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

Abstract

The application discloses resin-coated urea slow-release fertilizer, a preparation method and application thereof, and first prepares resin-coated urea slow-release fertilizer, adopts polystyrene, polyethylene, talcum powder and starch mixture to be dispersed and heated in tetrachloroethylene to prepare coating liquid, then sprays the coating liquid on the surface of dried urea after pretreatment, and with evaporation of the solvent, a resin layer is formed on the particle, and the resin-coated urea slow-release fertilizer is obtained. The resin-coated urea can simulate atmospheric nitrogen deposition, and can more truly simulate the nitrogen deposition mode.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer research technology, and more specifically to a resin-coated urea slow-release fertilizer, its preparation method, and its application. Background Technology

[0002] Since the Industrial Revolution, atmospheric nitrogen (N) deposition has more than tripled, causing widespread impacts on ecosystems. The effects of nitrogen deposition threaten ecosystem stability and function, and negatively impact many human societies and ecological services. Numerous studies have explored these impacts through observational experiments. However, the results of observational studies are difficult to interpret due to the presence of confounding variables such as climate, soil, and vegetation.

[0003] To overcome this limitation, numerous nitrogen addition trials have been conducted in various ecosystems around the world. However, most of these trials involve the application of fast-acting nitrogen fertilizer once or several times a year. The nitrogen release in this experimental approach is a nutrient pulse, which cannot well simulate the chronic pattern of real atmospheric nitrogen deposition occurring every moment. The huge difference between pulsed 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, and its rate varies with precipitation. During rainfall, wet deposition is the primary process, where precipitation rapidly washes nitrogen-containing particles from the air to the surface. At this time, the nitrogen deposition rate is high, and most of the dry deposition also migrates into the soil. During dry periods, dry deposition is dominant, with nitrogen-containing particles in the air settling to the surface primarily by gravity. This process takes longer but occurs at a slower rate, leading to reduced nitrogen input during droughts. The combination of these two factors creates a pattern where atmospheric nitrogen deposition occurs constantly, with higher rates during rainfall and lower rates during dry periods. Furthermore, the rate of nitrogen absorption from dry deposition by plants is closely related to rainfall, especially 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, some even up to 12 times. Studies have found that applying nitrogen fertilizer twice a year overestimates species loss and productivity compared to 12 times per year, partly due to higher soil ammonium accumulation and more pronounced acidification. To date, there is a lack of systematic verification on whether different types of nitrogen fertilizers can effectively reproduce the time dynamics of atmospheric nitrogen deposition.

[0005] Coated fertilizers consist of water-soluble granules encased in a semi-permeable or insoluble coating. Particle size and coating thickness both affect the fertilizer release rate. Previous studies have shown that these parameters may be key characteristics of fertilizer granules used to simulate nitrogen deposition. During rainfall, the coating absorbs water, increasing the internal osmotic pressure and accelerating nutrient release. Conversely, under dry conditions, the internal osmotic pressure is low, resulting in a slow nutrient release rate. While this release pattern is similar to natural nitrogen deposition, the optimal coating material, thickness, and particle size for simulating the time 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 an experimental indicator of future nitrogen deposition increases would fill an important methodological gap. Although some ecological experiments have used coated fertilizers to simulate nitrogen deposition, the effectiveness of this method 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, its preparation method and application, which uses resin-coated urea to simulate atmospheric nitrogen deposition, and can more realistically simulate nitrogen deposition patterns.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

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

[0009] Step 1: Preparation of the coating solution

[0010] A mixture of polystyrene, polyethylene, talc, and starch is dispersed evenly in tetrachloroethylene, then heated to 120-140℃ and stirred to form a uniform coating solution.

[0011] Step 2: Preparation of Coated Urea Slow-Release Fertilizer

[0012] Dry the urea granules at 90-100℃, then spray isocyanate evenly on the surface to form a pre-coating. After spraying and letting stand for 1 minute, spray the coating solution prepared in step one evenly onto the surface of the urea granules. As the solvent evaporates, a resin layer is formed on the granules, thus obtaining resin-coated urea slow-release fertilizer.

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

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

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

[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 above.

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

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

[0020] (1) The resin-coated urea slow-release fertilizer is put into a permeable gauze bag with a specification of 40cm*50cm and a pore size of 2.54*2.54mm. Each bag is filled with 4g and is evenly distributed on the ground at a density of 1 bag / m2.

[0021] (2) One bag was randomly selected each week for a total period 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 inter-weekly nitrogen release rate was calculated.

[0022]

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

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

[0025] This invention provides resin-coated urea, which, compared to fast-acting fertilizers and slow-release fertilizers containing urease inhibitors, can be directly applied to the soil surface without the need for watering or deep burial during application. The slow-release fertilizer reduces ammonia volatilization, thus mitigating the greenhouse effect caused by increased nitrogen dioxide; it also reduces nitrate leaching, thus mitigating eutrophication caused by leaching; and further, it ensures a continuous supply of nitrogen to plants.

[0026] This invention uses resin-coated urea to simulate atmospheric nitrogen deposition. Resin-coated urea releases slowly under drought conditions, but accelerates its release under rainfall conditions due to increased osmotic pressure within the membrane. This release pattern closely matches the characteristics of atmospheric nitrogen deposition, which is continuous in time and fluctuates in intensity with rainfall. Compared to fast-acting fertilizers, resin-coated urea avoids experimental side effects such as soil acidification and nutrient loss caused by pulsed fertilization, improving the accuracy of inferring the ecological effects of real nitrogen deposition. Resin-coated urea can more realistically simulate nitrogen deposition patterns, providing a more effective method for experimental research on the impact of future nitrogen input on ecosystem structure and function. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

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

[0029] Figure 2 The annual atmospheric nitrogen (N) deposition rate, nitrogen release rate of resin-coated urea (0.5 mm coating, 4 mm diameter spheres), and precipitation are all included.

[0030] Figure 3 For correlation analysis: (a) N settling rate and N release rate (R 2 =0.80, P<0.001); (b) N sedimentation rate and precipitation (R 2 =0.81, P<0.001) Precipitation unit is mm; (c) N release rate and precipitation (R 2 =0.99, P<0.001). Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are 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) were mixed in tetrachloroethylene at a concentration of 40 g / L to prepare a coating solution. This solution was then heated to 120-140°C and stirred to form a homogeneous coating liquid. Next, urea granules (typically 3-5 mm in diameter) were placed in a spray tower and dried with hot air (90-100°C). A small amount of isocyanate (1% of the urea weight) was then sprayed onto the urea to form a pre-coating. After 1 minute, the prepared coating solution was sprayed onto the fluidized urea granules. As the solvent evaporated, a resin layer formed on the granules, achieving a coating rate of 5-12%. By adjusting the granule size and resin layer thickness, nine designed fertilizers were produced with diameters of 3, 4, and 5 mm and coating thicknesses of 0.3, 0.5, and 0.7 mm, respectively.

[0034] The experiment consisted of 27 plots (1m × 1m), with 3 replicates per plot, to determine the release time of 9 different fertilizers. 10g of fertilizer was evenly spread on the grass surface of each plot. The fertilizer was checked weekly by opening the fertilizer capsules to inspect for urea, and the dates when no urea residue was found were recorded.

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

[0036] Table 1. Effects of resin-coated urea release duration on globule 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 increasing 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 resin-coated urea with a diameter of 4 mm and a coating thickness of 0.5 mm had a release time of nearly 1 year (51.7 weeks) in arid and semi-arid grasslands.

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

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

[0042] The experiment consisted of three plots (8m × 8m), each plot serving as a replicate. Resin-coated urea (4mm diameter, 0.5mm coating thickness) capable of year-round release was packaged into 156 bags (4g per bag, 40cm × 50cm per bag), divided into three groups of 52 bags each. 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 a plot, with each bag placed in a 1m × 1m square. From May 1, 2021 to April 30, 2022, one bag was randomly selected from each plot weekly. The resin-coated urea granules in each bag were dried in an oven at 60℃ for 24 hours and then weighed using a balance with an accuracy of 0.0001g. The nitrogen release rate was calculated using the following formula:

[0043]

[0044] Where Wn represents the amount of urea released in a certain week, in g; Wn+1 represents the amount of urea released in the next week; This indicates the nitrogen content in the urea, and 40×50 represents the surface area of ​​the fertilizer bag, in cm². -2 10 of them -3 and 10 -8 Used for unit conversion. The unit for nitrogen release rate is kgNha. -1 y -1 .

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

[0046] From May 1, 2021 to April 30, 2022, atmospheric nitrogen deposition, including dry and wet deposition, was measured weekly using precipitation sampling. Particulate matter and rainwater were collected in 0.5 m high plastic containers, and the collection was rinsed weekly with pure water. Samples were stored in polyethylene plastic bottles at -20°C until digestion using alkaline potassium persulfate. Total nitrogen was analyzed using a continuous flow analyzer (FUTURA, Alliance Instruments, France).

[0047] 3. Precipitation measurement

[0048] Rainfall was measured by a rainfall monitoring station (Hebei Pingo Technology, China). The station was placed in an open area, away from trees and buildings, to avoid interfering with rainfall collection. Rainfall was quantified weekly.

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

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing resin-coated urea slow-release fertilizer, characterized in that, Includes the following steps: Step 1: Preparation of the coating solution A mixture of polystyrene, polyethylene, talc, and starch is uniformly dispersed in tetrachloroethylene at a weight ratio of polystyrene: polyethylene: talc: starch = 5:8:6:

1. The mixture is then heated to 120-140℃ and stirred to form a uniform coating solution. Step 2: Preparation of Coated Urea Slow-Release Fertilizer Dry the urea granules at 90-100℃, then spray isocyanate evenly on the surface to form a pre-coating. After spraying and letting stand for 1 minute, spray the coating liquid prepared in step one evenly onto the surface of the urea granules. As the solvent evaporates, a resin layer is formed on the granules, thus obtaining resin-coated urea slow-release fertilizer. The urea granules have a diameter of 4 mm and the resin coating thickness is 0.5 mm.

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

3. The method for preparing resin-coated urea slow-release fertilizer according to claim 1, characterized in that, In step two, the amount of isocyanate sprayed is 1% of the urea quality.

4. A resin-coated urea slow-release fertilizer prepared by the method according to any one of claims 1-3.

5. The application of the resin-coated urea slow-release fertilizer according to claim 4 in simulating atmospheric nitrogen deposition time dynamics.

6. The application according to claim 5, characterized in that, Includes the following steps: (1) The resin-coated urea slow-release fertilizer is packed into a permeable gauze bag. The permeable gauze bag has a specification of 40 cm*50 cm and a pore size of 2.54 * 2.54 mm. Each bag is filled with 4 g and is evenly distributed on the ground at a density of 1 bag / m². (2) One bag was randomly selected each week for a total period 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 g. The inter-weekly nitrogen release rate was calculated. N release rate = Where Wn represents the amount of urea released in a certain week, in g; Wn+1 represents the amount of urea released in the next week.

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