Resin coated urea slow-release fertilizer as well as preparation method and application thereof

Abstract

The invention discloses a resin-coated urea slow-release fertilizer and a preparation method and application thereof.The resin-coated urea slow-release fertilizer is prepared firstly, specifically, a mixture of polystyrene, polyethylene, talcum powder and starch is dispersed and heated in tetrachloroethylene to prepare coating liquid, then the surface of dried urea is pretreated and then sprayed with the coating liquid, and the resin-coated urea slow-release fertilizer is obtained; along with evaporation of the solvent, a resin layer is formed on the particles, and the resin coated urea slow-release fertilizer is obtained. The resin-coated urea is adopted to simulate atmospheric nitrogen sedimentation, so that a nitrogen sedimentation mode can be simulated more truly.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural fertilizer research, and more particularly to a resin-coated urea slow-release fertilizer and a preparation method and application thereof. Background Art

[0002] Atmospheric nitrogen (N) deposition has more than tripled since the Industrial Revolution, causing widespread impacts on ecosystems. The effects of N deposition on ecosystems threaten their stability and function and negatively impact numerous human societies and ecological services. Numerous studies have investigated these impacts through observational experiments. However, the interpretation of these results is difficult due to confounding variables such as climate, soils, and vegetation.

[0003] To overcome this limitation, numerous nitrogen addition experiments have been conducted in diverse ecosystems around the world. However, most of these experiments used fast-acting nitrogen fertilizers applied once or a few times per year. This approach to nitrogen release is a pulse of nutrients that does not accurately simulate the chronic pattern of atmospheric nitrogen deposition, which occurs moment by moment. The significant discrepancy between pulse nitrogen addition and chronic nitrogen deposition can lead to erroneous experimental inferences. While these studies have greatly deepened our understanding of the impacts of nitrogen deposition on grassland ecosystems, many knowledge gaps remain, including a lack of research that more accurately simulates the chronic dynamics of nitrogen deposition.

[0004] Nitrogen deposition is a continuous process, the rate of which varies with precipitation. During periods of rainfall, wet deposition primarily occurs, rapidly washing nitrogen particles from the air to the surface. During this period, nitrogen deposition occurs at high rates, and most dry deposition also migrates to the soil. During periods of no rainfall, dry deposition primarily occurs, with nitrogen particles from the air settling to the surface primarily by gravity. This process occurs over a longer period but at a slower rate, leading to reduced nitrogen input during dry periods. This combination of factors results in a pattern in which atmospheric nitrogen deposition occurs constantly, with more during precipitation and less during periods of no precipitation. Furthermore, the rate of plant uptake of nitrogen from dry deposition is closely related to rainfall, particularly in arid and semi-arid regions. Therefore, precipitation is a key factor influencing the temporal dynamics of nitrogen deposition and plant uptake. To simulate nitrogen deposition, most studies apply nitrogen fertilizer once or several times a year, with some applying as many as 12 times. Studies have found that applying nitrogen fertilizer twice a year overestimates species losses and productivity compared to applying it 12 times a year, partly due to greater ammonium accumulation and more pronounced acidification in the soil. To date, there is a lack of systematic verification on whether different types of nitrogen fertilizers can effectively reproduce the temporal dynamic characteristics of atmospheric nitrogen deposition.

[0005] Coated fertilizers consist of water-soluble particles surrounded by a semipermeable or poorly soluble coating. Both particle size and coating thickness influence the fertilizer release rate. Previous studies have suggested that these parameters may be key characteristics of fertilizer particles for simulating nitrogen deposition. During rainfall, the coating absorbs water, increasing the internal osmotic pressure and stimulating a rapid nutrient release rate. Conversely, under dry conditions, the internal osmotic pressure is low, slowing the nutrient release rate. While this release pattern resembles natural nitrogen deposition, the optimal coating material, thickness, and particle size for mimicking the temporal dynamics of nitrogen deposition remain unknown, and the ability of coated nitrogen fertilizers to replicate these dynamics has never been quantified. Demonstrating the effectiveness of coated nitrogen fertilizers as experimental indicators of future increases in nitrogen deposition would fill an important methodological gap. While some ecological experiments have used coated fertilizers to simulate nitrogen deposition, the effectiveness of this approach in replicating annual nitrogen supply patterns through deposition remains unquantified. Summary of the Invention

[0006] In view of this, the present invention provides a resin-coated urea slow-release fertilizer, a preparation method and application thereof, and uses resin-coated urea to simulate atmospheric nitrogen deposition, which can more realistically simulate the nitrogen deposition pattern.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a resin-coated urea slow-release fertilizer comprises the following steps:

[0009] Step 1: Preparation of coating solution

[0010] Disperse the mixture of polystyrene, polyethylene, talc and starch evenly in tetrachloroethylene, then heat to 120-140°C and stir to form a uniform coating solution;

[0011] Step 2: Preparation of coated urea slow-release fertilizer

[0012] The urea granules are dried at 90-100°C, and then isocyanate is evenly sprayed on the surface to form a pre-coating layer. After the spraying is allowed to stand for 1 minute, the coating liquid prepared in step 1 is evenly sprayed onto the surface of the urea granules. As the solvent evaporates, a resin layer is formed on the granules, thereby obtaining a resin-coated urea slow-release fertilizer.

[0013] Preferably, in step 1, the weight ratio of polystyrene: polyethylene: talc: starch is 5:8:6:1.

[0014] Preferably, in step 1, the concentration of the mixture of polystyrene, polyethylene, talc and starch in tetrachloroethylene is 40 g / L.

[0015] Preferably, the amount of isocyanate sprayed in step 2 is 1% of the mass of the urea.

[0016] Preferably, the urea particles have a diameter of 4 mm and a resin coating thickness of 0.5 mm.

[0017] The present invention also provides a resin-coated urea slow-release fertilizer prepared by the method described in the above technical solution.

[0018] The present invention also provides a resin-coated urea slow-release fertilizer prepared by the method described in the above technical solution, or the use of the resin-coated urea slow-release fertilizer in simulating the time dynamics of atmospheric nitrogen deposition.

[0019] Furthermore, the application includes the following steps:

[0020] (1) The resin-coated urea slow-release fertilizer was placed in a permeable gauze bag with a size of 40 cm*50 cm and a pore size of 2.54*2.54 mm. The filling amount of each bag was 4 g and the bags were evenly distributed on the ground at a density of 1 bag / m2;

[0021] (2) One bag was randomly selected each week for a total of one year. The sample was dried at 60°C for 24 hours and then weighed using a balance with an accuracy of 0.0001 grams. The weekly nitrogen release rate was calculated as follows:

[0022]

[0023] Where Wn represents the urea release in a certain week, in g; Wn+1 represents the urea release in the next week.

[0024] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a resin-coated urea slow-release fertilizer and a preparation method and application thereof, which has the following beneficial effects:

[0025] The present invention provides resin-coated urea. Compared to quick-acting fertilizers and urease inhibitor slow-release fertilizers, this resin-coated urea slow-release fertilizer can be directly applied to the soil surface, eliminating the need for watering or deep burial. This slow-release fertilizer can reduce ammonia volatilization, thereby mitigating the greenhouse effect caused by increased nitrogen dioxide; it can also reduce nitrate leaching, thereby alleviating eutrophication caused by leaching; and it can also ensure that plants continuously receive nitrogen.

[0026] The present invention uses resin-coated urea to simulate atmospheric nitrogen deposition. Resin-coated urea releases nitrogen slowly under drought conditions but accelerates under rainfall due to increased osmotic pressure within the membrane. This release pattern closely matches the characteristics of atmospheric nitrogen deposition, which persists over time and fluctuates in intensity with rainfall. Compared to quick-acting fertilizers, resin-coated urea can avoid experimental side effects such as soil acidification and nutrient loss caused by pulsed fertilization, improving the accuracy of inferences about the ecological effects of actual nitrogen deposition. Resin-coated urea can more realistically simulate nitrogen deposition patterns, providing a more effective method for experimentally studying the impact of increased nitrogen input on ecosystem structure and function in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1 The effect of fertilizer size and coating thickness on fertilizer release rate;

[0029] Figure 2 is the atmospheric nitrogen (N) deposition rate, the nitrogen release rate of resin-coated urea (0.5 mm coating, 4 mm diameter sphere), and precipitation in a year;

[0030] Figure 3 Correlation analysis: (a) N deposition rate and N release rate (R 2 =0.80, P<0.001); (b) N deposition rate and precipitation (R 2 =0.81, P<0.001) precipitation in mm; (c) N release rate and precipitation (R 2 =0.99, P<0.001). DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Preparation method of resin-coated urea slow-release fertilizer:

[0033] First, the resin coating components (25% polystyrene, 40% polyethylene, 30% talc and 5% starch by weight) are mixed in tetrachloroethylene at a concentration of 40g / L to prepare a coating solution, which is then heated to 120-140°C and stirred to form a uniform coating solution. Next, urea particles (generally 3-5mm in diameter) are placed in a spray tower and dried with hot air (90-100°C). A small amount of isocyanate (1% of the urea quality) is then sprayed onto the urea to form a pre-coating. After 1 minute, the prepared coating solution is sprayed onto the fluidized urea particles. As the solvent evaporates, a resin layer is formed on the particles, achieving a coating rate of 5-12%. By adjusting the particle size and resin layer thickness, 9 designed fertilizers were produced, namely: diameters of 3, 4, and 5mm, and coating thicknesses of 0.3, 0.5, and 0.7mm, respectively;

[0034] The experiment involved measuring the release time of nine fertilizers across 27 plots (1 m x 1 m), with three replicates per plot. Ten grams of fertilizer was evenly spread across the grass surface in each plot. The fertilizer was inspected weekly by opening the fertilizer capsule to check for urea. The date when no urea residue was found was recorded.

[0035] The experimental results are shown in Table 1 and Figure 1 As shown:

[0036] Table 1 Effect of release duration of resin-coated urea on ball diameter and coating thickness (DF: degrees of freedom; SS: sum of squares; MS: root mean square)

[0037]

[0038]

[0039] The release duration of resin-coated urea increases with the increase of fertilizer particle diameter and resin coating thickness (weeks = 14.72 × diameter + 24.44 × thickness - 21.07, R 2 =0.98, P<0.0001), among which the release time of resin-coated urea with a diameter of 4 mm and a coating thickness of 0.5 mm in arid and semi-arid grasslands was close to 1 year (51.7 weeks).

[0040] Verify whether fertilizer with a diameter of 4 mm and a thickness of 0.5 mm can simulate atmospheric nitrogen deposition

[0041] 1. Determine the nitrogen release rate of fertilizer:

[0042] The experiment set up three plots (8m×8m), each with a replicate. Resin-coated urea (4mm in diameter, 0.5mm in coating thickness) that can be released throughout the year was put into 156 bags (4g per bag, 40cm×50cm in size) and divided into three groups, each with 52 bags. The bags were made of gauze with a pore size of 2.54mm×2.54mm. Each group of bags was placed on the soil surface of the plot, and each bag was placed in a 1m×1m square. From May 1, 2021 to April 30, 2022, one bag was randomly drawn from each plot every week. The resin-coated urea granules in each bag were dried in an oven at 60°C for 24 hours and then weighed on a balance with an accuracy of 0.0001 grams. The formula for calculating the nitrogen release rate is:

[0043]

[0044] Where Wn represents the urea release in a certain week, in g; Wn+1 represents the urea release in the next week; Indicates the nitrogen content in urea, 40×50 indicates the surface area of ​​the fertilizer bag, in cm -2 , of which 10 -3 and 10 -8 Used for unit conversion. The unit of nitrogen release rate is kgNha -1 y -1 .

[0045] 2. Determination of atmospheric nitrogen deposition rate:

[0046] Atmospheric nitrogen deposition (both dry and wet) was measured weekly from May 1, 2021, to April 30, 2022, using precipitation sampling. Particulate matter and rainwater were collected in 0.5-meter-high plastic buckets, which were then cleared weekly with purified water. Samples were stored in polyethylene bottles at −20°C until digested with alkaline potassium persulfate. Total nitrogen was analyzed using a continuous flow analyzer (FUTURA, Alliance Instruments, France).

[0047] 3. Precipitation measurement

[0048] Precipitation was measured by rainfall monitoring stations (Hebei Pingao Technology, China). The stations were placed in open areas away from trees and buildings to avoid interference with precipitation collection. Precipitation was quantified weekly.

[0049] Experimental results: The annual atmospheric nitrogen deposition in the study area is 14.15 kgN ha -1 , ranging from 2.27-46.01kg Nha -1 y -1Nitrogen deposition (57.21%) and precipitation (87.13%) occurred mainly from May to October, especially in July and August. Nitrogen deposition rate reached its peak during rainfall and decreased significantly during no rainfall ( Figure 2 The release pattern of resin-coated urea (4 mm diameter, 0.5 mm coating thickness) was highly consistent with the amount of nitrogen deposition. The release rate was highest during rainfall and lowest during no rainfall. The nitrogen deposition rate increased with the increase in the nitrogen release rate of the fertilizer (R 2 =0.80, P<0.001), nitrogen deposition (R 2 =0.81) and nitrogen release (R 2 =0.99) increased with the increase of precipitation (P<0.001, Figure 3 ).

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0051] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a resin-coated urea slow-release fertilizer, characterized in that: The following steps are involved: Step 1: Preparation of coating solution Disperse the mixture of polystyrene, polyethylene, talc and starch evenly in tetrachloroethylene, then heat to 120-140°C and stir to form a uniform coating solution; Step 2: Preparation of coated urea slow-release fertilizer The urea granules are dried at 90-100°C, and then isocyanate is evenly sprayed on the surface to form a pre-coating layer. After the spraying is allowed to stand for 1 minute, the coating liquid prepared in step 1 is evenly sprayed onto the surface of the urea granules. As the solvent evaporates, a resin layer is formed on the granules, thereby obtaining a resin-coated urea slow-release fertilizer.

2. The method for preparing a resin-coated urea slow-release fertilizer according to claim 1, wherein In step 1, the weight ratio of polystyrene: polyethylene: talcum powder: starch is 5:8:6:

1.

3. The method for preparing a resin-coated urea slow-release fertilizer according to claim 1, wherein: In step 1, the concentration of the mixture of polystyrene, polyethylene, talc and starch in tetrachloroethylene is 40 g / L.

4. The method for preparing a resin-coated urea slow-release fertilizer according to claim 1, wherein The amount of isocyanate sprayed in step 2 is 1% of the mass of the urea.

5. The method for preparing a resin-coated urea slow-release fertilizer according to claim 1, wherein The urea particles have a diameter of 4 mm and a resin coating thickness of 0.5 mm.

6. A resin-coated urea slow-release fertilizer prepared by the method according to any one of claims 1 to 5.

7. Use of the resin-coated urea slow-release fertilizer prepared by the method according to any one of claims 1 to 5 or the resin-coated urea slow-release fertilizer according to claim 6 in simulating the temporal dynamics of atmospheric nitrogen deposition.

8. The use according to claim 7, characterized in that The following steps are involved: (1) The resin-coated urea slow-release fertilizer was placed in a permeable gauze bag with a size of 40 cm*50 cm and a pore size of 2.54*2.54 mm. The filling amount of each bag was 4 g and the bags were evenly distributed on the ground at a density of 1 bag / m2; (2) One bag was randomly selected each week for a total of one year. The sample was dried at 60°C for 24 hours and then weighed using a balance with an accuracy of 0.0001 grams. The weekly nitrogen release rate was calculated as follows: Where Wn represents the urea release in a certain week, in g; Wn+1 represents the urea release in the next week.

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