particle size of 2-4 mm; Step 3, Drying and Sieving: The wet granules are dried by cold air penetration at a speed of 0.8-1.0 m / s and a temperature of 25-30℃ until the moisture content of the granules is ≤1.5%. After cooling to room temperature, they are sieved through a 2-4 mm standard sieve. The powder that passes through the sieve is returned to step S2 for regranulation, and the granules that pass through the sieve are the alkaline control granules.

6. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland as described in claim 1, characterized in that, The preparation of the fast-acting nitrogen, phosphorus, and potassium granules in S1 includes the following steps: Step 1, Raw material pretreatment: Weigh 5-20 parts by weight of ordinary urea, 15-25 parts of monoammonium phosphate, 10-20 parts of potassium chloride, 1-2 parts of citric acid and 1-5 parts of bentonite binder; crush the monoammonium phosphate and potassium chloride to 80-90 mesh, crush the ordinary urea to 60-80 mesh, and prepare a 10%-15% aqueous solution of bentonite. Step 2, Acid Buffer-Nutrient Protected Granulation: Put ordinary urea, monoammonium phosphate, and potassium chloride powder into a horizontal mixer and dry mix for 10-15 minutes at a speed of 30 r / min. Add citric acid and continue mixing for 5 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder and spray bentonite aqueous solution simultaneously. Control the total moisture content of the material to 5-7%, the extrusion pressure to 3-4 MPa, and the screw speed to 15 r / min to form particles with a particle size of 2-4 mm. Step 3, Cooling and Sieving: Cool the granules naturally to room temperature and sieve them through a 2-4mm standard sieve. The powder that passes through the sieve is returned to step S2 for regranulation, and the granules that pass through the sieve are the fast-acting nitrogen, phosphorus and potassium granules.

7. The fast-acting and slow-release alkaline compound fertilizer for red soil dryland according to claim 1, characterized in that, The preparation of the slow-release nitrogen particles in S1 includes the following steps: Step 1, Core particle pretreatment: Select ordinary urea particles with a particle size of 1.5-2mm, dry them until the moisture content is ≤1%, and use them as coated core particles; Step 2, Preparation of acid-resistant coating solution: Mix epoxy resin and γ-aminopropyltriethoxysilane at a mass ratio of 10:1, add ethanol to prepare a coating solution with a concentration of 15%-20%, and stir until completely dissolved; Step 3, Acid-adaptive Coating Granulation: The coated core particles are fed into a bottom-spray fluidized bed coating machine. The hot air temperature is set to 43-46℃ and the air velocity is 1.8-2.0m / s, so that the core particles move in a piston flow. The coating liquid is sprayed onto the surface of the core particles through the bottom spray nozzle. The amount of coating liquid sprayed each time is 5%-8% of the core particle mass. After spraying, 20℃ cold air is introduced to solidify for 5 minutes. The spraying-solidification operation is repeated 4 times to form particles with a coating thickness of 5-8μm. Step 4, sieving: After cooling to room temperature, sieve through a 2-4mm standard sieve to remove particles with damaged coatings. The particles remaining on the sieve are the slow-release nitrogen particles.

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