NL2030310B1 - Gypsum-coated slow release fertilizer, and preparation method and use thereof - Google Patents

Abstract

A gypsum-coated slow release fertilizer, and a preparation method and use thereof are provided. The slow release fertilizer has the comprehensive effects of saline-alkali soil 5 amelioration, prevention and control of leaching loss of nutrients, soil conservation, promotion of crop absorption, etc.

Description

GYPSUM-COATED SLOW RELEASE FERTILIZER, AND PREPARATION

METHOD AND USE THEREOF

TECHNICAL FIELD

[OI] The present disclosure relates to the technical field of agricultural fertilizers.

BACKGROUND ART

[02] Soil salinization is an important obstruction factor causing land degradation.

The use of conventional types and application methods of fertilizers in saline-alkali farmland may lead to more nitrogen loss through ammonia volatilization, leaching, denitrification and the like and cause potential risk of agricultural non-point source pollution.

SUMMARY

[03] Technical problems to be solved: the present disclosure is directed to existing practical problems of infertile soil in saline-alkali farmland, impact of salt and alkali on nitrogen transportation and transformation and inhibition of crop absorption, and losses through ammonia volatilization, nitrogen leaching and denitrification due to conventional fertilization.

[04] Technical solutions: a gypsum-coated slow release fertilizer is composed of a kernel and a coating layer. In parts by mass, the kernel includes the following components: 35-55 parts of urea, 0.2-0.5 parts of a urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), 1-3 parts of a nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), 0.3-0.5 parts of a nitrification inhibitor 2-chloro-6-trifluoromethylpyridine (CP), 0.1-0.2 parts of stigmasterol, 0.5-1 part of polyglutamic acid, 5-10 parts of monosilicic acid, 15-30 parts of fulvic acid and 1.5-3 parts of chitosan. The coating layer includes the following components: 15-25 parts of gypsum and 4-6 parts of an adhesive.

[05] The present disclosure has the beneficial effects:

[06] (1) acceleration of elimination of soil salinization;

[07] (2) reduction of nutrient loss;

[08] (3) promotion of crop nutrient absorption;

[09] (4) extensive sources of materials;

[10] (5) simple preparation process; and

[11] (6) synergistic interaction.

BRIEF DESCRIPTION OF THE DRAWINGS

[12] FIG. 1 is a chart of net hydrolysis rates of different fertilizers in low salinity soil (salinity: 3.76 g/kg);

[13] FIG. 2 is a chart of net hydrolysis rates of different fertilizers in medium salinity soil (salinity: 5.49 g/kg);

[14] FIG. 3 is a chart of net hydrolysis rates of different fertilizers in high salinity soil (salinity: 7.83 g/kg);

[15] FIG. 4 is a chart of net nitrification rates of different fertilizers in low salinity soil (salinity: 3.76 g/kg);

[16] FIG. 5 is a chart of net nitrification rates of different fertilizers in medium salinity soil (salinity: 5.49 g/kg);

[17] FIG. 6 is a chart of net nitrification rates of different fertilizers in high salinity soil (salinity: 7.83 g/kg);

[18] FIG. 7 shows images of a field nitrogen balance monitoring facility, in which a shows an image of ammonia volatilization monitoring, b shows an image of nitrogen leaching monitoring, and c shows an image of nitrogen deposition collection monitoring;

[19] FIG. 8 is a chart of cumulated ammonia volatilization amounts of different fertilizers in low salinity soil (salinity: 1.73 g/kg);

[20] FIG. 9 is a chart of cumulated ammonia volatilization amounts of different fertilizers in medium salinity soil (salinity: 3.47 g/kg);

[21] FIG. 10 is a chart of cumulated ammonia volatilization amounts of different fertilizers in high salinity soil (salinity: 5.14 g/kg); and

[22] FIG. 11 is a chart of cumulated nitrogen leaching amounts from soil when different fertilizers are applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[23] Example 1:

[24] Heavy saline-alkali cultivated land in the Hetao Plain of Inner Mongolia was selected as an experimental plot. The surface soil (0-20 cm) of the experimental plot had a salinity of 3.3-9.1 g/kg, a pH of 8.37-8.53, an average organic matter content of 845-10.96 g/kg, a total nitrogen content of 0.39-0.64 g/kg, an alkali-hydrolyzable nitrogen content of 29.2-41.8 mg/kg, an available phosphorus content of 9.26-12.45 mg/kg, and a rapidly available potassium content of 164.9-188.1 mg/kg. Location:

Chengni Village, Sandaoqiao Town, Hangjinhou county, Bayan Nur City, Inner

Mongolia. Surface soil (0-20 cm) samples were collected from the saline-alkali cultivated land in May 2017 as soil for an indoor constant temperature cultivation experiment from June 2017 to September 2017. Three salinity gradients were selected for the soil samples for test, and their average salinities were 3.76 g/kg (low), 5.49 g/kg (medium), and 7.83 g/kg (high), respectively. The soil was chloride-sulfate type saline soil, which was clay loam.

[25] The main implementation steps were as follows:

[26] (1) Fertilizer A was conventional urea.

[27] (2) Slow-release fertilizer B was composed of: 45 parts of urea, 2 parts of nitrification inhibitor DMPP, 0.4 parts of nitrification inhibitor CP, 0.1 part of stigmasterol, 0.8 parts of polyglutamic acid, 8 parts of monosilicic acid, 25 parts of fulvic acid, 2 parts of chitosan. The above raw materials were mixed and stirred fully.

After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. The fertilizer B was free of urease inhibitor and had no coating.

[28] (3) Slow release fertilizer C was composed of: 45 parts of urea, 0.5 parts of urease inhibitor NBPT, 0.1 part of stigmasterol, 0.8 parts of polyglutamic acid, 8 parts of monosilicic acid, 25 parts of fulvic acid, and 2 parts of chitosan. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. The fertilizer C was free of nitrification inhibitor and had no coating.

[29] (4) Slow-release fertilizer D was composed of: 45 parts of urea, 0.5 parts of urease inhibitor NBPT, 2 parts of nitrification inhibitor DMPP, 0.4 parts of nitrification inhibitor CP, 8 parts of monosilicic acid, and 25 parts of fulvic acid. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. The fertilizer D was free of stigmasterol, polyglutamic acid, and chitosan, and had no coating.

[30] (5) Slow-release fertilizer E was composed of: 45 parts of urea, 0.5 parts of urease inhibitor NBPT, 2 parts of nitrification inhibitor DMPP, 0.4 parts of nitrification inhibitor CP, 0.1 part of stigmasterol, 0.8 parts of polyglutamic acid, 8 parts of monosilicic acid, 25 parts of fulvic acid, and 2 parts of chitosan. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. The fertilizer E had no gypsum coating. [BI] (6) Slow-release fertilizer F was composed of: 45 parts of urea, 0.5 parts of urease inhibitor NBPT, 2 parts of nitrification inhibitor DMPP, 0.4 parts of nitrification inhibitor CP, 0.1 part of stigmasterol, 0.8 parts of polyglutamic acid, 8 parts of monosilicic acid, 25 parts of fulvic acid, and 2 parts of chitosan. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. A gypsum coating layer was prepared by grinding 20 parts of gypsum and 5 parts of attapulgite powder, sifting through a 200-mesh sieve and mixing fully. The granulated fertilizer was put into a coating machine to be coated with the gypsum-attapulgite powder mixture for 3 times with a coating thickness of 80 microns.

The fertilizer F was the fertilizer of the present disclosure.

[32] (7) Indoor constant temperature cultivation experiment: three salinity gradients was set in the experiment: low salinity (L, 3.76 g/kg), medium salinity (M, 5.49 g/kg) and high salinity (H, 7.83 g/kg). Fertilizers A, B, C, D, E, and F were applied to the 5 soil samples of each salinity gradient, with no use of fertilizer as control check (denoted by CK), and therefore, there were 7 treatments in total. Taking low salinity for example, the treatments were denoted as L-A, L-B, L-C, L-D, L-E, L-F, and L-CK, and 3 repetitions were made for each treatment.

[33] 100 g of air-dried soil was put into a 350 mL cylindrical glass bottle, and based on a nitrogen fertilizer amount of 0.1 g/kg of pure nitrogen, each fertilizer was correspondingly added according to its nitrogen content. Before the start of the experiment, each fertilizer was added to the soil in the form of an aqueous solution, and the moisture content of the soil was adjusted. The top of the bottle mouth was sealed with a preservative film, and the preservative film was evenly pricked to form small holes for aeration. The whole bottle was then placed into a 28° C constant temperature incubator (TIANJIN TAISITE SPX-250BIII) for shading incubation. Due to strong evaporation in this region, to prevent too low soil moisture from affecting the experimental results during the incubation, the water content of each soil sample of each treatment was slightly increased, and the mass moisture content of the soil was 20 adjusted to 30% (equivalent to about 75% of the maximum water-holding capacity of the soil). During the incubation, water was supplemented regularly (every 2-3 days) to keep the water content of each soil sample of each treatment relatively stable. After the water was added to achieve a mass moisture content of 30% for each treatment, each sample was allowed to stand for two hours. After the water and fertilizer were uniform, soil samples were collected to determine the levels of initial ammonium nitrogen, nitrate nitrogen and inorganic nitrogen at each salinity gradient. Soil samples were collected on days 1, 3, 7, 14, 21, 28, and 35 after incubation. Since sampling was destructive sampling, 21 repetitions were made for each treatment according to the number of samples (each sampling was performed on 3 repetitions). The levels of nitrate nitrogen and ammonium nitrogen were measured.

[34] With controls (L-CK, M-CK, H-CK) in which no any fertilizer was applied, the hydrolysis rates of different fertilizers in the low salinity soil, medium salinity soil and high salinity soil were calculated, respectively, with the results shown in FIG. 1,

FIG. 2 and FIG. 3. It could be seen that the gypsum coating layer could greatly delay the contact and hydrolysis time of the fertilizer with the soil and showed a better control effect on the hydrolysis of the fertilizer.

[35] The results of the calculated net nitrification rates of different fertilizers in the low salinity soil, medium salinity soil and high salinity soil were shown in FIG. 4,

FIG. 5 and FIG. 6. The fertilizer F showed the longest time for its net nitrification rate to reach the peak value, followed by the fertilizer E, the fertilizer D and the fertilizer B, and these fertilizers were all added with nitrification inhibitor components. The fertilizer F exhibited the best control effect on the nitrification process.

[36] The results of this example showed that fertilizer F had the best control effect on the nitrogen hydrolysis and nitrification processes, followed by the fertilizer E. It was shown that the components of the fertilizer provided herein were optimal and the gypsum coating could further enhance the slow release effect of the fertilizer. Thus, it was recommended to use the components and the gypsum coating of the fertilizer F as an optimized formula of the slow release fertilizer for saline-alkali land.

[37] Example 2:

[38] Slight saline-alkali land, medium saline-alkali land and heavy saline-alkali land in Binhai, Jiangsu were selected. Typical test sites were selected on 3 types of saline-alkali farmland of different salinity gradients, where the soil of the slight saline-alkali land test site had a salinity of 1.73 g/kg, a pH of 9.04, and an organic matter content of 7.26 g/kg; the soil of the medium saline-alkali land test site had a salinity of 3.47 g/kg , a PH of 8.77, and an organic matter content of 5.75 g/kg; the soil of the heavy saline-alkali land had a salinity of 5.14 g/kg, a pH of 8.42, and an organic matter content of 3.98 g/kg; and the whole soil profiles of the test sites of the three salinity gradients were silt loam, and with an average surface soil bulk density of 1.42 g/em’. Location: Plot No. 4, Tiaobei Zone No. 11, Tiaozini Reclamation Area, Dongtai

City, Jiangsu Province. The duration of the experiment was from June 2018 to October 2018. Hordeum vulgare was grown as the preceding crop in the slight saline-alkali land and the medium saline-alkali land, and after being harvested, the straws were completely crushed and returned to the land. Lolium perenne L. was grown as the preceding crop in the heavy saline-alkali land. Due to high salinity, Lolium perenne L. was not growing well, and the land was basically bare. The test crop was corn, and the variety of the corn was Jinhai No. 5. The main implementation steps were as follows.

[39] (1) Fertilizer I was conventional urea.

[40] (2) Slow-release fertilizer II was composed of: 50 parts of urea, 0.5 parts of urease inhibitor NBPT, 2 parts of nitrification inhibitor DMPP, 0.5 parts of nitrification inhibitor CP, 0.2 parts of stigmasterol, 0.7 parts of polyglutamic acid, 7 parts of monosilicic acid, 22 parts of fulvic acid, and 2 parts of chitosan. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. The fertilizer II had no gypsum coating.

[41] (3) Slow-release fertilizer III was composed of: 50 parts of urea, 0.5 parts of urease inhibitor NBPT, 2 parts of nitrification inhibitor DMPP, 0.5 parts of nitrification inhibitor CP, 0.2 parts of stigmasterol, 0.7 parts of polyglutamic acid, 7 parts of monosilicic acid, 22 parts of fulvic acid, and 2 parts of chitosan. The above raw materials were mixed and stirred fully. After the water content was adjusted to 26%, the mixture was put into a fertilizer granulator for granulation with a grain diameter of 1-2 mm. A gypsum coating layer was prepared by grinding 20 parts of gypsum and 5 parts of attapulgite powder, sifting through a 200-mesh sieve and mixing fully. The granulated fertilizer was put into a coating machine to be coated with the gypsum-attapulgite powder mixture for 3 times with a coating thickness of 80 microns.

The fertilizer III was the fertilizer of the present disclosure.

[42] (4) Field plot monitoring experiment: 3 plots were chosen in the experiment, which had a low salinity (L, 1.73 g/kg), a medium salinity (M, 3.47 g/kg) and a high salinity (M, 5.14 g/kg), respectively. The experiment was conducted on the 3 types of saline-alkali land different in salinity content, and 9 experimental blocks of 24 m* (4m x 6 m) were excavated on each plot. Three treatments were arranged for each salinity gradient, and 3 repetitions were made for each treatment.

[43] An ammonia volatilization and nitrogen leaching monitoring facility was arranged in the test area, and an aeration device was used to capture the ammonia volatilized from the soil. The device was a polyvinyl chloride (PVC) pipe with an inner diameter of 15 cm and a height of 10 cm. Two pieces of sponge with a thickness of 2 cm and a diameter of 16 cm were immersed in a phosphoglycerol solution and then placed into the PVC pipe, with the lower sponge being 5 cm away from the bottom of the pipe and the upper sponge being flush with the top of the pipe (see FIG. 7: a). A nitrogen leaching collection device was buried in the soil profile of each test plot at a depth of 40 cm (see FIG. 7: b). The collection device was mainly composed of a funnel, a liquid collecting tube, a sampling bottle and a buffer bottle. The funnel had an opening diameter of 40 cm and was filled with quartz, with the lower part being connected to the liquid collecting tube by means of a slim tube. The soil leaching liquid was collected in the liquid collecting tube after passing through the funnel. The leaching liquid was collected regularly and the nitrogen content in the leaching liquid and the leaching amount were measured indoors. A nitrogen deposition collection device was set up in the experimental field (see FIG. 7: ©), and the atmospheric nitrogen deposition amount during the growth stage of the corn was regularly collected and measured.

[44] The above three fertilizers were all applied as base fertilizer in an amount of 8 kg of pure nitrogen per mu, and combined with calcium dihydrogen phosphate in an amount of 50 kg/mu. After being applied to the soil, the fertilizers were fully mixed with the surface soil (0-20 cm) for growing corn. Pure nitrogen was applied during the whole growth period of the corn in an amount of 18 kg/mu, and top dressing was added at the booting and filling stages of the corn in an amount of 5 kg of pure nitrogen per mu each time. The conventional urea was top-dressed. For each salinity gradient, the fertilizers I, II and III were applied as base fertilizers. There were 9 treatments in total, namely L-I, L-IT, L-IIL M-I, M-IL M-III, H-I, H-II and H-III, and 3 repetitions were made for each treatment. After the corn was sowed, the ammonia volatilization amounts in the soils of different treatments were measured on days 1, 2, 3,4,5 6,7, 9, 11, 13, 16, 20, 25, and 30. Meanwhile, the percolating liquid was collected twice before the sowing-jointing stage of the corn; the volume of the percolating liquid collected each time and the concentrations of nitrate nitrogen

NO; ™-N, nitrite nitrogen NO»-N and ammonia nitrogen NH4*-N therein were measured, and the nitrogen leaching amount was calculated. After the experiment of the corn season was finished, the apparent nitrogen balances after the application of different types of fertilizers were calculated based on indicators such as initial nitrogen content in soil, nitrogen fertilizer amount, nitrogen uptake amount by corn plants, residual nitrogen amount in soil, nitrogen deposition, ammonia volatilization, and nitrogen leaching.

[45] The variations of cumulated ammonia volatilization amount in soil with different fertilizers over time were shown in FIG. 8, FIG. 9 and FIG. 10. Th fertilizer

III exhibited a better inhibition effect on ammonia volatilization than the fertilizer II, and the fertilizer II was superior to the traditional urea fertilizer.

[46] The cumulated nitrogen leaching amounts in soil in 30 days after treatment with different fertilizers were shown in FIG. 11. Regardless of the slight, medium or heavy saline-alkali land, the fertilizer III showed the lowest nitrogen leaching at the seedling stage of the corn, followed by the fertilizer II, indicating that at the same level of nitrogen application, the application of the fertilizer III was beneficial to reduce the nitrogen leaching loss.

[47] The apparent soil nitrogen balances during the growth stage of the com for different treatments after the application of different types of fertilizers were shown in

Table 1. It was shown that the corn exhibited the highest nitrogen utilization rate for the fertilizer III and the lowest environmental loss, followed by the fertilizer II, and the two fertilizers were significantly superior to the fertilizer I.

[48] Table 1 Apparent Soil Nitrogen Balances During the Growth stage of the Corn after the Application of Different Types of Fertilizers

N

Initial Total Residual Ammonia

Fertilizer Deposition Absorption / ‚ Leaching Other

Typeof Nitrogen Input N Volatilization

Salinity Amount Amount Amount Amount Loss

Fertilizer Amount kg/m) (K Amount bv © Amount Amount « kg/m) (kg/mu. g/mu) y Crop g/mu) (kg/mu (kg/mu) 8 (kg/mu) (kg/mu) (kg/m) © (kg/mu)

Low Fertilizer 5.95 18 0.25 24.20 9.29 5.44 2.62 3.25 3.60 salinity I

Fertilizer 1 4.89 18 0.25 2314 1061 5.19 2.36 269 229

Fertilizer 0 5.37 18 0.25 2362 172 592 2.04 2.28 166

Medium Fertilizer 4.48 18 0.25 022.73 8.11 5.06 3.39 381 2.36 salt 1

Fertilizer 1 4.04 18 0.25 22.29 8.95 4.88 2.98 324 224

Fertilizer 0 4.21 18 0.25 22.46 9.87 5.29 2.51 286 193

High Fertilizer ) 3.59 18 0.25 21.84 4.38 5.64 4.77 4.53 2.52 salt 1

Fertilizer

I 3.23 18 0.25 21.48 5.53 6.15 401 3,78 2.01

Fertilizer 0 3.84 18 0.25 22.09 6.92 6.96 3.43 302 176

[49] This example showed that the main components disclosed herein had better loss reduction and retention improvement effects than conventional fertilizers, and after the fertilizer was coated with the gypsum, the slow release performance of the fertilizer could be further significantly improved. Therefore, the components of the fertilizer HI and the gypsum-coated slow release fertilizer had good effect of reducing fertilizer and increasing effect on saline-alkali land.

Claims (7)

Conclusions l. Slow-release gypsum-coated fertilizer composed of a core and a coating layer, the core comprising in parts by mass the following components: 35 - 55 parts urea, 0.2 - 0.5 parts of a urease inhibitor N-(n- butyl)-thiophosphoric acid triamide (NBPT), 1 — 3 parts of a nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), 0.3 — 0.5 parts of a nitrification inhibitor 2-chloro-6-trifluoromethylpyridine (CP), 0.1 — 0.2 parts of stigmasterol, 0.5 — 1 part of polyglutamic acid, 5 — 10 parts of monosilicic acid, 15 — 30 parts of fulvic acid and 1.5 -3 parts of chitosan; and wherein the coating layer comprises the following components: 15-25 parts of gypsum and 4-6 parts of an adhesive. The delayed release gypsum-coated fertilizer according to claim 1, wherein the urea has a nitrogen (N) content of > 46% by weight and a water content of <3% by weight. A gypsum-coated delayed release fertilizer according to claim 1, wherein the stigmasterol is a phytosterol in a white powder form having a molecular weight of 412.69 and a dry basis content of > 98% by weight. The delayed release gypsum-coated fertilizer according to claim 1, wherein the monosilicic acid is a pale yellow mixed liquid of monosilicic acid and glycolic acid, with a monosilicic acid content of > 60% by weight and a glycolic acid content of > 20% by weight, and wherein the sum of the two is 100%. A gypsum-coated delayed release fertilizer according to claim 1, wherein the fulvic acid is mineral-derived fulvic acid in a powder form having a water solubility of 100%, a dry basis content of >75% by weight and a pH of 5-71s. The delayed release gypsum coated fertilizer according to claim 1, wherein the chitosan is in a form of a white powder with a deacetylation degree of > 75 S12 - wt% and a dry basis content of > 99 wt%. A gypsum-coated delayed release fertilizer according to claim 1, wherein the adhesive is white attapulgite powder with a specific surface area of > 150 m%/g and a water content of < 5% by weight.