Microbial slow-release fertilizer and preparation method thereof

Abstract

The invention relates to a microbial slow-release fertilizer, and discloses a microbial slow-release fertilizer and a preparation method thereof, the microbial slow-release fertilizer comprises 15-35 parts of activated DNRA bacteria immobilized beads, 10-15 parts of ammonium nitrate, 90-130 parts of urea, 5-15 parts of ammonium bicarbonate, 10-15 parts of ammonium sulfate, 10-15 parts of magnesium sulfate, 5-15 parts of borax, and 5-10 parts of activated carbon. According to the prepared microbial slow-release fertilizer, DNRA bacteria are embedded through the immobilized pellets, nitrate can be converted into ammonia nitrogen capable of being utilized by crops and soil microorganisms through the DNRA bacteria in soil, the fertilizer application cost can be reduced, pollution caused by the nitrate is reduced, and the yield of the fertilizer is increased. Meanwhile, the immobilized pellets are beneficial to maintaining relatively high biomass concentration and biological activity, and the nitrate nitrogen conversion stability of the DNRA bacteria in soil is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of microbial slow-release fertilizer, in particular to a kind of microbial slow-release fertilizer and its preparation method. BACKGROUND

[0002] Microbial slow-release fertilizer is the development and innovation on the basis of traditional slow-release fertilizer in recent years, with stronger nutrient intelligent release control ability. Unlike traditional slow-release fertilizer relying on physical or chemical coating to control nutrient release, microbial slow-release fertilizer introduces specific functional microorganisms, and uses their metabolic activity to regulate nitrogen form transformation and supply mode, which can not only realize slow-release nitrogen supply, but also dynamically regulate nitrogen form in soil, reduce invalid loss, and improve crop nitrogen use efficiency, with the advantages of environmental friendliness and ecological efficiency.

[0003] Currently, common microbial slow-release fertilizers, such as products based on yeast and other broad-spectrum microorganisms, mostly stay at the level of biological activity stimulation or general growth promotion, and the strain function lacks specificity, is easily affected by environmental fluctuations, and is difficult to achieve accurate regulation of nitrogen transformation path. At the same time, such products mostly use simple compounding of microbial powder and slow-release substrate, which has problems such as naked bacteria, easy loss of activity, separation of water and fertilizer, asynchronization of nitrogen release and transformation, etc., leading to disconnection between slow-release and microbial action, and unstable fertilization effect. SUMMARY

[0004] To solve the above technical problems, the present application provides a kind of microbial slow-release fertilizer and its preparation method, which successfully realizes the purpose of converting nitrate into ammonia nitrogen available to crops and soil microorganisms by DNRA bacteria, can prolong fertilizer efficiency, reduce fertilizer application cost, and reduce pollution caused by nitrate.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows:

[0006] A kind of microbial slow-release fertilizer, including activated DNRA bacteria immobilized beads 15-35 parts, ammonium nitrate 10-15 parts, urea 90-130 parts, ammonium bicarbonate 5-15 parts, ammonium sulfate 10-15 parts, magnesium sulfate 10-15 parts, borax 5-15 parts, activated carbon 5-10 parts.

[0007] In the above scheme, the DNRA bacteria immobilized beads are formed by embedding DNRA bacteria in a cross-linked polymer product of polyvinyl alcohol, sodium alginate and gelatinized starch as a carrier.

[0008] The activation method of the DNRA bacterium immobilized beads in the scheme is that the DNRA bacterium immobilized beads are placed in activation water, and are activated and cultured at 25-30°C for one week; the composition of the activation water is as follows: sodium nitrate 50 mg / L, ammonium bicarbonate 190 mg / L, potassium dihydrogen phosphate 25 mg / L, magnesium sulfate 200 mg / L, calcium chloride 300 mg / L, glucose 12.2 mg / L, trace element solution 1 mL / L; the composition of the trace element solution is as follows: ethylenediaminetetraacetic acid 20.0 g / L, zinc sulfate 0.43 g / L, copper sulfate 0.25 g / L, cobalt chloride 0.24 g / L, sodium molybdate 0.22 g / L.

[0009] A preparation method of the microbial slow-release fertilizer as described above is as follows, comprising the following steps:

[0010] (1) polyvinyl alcohol and sodium alginate are sequentially added into water and heated and stirred to dissolve and mix uniformly to obtain a mixed solution one;

[0011] (2) soluble starch is added into water, heated and gelatinized, and then cooled to 70-80°C to obtain a mixed solution two;

[0012] (3) water-based polyurethane emulsion and the mixed solution two are sequentially added into the mixed solution one to mix, and the gel solution is obtained after being cooled to room temperature;

[0013] (4) DNRA bacteria are added into the cooled gel solution, and the bacterium gel mixed solution is obtained after being mixed uniformly;

[0014] (5) boric acid and calcium chloride are dissolved in water to prepare a coagulation solution containing boric acid and calcium chloride, the bacterium gel mixed solution is added dropwise into the coagulation solution under stirring to coagulate and form, and is placed to obtain DNRA bacterium immobilized beads;

[0015] (6) the DNRA bacterium immobilized beads are placed in activation water, and are activated and cultured at 25-30°C for one week;

[0016] (7) the activated DNRA bacterium immobilized beads are mixed with ammonium nitrate, urea, ammonium bicarbonate, ammonium sulfate, magnesium sulfate, borax and activated carbon at a certain proportion at room temperature to obtain the microbial slow-release fertilizer.

[0017] In the scheme, in step (1), the mass percentage content of polyvinyl alcohol in the mixed solution one is 8-20%, and the mass percentage content of sodium alginate is 0.5-1.5%.

[0018] In the scheme, in step (1), the polyvinyl alcohol has a polymerization degree of 1600-1800 and an alcoholysis degree of >99%.

[0019] In the scheme, in step (2), the mass-volume ratio of soluble starch to water is 1:(40-60).

[0020] In the above scheme, in step (3), the solid content of the aqueous polyurethane emulsion is 20-40%, and the mass fraction of the aqueous polyurethane in the gel solution is 0.1-1.2%; the volume ratio of the mixed solution II to the mixed solution I is 1:(10-30).

[0021] In the above scheme, in step (4), the mass-volume ratio of the DNRA bacteria to the gel solution is 1:(3-8).

[0022] In the above scheme, in step (5), the mass fraction of boric acid in the coagulation solution is 3-5%, and the mass fraction of calcium chloride is 2-6%.

[0023] Dissimilatory nitrate reduction (DNRA) is the process of converting nitrate nitrogen to ammonium through nitrite, and the reaction process is NO3 - → NO2 - → NH4 + , using nitrate or nitrite as an electron acceptor and organic carbon as an electron donor to reduce nitrate or nitrite to ammonium. DNRA has the potential to greatly reduce N2O emissions, protect NO3 - from leaching in groundwater and surface water, and use NO3 - generated NH4 + to provide nutrients for primary producers and heterotrophic microorganisms in soil, which is of great significance to improve soil quality and crop growth.

[0024] The slow-release fertilizer with DNRA bacteria as the core can construct a microenvironment that promotes efficient conversion of nitrate to ammonium in the field through the synergistic design of specific strains and functional carriers, thereby realizing systematic optimization in terms of nitrogen supply stability, nitrogen utilization rate improvement, and nitrogen environmental loss control, and showing higher specificity, targeting and controllability.

[0025] Through the above technical scheme, the preparation method of the microbial slow-release fertilizer provided by the present application has the following beneficial effects:

[0026] 1. The present application uses immobilized beads to bury the DNRA bacteria-embedded nitrate slow-release fertilizer in the soil, and can convert nitrate to ammonia nitrogen available to crops and soil microorganisms, reducing fertilizer application costs and reducing pollution caused by nitrate.

[0027] 2、The preparation method of the microbial slow-release fertilizer of the present application is based on immobilized beads, which improves the biomass concentration and can maintain high bacterial activity, so that the system can be stably operated for a long time, not only playing a role of immobilizing microbial inoculants, but also maintaining high activity and slow release, solving the problems of small number of microbial inoculants, easy influence of microbial activity in the production and use process, easy loss of strains, and inability to achieve slow release.

[0028] 3、The immobilized beads of the present application use soluble starch with swelling properties as a carrier, so that the DNRA bacteria are attached between the porous soluble starch, avoiding the partial loss of embedded bacteria due to the too large network pores of the immobilized beads, and low utilization rate.

[0029] 4、The immobilized beads of the present application are independently dispersed and not easy to stick together, have high toughness, are more resistant to soil pressure, have long service life, can be repeatedly used, are easy to operate, have low equipment cost, are biodegradable, have obvious price advantage, and have good water absorption and water retention effect while playing a slow release effect, without causing secondary pollution. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows.

[0031] Figure 1 A preparation method of a microbial slow-release fertilizer provided by the present application is shown in the flow chart.

[0032] Figure 2 The growth indexes of corn seedlings of different treatment groups when corn grows for 15 days are as follows: (a) is the plant height; (b) is the fresh weight; (c) is the leaf length; (d) is the leaf width; and (e) is the root length.

[0033] Figure 3 The growth indexes of corn seedlings of different treatment groups when corn grows for 30 days are as follows: (a) is the plant height; (b) is the fresh weight; (c) is the leaf length; (d) is the leaf width; and (e) is the root length. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application.

[0035] The present application provides a preparation method of a microbial slow-release fertilizer, as shown in Figure 1 The specific steps include the following steps:

[0036] Example 1

[0037] (1) 80 g of polyvinyl alcohol (polymerization degree 1600-1800, alcoholysis degree > 99%), 5 g of sodium alginate were sequentially added into 1 L of water and heated and stirred to dissolve and mix uniformly to obtain a mixed solution one;

[0038] (2) Soluble starch was added into water, heated and gelatinized, and then cooled to 70°C to obtain a mixed solution two;

[0039] (3) The aqueous polyurethane emulsion and the mixed solution two were sequentially added into the mixed solution one for mixing, and the gel solution was obtained after being cooled to room temperature;

[0040] (4) DNRA bacteria were added into the cooled gel solution, and the bacterial gel mixed solution was obtained after being mixed uniformly;

[0041] (5) Boric acid and calcium chloride were dissolved in water to prepare a coagulation solution containing boric acid and calcium chloride, the bacterial gel mixed solution was added dropwise into the coagulation solution under stirring to coagulate and form, and then was placed to obtain DNRA bacteria immobilized beads;

[0042] (6) The DNRA bacteria immobilized beads were placed in activated water and activated and cultured at 25°C for one week;

[0043] (7) 15 parts of the activated DNRA bacteria immobilized beads, 10 parts of ammonium nitrate, 90 parts of urea, 5 parts of ammonium bicarbonate, 10 parts of ammonium sulfate, 10 parts of magnesium sulfate, 5 parts of borax and 5 parts of activated carbon were stirred and mixed at room temperature for 20 minutes to obtain a microbial slow-release fertilizer 1.

[0044] Comparative Example 1

[0045] 5 parts of sweet potato, 5 parts of vinasse, 5 parts of edible fungus residue, 5 parts of monosodium glutamate residue and 5 parts of cake meal were respectively crushed and passed through a 60-mesh sieve, and then were mixed uniformly, and then were fermented at 35°C for 12 days, and were stirred once in the morning and once in the evening each day, and the stirring time was 18 minutes each time, and the stirring rate was 50 revolutions per minute to obtain a material one;

[0046] 15 parts of DNRA bacteria powder, 90 parts of urea, 5 parts of ammonium bicarbonate, 10 parts of ammonium nitrate, 10 parts of ammonium sulfate, 10 parts of magnesium sulfate, 5 parts of borax, 5 parts of activated carbon and 5 parts of the material one were put into a mixer, and after being stirred and mixed uniformly, were sent to a grinder through a metering belt, and were ground, and the particle size could pass through an 80-mesh sieve to obtain a material two;

[0047] The material two sent into a granulator was granulated by adding acid and passing ammonia gas to obtain a material three with suitable granule specifications;

[0048] The material three was placed in a drying machine, hot air was passed through to evaporate water, and the water content of the product was reached, and after cooling, screening and coating, the material three was packaged to obtain a microbial slow-release fertilizer 2.

[0049] Comparative Example 2

[0050] Mix 15 parts DNRA bacterial powder, 90 parts urea, 5 parts ammonium bicarbonate, 10 parts ammonium nitrate, 10 parts ammonium sulfate, 10 parts magnesium sulfate, 5 parts borax, and 5 parts activated carbon in a certain proportion at room temperature for 20 minutes to obtain microbial slow-release fertilizer 3.

[0051] Evaluation of the effects of microbial slow-release fertilizer:

[0052] Using maize as the research subject, this study evaluates the effects of slow-release fertilizers prepared using three different methods on crops.

[0053] Corn seeds from the same batch were pre-screened and uniformly treated to reduce the interference of individual differences on the experimental results. Ten corn seeds of similar size were sown in each experimental group, scattered on the soil surface, and covered with 1 cm of soil. Soil moisture was maintained at 60% by adding tap water. On the day of sowing (day 0), the fertilizers of Example 1 and Comparative Examples 1 and 2 of this invention were applied once; the control group received no fertilizer. Fertilization was performed by mixing 4g of slow-release fertilizer evenly with the substrate and filling it into the soil. No topdressing was applied during the experiment. After 15 days of growth, the roots and seedlings were removed from the soil, washed with filter paper, and dried. Next, root length, leaf length, fresh weight, and dry weight were measured, and the average value for each group was calculated as the result for that treatment group. Figure 2 As shown, on the 15th day after corn sowing, the average leaf width of Example 1 was 2.2 cm, an increase of 22.2% compared to the control group (1.8 cm), 15.8% compared to Comparative Example 2 (1.9 cm), and 10.0% compared to Comparative Example 1 (2.0 cm). The average leaf length of Example 1 was 14.0 cm, an increase of 11.1% compared to the control group (12.6 cm), 7.7% compared to Comparative Example 2 (13.0 cm), and 4.5% compared to Comparative Example 1 (13.4 cm). The average plant height of Example 1 was 25.0 cm, compared to 20.0 cm in the control group, 21.5 cm in Comparative Example 2, and 22.8 cm in Comparative Example 1, representing increases of 25.0%, 16.3%, and 9.6%, respectively. The average root length of Example 1 was 11.0 cm, compared to 10.0 cm in the control group, 10.5 cm in Comparative Example 2, and 10.7 cm in Comparative Example 1, representing increases of 10.0%, 4.8%, and 2.8%, respectively. The average fresh weight of Example 1 was 4.8g, which was significantly higher than that of the control group (3.8g), Comparative Example 2 (4.1g) and Comparative Example 1 (4.4g), representing increases of 26.3%, 17.1% and 9.1%, respectively.

[0054] To further investigate the fertilizer's long-lasting effect, the experimental period was extended to 30 days, during which slow-release fertilizer was applied only once on day 1, while maintaining the same soil moisture content (60%). Figure 3As shown, at the 30th day, Example 1 still exhibited significant fertilizer efficiency persistence. The plant height reached 48.0 cm, which was increased by 20.0% compared with the control group (40.0 cm), and increased by 6.7% and 12.9% compared with Comparative Example 1 (45.0 cm) and Comparative Example 2 (42.5 cm), respectively; the fresh weight was 8.1 g, which was increased by 15.0%, 3.2% and 7.3% compared with the control group (7.0 g), Comparative Example 1 (7.8 g) and Comparative Example 2 (7.5 g), respectively. The other indicators such as leaf width, leaf length, root length, etc. were also synchronously increased, which embodied the strong growth promotion and persistent nitrogen conversion capacity.

[0055] In summary, Example 1 performed best in all growth indicators within 30 days, and the control analysis showed that it was not only superior to the blank control group, but also significantly superior to Comparative Example 1 and Comparative Example 2. This indicated that the immobilized DNRA bacteria technology used in the present application could more efficiently convert nitrogen sources and stably promote early plant growth, providing a good foundation for later sustained development. Compared with the traditional commercial resin coated slow-release fertilizer, the immobilized small ball slow-release system used in the present application was composed of polyvinyl alcohol, sodium alginate and gelatinized starch, and the raw materials were cheap and easy to obtain, so it also had certain economy.

[0056] The increase of crop fresh weight represents the formation of organic matter content in the plant growth process, which is an important indicator for evaluating the promotion effect of slow-release fertilizer on crops. The significant increase of fresh weight indicates that the crops applied with slow-release fertilizer can better and more effectively utilize the nitrogen nutrients converted by DNRA bacteria. Generally, fertilizer particles are easily dissolved in water during daily watering and lost with the water flow, resulting in large loss of fertilizer and low utilization rate of fertilizer. Therefore, the nitrogen nutrient content left in the soil is too low to provide sufficient nutrients for the growth of crops. The slow-release fertilizer with immobilized small balls as the carrier can delay the release of nitrogen and at the same time act as a physical barrier to prevent excessive loss of nitrogen. Therefore, the nitrogen nutrients stay in the soil for a longer time, thereby providing long-term and sustained supply of nitrogen nutrients for crops.

[0057] By comparing the three preparation methods, the disadvantages of the granulation method of Comparative Example 1 and the mixing method of Comparative Example 2 are that the bacteria are easily impacted by the external soil environment during the start-up of the DNRA function, and the start-up time and conversion efficiency are unstable, while the immobilized small balls have high water content, which helps to maintain a high biomass concentration and biological activity in the system and enhance the stability of the system operation. Therefore, the immobilized small balls are used to prepare the slow-release fertilizer containing DNRA bacteria in the present application, and by controlling the depth of the nitrate slow-release fertilizer embedding DNRA bacteria in the soil, the amount of fertilizer added, the amount of irrigation water and other conditions, the nitrate slow-release fertilizer embedding DNRA bacteria can convert nitrate into ammonia nitrogen available to crops and soil microorganisms in the soil, thereby reducing the cost of fertilizer application and reducing the pollution caused by nitrate.

[0058] The foregoing description of the disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended 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 microbial slow-release fertilizer, characterized by, The microorganism slow-release fertilizer comprises 15-35 parts of the activated DNRA bacteria immobilized beads, 10-15 parts of ammonium nitrate, 90-130 parts of urea, 5-15 parts of ammonium bicarbonate, 10-15 parts of ammonium sulfate, 10-15 parts of magnesium sulfate, 5-15 parts of borax and 5-10 parts of activated carbon.

2. The microorganism slow-release fertilizer according to claim 1, characterized in that, The DNRA bacteria immobilized beads are formed by embedding DNRA bacteria in a cross-linked polymer product of polyvinyl alcohol, sodium alginate and gelatinized starch.

3. The slow release microbial fertilizer according to claim 1, characterized in that, The activation method of the DNRA bacteria immobilized beads comprises placing the DNRA bacteria immobilized beads in activation water and activating and culturing the DNRA bacteria immobilized beads at 25-30℃ for one week.

4. A process for the preparation of the microbial slow release fertilizer as claimed in any one of claims 1 to 3, wherein the process is carried out as follows, characterized by, The activation water comprises 50mg / L of sodium nitrate, 190mg / L of ammonium bicarbonate, 25mg / L of potassium dihydrogen phosphate, 200mg / L of magnesium sulfate, 300mg / L of calcium chloride and 12.2mg / L of glucose. The microorganism slow-release fertilizer comprises the following steps: (1) adding polyvinyl alcohol and sodium alginate into water in sequence, heating and stirring to dissolve and mix uniformly to obtain a mixed solution one; (2) adding soluble starch into water, heating and gelatinizing, and then cooling to 70-80℃ to obtain a mixed solution two; (3) adding water-based polyurethane emulsion and the mixed solution two into the mixed solution one in sequence, and cooling to room temperature to obtain a gel solution; (4) adding DNRA bacteria into the cooled gel solution, mixing uniformly to obtain a bacteria gel mixed solution; (5) dissolving boric acid and calcium chloride in water to prepare a coagulation solution containing boric acid and calcium chloride, and adding the bacteria gel mixed solution into the coagulation solution under stirring to coagulate and form, and then standing to obtain DNRA bacteria immobilized beads; (6) placing the DNRA bacteria immobilized beads in activation water, and activating and culturing the DNRA bacteria immobilized beads at 25-30℃ for one week; 5. The method for preparing the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, (7) mixing the activated DNRA bacteria immobilized beads with ammonium nitrate, urea, ammonium bicarbonate, ammonium sulfate, magnesium sulfate, borax and activated carbon in proportion at room temperature to obtain the microorganism slow-release fertilizer.

6. The preparation method of the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, In step (1), the mass percentage of polyvinyl alcohol in the mixed solution one is 8-20%, and the mass percentage of sodium alginate is 0.5-1.5%.

7. The preparation method of the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, In step (1), the polymerization degree of the polyvinyl alcohol is 1600-1800, and the alcoholysis degree is >99%.

8. The preparation method of the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, In step (2), the mass-volume ratio of soluble starch to water is 1:(40-60).

9. The preparation method of the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, In step (3), the solid content of the water-based polyurethane emulsion is 20-40%, the mass fraction of water-based polyurethane in the gel solution is 0.1-1.2%, and the volume ratio of the mixed solution two to the mixed solution one is 1:(10-30).

10. The preparation method of the microbial slow-release fertilizer according to claim 4 is as follows, characterized in that, In step (4), the mass-volume ratio of DNRA bacteria to the gel solution is 1:(3-8). In step (5), the mass fraction of boric acid in the coagulation solution is 3-5%, and the mass percentage of calcium chloride is 2-6%.

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