Macadamia nut slow release fertilizer and preparation method thereof

Abstract

The invention provides a preparation method of a macadamia nut slow-release fertilizer, which comprises the following steps: (1) dissolving chitosan in an acetic acid aqueous solution, then adding a digitaria sanguinalis extract in a stirring state, incubating, and casting to form a film; (2) mixing the pleurotus eryngii residues and the rape straws, and soaking the mixture in acid liquor; then cellulase is added for enzymolysis; calcining at 600 to 650 DEG C to obtain an active component carrier; and (3) uniformly doping the digitaria sanguinalis extract and the mixed bacteria culture into the active component carrier obtained in the step (2) according to the weight ratio of 2: (3-5), and coating with the film obtained in the step (1) to obtain the slow-release fertilizer. The obtained macadamia nut slow-release fertilizer takes biological source materials as raw materials, has a slow-release effect, only needs less fertilization times, also has excellent fertilizer efficiency, and can significantly promote the yield increase of macadamia nuts.

Description

Technical Field

[0001] The present invention belongs to the technical field of agriculture, relates to the technology of slow-release fertilizers, and specifically relates to a slow-release fertilizer for macadamia nuts and a preparation method thereof. Background Art

[0003] At present, one of the important research directions for improving the macadamia nut planting technology is to develop better fertilizers, including new chemical fertilizers and organic fertilizers. For example, Zhang Jinyun et al. studied the effects of different chemical fertilizer formulations on macadamia nut planting in papers such as "The Influence of Formulated Fertilizers on the Yields of Different Varieties of Macadamia Nuts" and "The Application of the Nutrient Balance Method in Formulated Fertilization of Macadamia Nuts"; another example is that Zheng Shufang et al. studied the effects of different organic fertilizers on the yield and kernel rate of macadamia nuts in "The Influence of 4 Commercial Organic Fertilizers on the Yield and Quality of Macadamia Nut 'Guire 1'".

[0004] However, although the application of chemical fertilizers can efficiently increase the yield and nut quality, the fertilizer effect is short, the utilization rate is low, and excessive application is likely to cause environmental pollution; while the application amount of common organic fertilizers is large and the yield-increasing effect is insufficient. As shown in the aforementioned research by Zheng Shufang, the relevant organic fertilizers only have a promoting effect of 4.6% - 21.3% on the yield.

[0005] Therefore, how to develop a slow-release fertilizer that is environmentally friendly, has a high fertilizer effect, requires less fertilization amount and fewer fertilization times, and is used for the planting of macadamia nuts is an important research topic faced by this field. Summary of the Invention

[0006] Aiming at the defects of the prior art, the purpose of the present invention is to solve the defects in the prior art that the application of ordinary chemical fertilizers has a short fertilizer effect, low utilization rate, and it is difficult to obtain the required fertilizer effect by applying general organic fertilizers, thereby providing a slow-release fertilizer for macadamia nuts and a preparation method thereof that use biogenic materials as raw materials, have a slow-release effect, only require fewer fertilization times, and have excellent fertilizer effects.

[0007] The present invention provides the following technical solutions to achieve the above purpose.

[0008] A preparation method of a slow-release fertilizer for macadamia nuts, the preparation method comprising the following steps:

[0009] (1) Dissolve chitosan in an aqueous acetic acid solution, then add the extract of Digitaria sanguinalis under stirring, incubate at 35 - 40 °C for 1 - 2 hours, remove bubbles by standing, and cast into a film; wherein, the weight ratio of chitosan to the extract of Digitaria sanguinalis is 10:1 - 3; the extract of Digitaria sanguinalis is obtained by hydrothermal extraction of Digitaria sanguinalis;

[0010] (2) Mix Pleurotus eryngii residue and rape straw in a weight ratio of 3 - 5:1, place them in an acid solution, soak at 30 - 40 °C for at least 1 hour, then wash with water until neutral; then add cellulase and carry out enzymatic hydrolysis at 30 - 35 °C for at least 0.5 hour, and then wash off the residual enzyme with water; then calcine at 600 - 650 °C to obtain an active ingredient carrier;

[0011] (3) Uniformly incorporate the Digitaria sanguinalis extract and the mixed bacterial culture into the active ingredient carrier obtained in step (2) in a weight ratio of 2:3 - 5, and then coat with the membrane obtained in step (1) to obtain the slow-release fertilizer;

[0012] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2 - 4 and Frankia fgc6 each cultured in a liquid medium to the stationary phase in a volume ratio of 1:1; the preservation number of Bacillus licheniformis strain 1x2 - 4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197.

[0013] Preferably, the volume fraction of acetic acid in the acetic acid aqueous solution is 1%, and the weight - volume ratio of chitosan to acetic acid is 2 g:1 mL.

[0014] Preferably, the Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: Add the whole grass of Digitaria sanguinalis to water in a weight - volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then rotary evaporate to remove the water to obtain a dry powder.

[0015] Preferably, in step (1), the incubation temperature is 40 °C and the incubation time is 1 hour.

[0016] Preferably, the weight ratio of chitosan to the Digitaria sanguinalis extract is 10:2.

[0017] Preferably, the weight ratio of Pleurotus eryngii residue to rape straw is 4:1.

[0018] Preferably, mix Pleurotus eryngii residue and rape straw, place them in an acid solution, soak at 40 °C for 2 hours, then wash with water until neutral; then add cellulase and carry out enzymatic hydrolysis at 35 °C for 0.5 hour.

[0019] Preferably, in step (2), the calcination temperature is 650 °C and the calcination time is 1 hour.

[0020] Preferably, the weight ratio of the Digitaria sanguinalis extract to the mixed bacterial culture is 1:2, and the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow - release fertilizer has a film - wrapped outer layer and particles of the Digitaria sanguinalis extract, the mixed bacterial culture and the active ingredient carrier in the inner layer.

[0021] A slow-release fertilizer for macadamia nuts, which is prepared by the aforementioned preparation method.

[0022] Advantages of the present invention:

[0023] 1. The raw materials of the present invention are biogenic materials, which can effectively utilize the weed Digitaria sanguinalis that harms farmland, and at the same time effectively recycle the agricultural waste mushroom residue and rape straw;

[0024] 2. The present invention creatively uses the extract of Digitaria sanguinalis to prepare a chitosan film, and obtains a good anti-permeation effect, making it have the application value for coating fertilizers to achieve slow release, and avoiding the potential harm to crops and soil caused by using chemical substances to prepare chitosan films;

[0025] 3. The present invention selects to combine the extract of Digitaria sanguinalis and the fermented product of mixed bacteria, achieving a synergistic effect in promoting the yield increase of macadamia nuts;

[0026] 4. The present invention uses Pleurotus eryngii mushroom residue and rape straw as raw materials, and through specific treatment, prepares a carrier that can carry fertilizer active substances, obtains a further slow-release effect, and thus significantly reduces the number of fertilizations and the amount of fertilizer used. Specific embodiments

[0027] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above invention content still fall within the protection scope of the present invention.

[0028] Example 1

[0029] Preparation of slow-release fertilizer for macadamia nuts:

[0030] (1) Dissolve chitosan in an acetic acid aqueous solution with a volume fraction of 1% v / v, and the weight-volume ratio of chitosan to acetic acid is 2 g:1 mL; then add the extract of Digitaria sanguinalis under stirring, incubate at 40 °C for 1 hour, remove bubbles by standing, and uniformly coat on a nylon cloth with a coater, and dry at 50 °C for 24 hours to obtain a film; among them, the weight ratio of chitosan to the extract of Digitaria sanguinalis is 10:2; the extract of Digitaria sanguinalis is prepared by the following hydrothermal extraction method: Add the whole plant of Digitaria sanguinalis to water at a weight-volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then evaporate the water by rotary evaporation to obtain a dry powder;

[0031] (2) Mix the Pleurotus eryngii mushroom residue and rape straw in a weight ratio of 4:1, place them in an acid solution, soak at 40 °C for 2 hours, and then wash with water until neutral; then add cellulase (10,000 U / mL) and carry out enzymatic hydrolysis at 35 °C for 0.5 hours, and then wash off the residual enzyme with water; then calcine at 650 °C for 1 hour to obtain the active ingredient carrier;

[0032] (3) Uniformly incorporate the Digitaria sanguinalis extract and the mixed bacterial culture into the active ingredient carrier obtained in step (2) in a weight ratio of 2:4, and then coat it with the film obtained in step (1) to obtain the slow-release fertilizer; wherein, the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer is a particle with an outer layer wrapped by a film and an inner layer of Digitaria sanguinalis extract, mixed bacterial culture and active ingredient carrier;

[0033] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6 each cultured to the stationary phase with a liquid medium (LB medium) in a volume ratio of 1:1; the preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197. Both of these two bacteria were generously provided by peers, and their original sources were purchased by peers from their respective preservation centers (i.e., the China General Microbiological Culture Collection Center and the China Center for Type Culture Collection).

[0034] Example 2

[0035] Preparation of Macadamia nut slow-release fertilizer:

[0036] (1) Dissolve chitosan in an acetic acid aqueous solution with a volume fraction of 1% v / v, and the weight-volume ratio of chitosan to acetic acid is 2 g:1 mL; then add the Digitaria sanguinalis extract under stirring, incubate at 35 °C for 2 hours, remove the bubbles by standing, and then uniformly coat it on the nylon cloth with a coater and dry at 50 °C for 24 hours to obtain the film; wherein, the weight ratio of chitosan to the Digitaria sanguinalis extract is 10:3; the Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: Add the whole grass of Digitaria sanguinalis to water in a weight-volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then evaporate the water by rotary evaporation to obtain a dry powder;

[0037] (2) Mix the Pleurotus eryngii mushroom residue and rape straw in a weight ratio of 5:1, place them in an acid solution, soak at 30 °C for 3 hours, and then wash with water until neutral; then add cellulase (10,000 U / mL) and carry out enzymatic hydrolysis at 30 °C for 1 hour, and then wash off the residual enzyme with water; then calcine at 600 °C for 90 minutes to obtain the active ingredient carrier;

[0038] (3) Mix the Digitaria sanguinalis extract and the mixed bacterial culture in a weight ratio of 2:5, and uniformly incorporate them into the active ingredient carrier obtained in step (2), and then coat it with the film obtained in step (1) to obtain the slow-release fertilizer; wherein, the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer is a particle with a film-wrapped outer layer and an inner layer of Digitaria sanguinalis extract, mixed bacterial culture and active ingredient carrier;

[0039] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6 each cultured to the plateau phase in a liquid medium (LB medium) in a volume ratio of 1:1; the preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197. Both of these two bacteria were kindly donated by colleagues, and their original sources were purchased by colleagues from their respective preservation centers (i.e., the China General Microbiological Culture Collection Center and the China Center for Type Culture Collection).

[0040] Example 3

[0041] Preparation of macadamia nut slow-release fertilizer:

[0042] (1) Dissolve chitosan in an acetic acid aqueous solution with a volume fraction of 1% v / v, and the weight-to-volume ratio of chitosan to acetic acid is 2 g:1 mL; then add the Digitaria sanguinalis extract under stirring, incubate at 30 °C for 2 hours, remove bubbles by standing, and uniformly coat it on the nylon cloth with a coater, and dry at 50 °C for 24 hours to obtain a film; wherein, the weight ratio of chitosan to the Digitaria sanguinalis extract is 10:1; the Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: Add the whole grass of Digitaria sanguinalis to water in a weight-to-volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then evaporate the water by rotary evaporation to obtain a dry powder;

[0043] (2) Mix Pleurotus eryngii mushroom residue and rape straw in a weight ratio of 3:1, soak them in acid solution at 35 °C for 2 hours, and then wash them with water until neutral; then add cellulase (10000 U / mL) and carry out enzymatic hydrolysis at 32 °C for 75 minutes, and then wash away the residual enzyme; then calcine at 620 °C for 75 minutes to obtain the active ingredient carrier;

[0044] (3) Mix the Digitaria sanguinalis extract and the mixed bacterial culture in a weight ratio of 2:3, and uniformly incorporate them into the active ingredient carrier obtained in step (2), and then coat it with the film obtained in step (1) to obtain the slow-release fertilizer; wherein, the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer is a particle with a film-wrapped outer layer and an inner layer of Digitaria sanguinalis extract, mixed bacterial culture and active ingredient carrier;

[0045] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6, each cultured in a liquid medium (LB medium) until the stationary phase, in a volume ratio of 1:1; the preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197. Both of these two bacteria were kindly provided by peers, and their original sources were purchased by peers from their respective preservation centers (i.e., the China General Microbiological Culture Collection Center and the China Center for Type Culture Collection).

[0046] Comparative Example 1

[0047] When preparing the chitosan film, the following scheme was adopted:

[0048] Chitosan was dissolved in an acetic acid aqueous solution (10% v / v), and the weight-to-volume ratio of chitosan to acetic acid was 2 g:1 mL. It was stirred until completely dissolved, then 0.1 mL of glutaraldehyde was added, and stirring was continued, followed by standing to completely remove the bubbles; it was evenly coated on a nylon cloth with a coater and dried at 50 °C for 24 hours to obtain the chitosan film.

[0049] Comparative Example 2

[0050] Compared with Example 1, the difference is that the mixed bacterial culture was replaced with a single bacterial culture (Frankia fgc6).

[0051] Preparation of macadamia slow-release fertilizer:

[0052] (1) Chitosan was dissolved in an acetic acid aqueous solution with a volume fraction of 1% v / v, and the weight-to-volume ratio of chitosan to acetic acid was 2 g:1 mL; then, during stirring, the Digitaria sanguinalis extract was added, and it was incubated at 40 °C for 1 hour. After standing to remove the bubbles, it was evenly coated on a nylon cloth with a coater and dried at 50 °C for 24 hours to obtain the film; among them, the weight ratio of chitosan to the Digitaria sanguinalis extract was 10:2; the Digitaria sanguinalis extract was prepared by the following hydrothermal extraction method: The whole grass of Digitaria sanguinalis was added to water at a weight-to-volume ratio of 1 g:10 mL, extracted at 80 °C for 4 hours, and then the water was removed by rotary evaporation to obtain a dry powder;

[0053] (2) Pleurotus eryngii mushroom residue and rape straw were mixed in a weight ratio of 4:1, placed in an acid solution and soaked at 40 °C for 2 hours, and then washed with water until neutral; then, cellulase (10000 U / mL) was added and enzymolysis was carried out at 35 °C for 0.5 hours, and then the residual enzyme was washed off with water; after that, it was calcined at 650 °C for 1 hour to obtain the active ingredient carrier;

[0054] (3) Mix the Digitaria sanguinalis extract and the Frankia fgc6 culture in a weight ratio of 2:4, uniformly incorporate them into the active ingredient carrier obtained in step (2), and then coat them with the membrane obtained in step (1) to obtain the slow-release fertilizer; wherein, the total weight of the Digitaria sanguinalis extract and the Frankia fgc6 culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer is a particle with a membrane-wrapped outer layer and an inner layer of Digitaria sanguinalis extract, Frankia fgc6 culture, and active ingredient carrier;

[0055] The Frankia fgc6 culture is obtained by culturing Frankia fgc6 in a liquid medium (LB medium) until the plateau phase; the preservation number of Frankia fgc6 is CCTCC M207197. This bacterium was kindly donated by a peer, and the original source was purchased by the peer from the China Center for Type Culture Collection.

[0056] Comparative Example 3

[0057] Compared with Example 1, the difference is that no Digitaria sanguinalis extract is added in step (3).

[0058] Preparation of macadamia slow-release fertilizer:

[0059] (1) Dissolve chitosan in an aqueous acetic acid solution with a volume fraction of 1% v / v, and the weight-to-volume ratio of chitosan to acetic acid is 2 g:1 mL; then add the Digitaria sanguinalis extract under stirring, incubate at 40 °C for 1 hour, let it stand to remove bubbles, and then uniformly coat it on the nylon cloth with a coater and dry it at 50 °C for 24 hours to obtain a membrane; wherein, the weight ratio of chitosan to the Digitaria sanguinalis extract is 10:2; the Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: Add the whole plant of Digitaria sanguinalis to water at a weight-to-volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then evaporate the water by rotary evaporation to obtain a dry powder;

[0060] (2) Mix Pleurotus eryngii mushroom residue and rape straw in a weight ratio of 4:1, soak them in acid solution at 40 °C for 2 hours, and then wash them with water until neutral; then add cellulase (10000 U / mL) and carry out enzymatic hydrolysis at 35 °C for 0.5 hours, and then wash away the residual enzyme; then calcine at 650 °C for 1 hour to obtain an active ingredient carrier;

[0061] (3) Uniformly incorporate the mixed bacteria culture into the active ingredient carrier obtained in step (2), and then coat it with the membrane obtained in step (1) to obtain the slow-release fertilizer; wherein, the total weight of the mixed bacteria culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer is a particle with a membrane-wrapped outer layer and an inner layer of mixed bacteria culture and active ingredient carrier;

[0062] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6, each cultured to the plateau phase in a liquid medium (LB medium), in a volume ratio of 1:1. The preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197. Both of these two bacteria were kindly provided by peers, and their original sources were purchased by peers from their respective preservation centers (i.e., the China General Microbiological Culture Collection Center and the China Center for Type Culture Collection).

[0063] Comparative Example 4

[0064] Compared with Example 1, the difference lies in that rapeseed straw is not added in step (2).

[0065] Preparation of macadamia slow-release fertilizer:

[0066] (1) Chitosan is dissolved in an acetic acid aqueous solution with a volume fraction of 1% v / v, and the weight-volume ratio of chitosan to acetic acid is 2 g:1 mL. Then, during stirring, Digitaria sanguinalis extract is added, incubated at 40 °C for 1 hour, allowed to stand to remove air bubbles, and then evenly coated on a nylon cloth with a spreader and dried at 50 °C for 24 hours to obtain a film. Among them, the weight ratio of chitosan to Digitaria sanguinalis extract is 10:2. The Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: The whole grass of Digitaria sanguinalis is added to water at a weight-volume ratio of 1 g:10 mL, extracted at 80 °C for 4 hours, and then the water is removed by rotary evaporation to obtain a dry powder;

[0067] (2) Pleurotus eryngii mushroom residue is immersed in acid solution at 40 °C for 2 hours, and then washed with water until neutral. Then, cellulase (10000 U / mL) is added and enzymolyzed at 35 °C for 0.5 hours, and then the residual enzyme is washed off with water. After that, it is calcined at 650 °C for 1 hour to obtain an active ingredient carrier;

[0068] (3) The Digitaria sanguinalis extract and the mixed bacterial culture are evenly incorporated into the active ingredient carrier obtained in step (2) according to a weight ratio of 2:4, and then coated with the film obtained in step (1) to obtain the slow-release fertilizer. Among them, the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier. After coating, the obtained slow-release fertilizer has a film wrapped on the outer layer and particles of Digitaria sanguinalis extract, mixed bacterial culture, and active ingredient carrier on the inner layer;

[0069] The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6, each cultured in a liquid medium (LB medium) until the stationary phase, in a volume ratio of 1:1. The preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197. Both of these two bacteria were generously provided by peers, and their original sources were purchased by peers from their respective preservation centers (i.e., the China General Microbiological Culture Collection Center and the China Center for Type Culture Collection).

[0070] Experimental Example 1

[0071] The membranes obtained in step (1) of Examples 1 to 3 and the membrane obtained in Comparative Example 1 were used for permeability testing, with urea as the experimental permeate. During the test, the preparation of the color reagent, the preparation of the urea standard solution, and the drawing of the standard curve were referred to GB / T 23348-2009. The test device was improved based on the existing device. Specifically, holes were drilled in the barrel walls of two glass graduated cylinders, and the two holes were connected by a glass catheter. A flange was set in the glass catheter, and the aforementioned membrane was loaded on the flange. 250 mL of a urea aqueous solution with a concentration of 100 g / L was added to one graduated cylinder A, and the same volume of distilled water was loaded into another graduated cylinder B. The liquid in graduated cylinder B was taken every other day, and the color reaction of urea with the color reagent was measured with an ultraviolet spectrophotometer at a wavelength of 430 nm to calculate the urea permeation amount. It was measured for 7 days in total, and the cumulative urea permeability rate for 7 days was calculated.

[0072] Table 1

[0073]

[0074]

[0075] As shown in Table 1, the chitosan membrane obtained in the present invention has low permeability, can prevent urea release, and can achieve a slow-release effect. Compared with the method of cross-linking with glutaraldehyde, the extracts of Digitaria sanguinalis used in Examples 1 to 3 of the present invention also have a cross-linking effect. Although the dosage of the extracts of Digitaria sanguinalis is relatively large, as shown in other experimental examples of the present invention, the presence of the extracts of Digitaria sanguinalis is also helpful for the planting effect of Macadamia integrifolia. Therefore, the use of the extracts of Digitaria sanguinalis in the present invention not only realizes the preparation of the slow-release membrane, but also can be used as an active ingredient of the fertilizer.

[0076] Experimental Example 2

[0077] For 8-year-old Macadamia integrifolia trees, the slow-release fertilizers obtained in Examples 1 to 3 and Comparative Examples 2 to 4 were used for fertilization. The fertilization time was in May and October, and the fertilization amount was 15 kg / tree. The yield (weight with shell) data was collected when fruiting occurred every other year. Using the application of decomposed chicken manure as the control group, the fertilization time and dosage were the same as before. The results are shown in Table 2.

[0078] Table 2

[0079]

[0080] As shown in Table 2, the slow-release fertilizers obtained in Examples 1-3 of the present invention are significantly superior to Comparative Examples 2-4 and the control group in terms of promoting production. Since Comparative Example 2 and Comparative Example 3 lack a kind of bacterial culture and Digitaria sanguinalis extract respectively, it can be seen that the Digitaria sanguinalis extract and the bacterial culture have an obvious synergistic effect in promoting production. In addition, since rape straw was not added when preparing the carrier in Comparative Example 4, it can be seen that the addition of rape straw, combined with subsequent special treatment methods, can prepare a carrier with excellent production-promoting effects. The inventor speculates that the slow-release effect of Comparative Example 4 should be inferior to that of Examples 1-3, resulting in the macadamia nut trees not being replenished with fertilizer in a timely manner during the long fertilization period. Combining with the experimental results of Experimental Example 1, it can be further speculated that the film-coated corresponding carrier obtained by the present invention can further slow-release the active ingredients, and at the same time, there is a significant synergistic effect among the components in promoting production, making the slow-release fertilizer obtained by the present invention particularly suitable for the cultivation of macadamia nuts.

Claims

1. A preparation method of a slow-release fertilizer for macadamia nuts, characterized in that, The preparation method comprises the following steps: (1) Dissolve chitosan in an acetic acid aqueous solution, then add the Digitaria sanguinalis extract under stirring, incubate at 35-40 °C for 1-2 hours, let stand to remove bubbles, and then cast into a film; wherein, the weight ratio of chitosan to the Digitaria sanguinalis extract is 10:1-3; the Digitaria sanguinalis extract is obtained by a hydrothermal extraction method for Digitaria sanguinalis; (2) Mix Pleurotus eryngii mushroom residue and rape straw in a weight ratio of 3-5:1, place them in an acid solution and soak at 30-40 °C for at least 1 hour, then wash with water until neutral; then add cellulase and carry out enzymatic hydrolysis at 30-35 °C for at least 0.5 hour, and then wash off the residual enzyme with water; then calcine at 600-650 °C to obtain an active ingredient carrier; (3) Uniformly incorporate the Digitaria sanguinalis extract and the mixed bacterial culture into the active ingredient carrier obtained in step (2) in a weight ratio of 2:3-5, and then coat with the film obtained in step (1) to obtain the slow-release fertilizer; The mixed bacterial culture is obtained by mixing Bacillus licheniformis strain 1x2-4 and Frankia fgc6 each cultured in a liquid medium to the plateau phase in a volume ratio of 1:1; the preservation number of Bacillus licheniformis strain 1x2-4 is CGMCC No. 3911, and the preservation number of Frankia fgc6 is CCTCC M207197.

2. The preparation method of a slow-release fertilizer for macadamia nuts according to claim 1, characterized in that, The volume fraction of acetic acid in the acetic acid aqueous solution is 1%, and the weight-to-volume ratio of chitosan to acetic acid is 2 g:1 mL.

3. The preparation method of a slow-release fertilizer for macadamia nuts according to claim 1, characterized in that, The Digitaria sanguinalis extract is prepared by the following hydrothermal extraction method: Add the whole grass of Digitaria sanguinalis to water in a weight-to-volume ratio of 1 g:10 mL, extract at 80 °C for 4 hours, and then rotary evaporate to remove the water to obtain a dry powder.

4. The preparation method of a slow-release fertilizer for macadamia nuts according to claim 1, wherein, In step (1), the incubation temperature is 40 °C and the incubation time is 1 hour.

5. The preparation method of a slow-release macadamia fertilizer according to claim 1, characterized in that, The weight ratio of chitosan to the Digitaria sanguinalis extract is 10:

2.

6. The preparation method of a macadamia slow-release fertilizer according to claim 1, characterized in that, The weight ratio of Pleurotus eryngii mushroom residue to rape straw is 4:

1.

7. The preparation method of a slow-release fertilizer for macadamia nuts according to claim 6, characterized in that, Mix Pleurotus eryngii mushroom residue and rape straw, place them in an acid solution and soak at 40 °C for 2 hours, then wash with water until neutral; then add cellulase and carry out enzymatic hydrolysis at 35 °C for 0.5 hour.

8. The preparation method of a macadamia slow-release fertilizer according to claim 1, characterized in that, In step (2), the calcination temperature is 650 °C and the calcination time is 1 hour.

9. The preparation method of a macadamia slow-release fertilizer according to claim 1, characterized in that, The weight ratio of the Digitaria sanguinalis extract to the mixed bacterial culture is 1:2, and the total weight of the Digitaria sanguinalis extract and the mixed bacterial culture accounts for 10% of the weight of the active ingredient carrier; after coating, the obtained slow-release fertilizer has a film-wrapped outer layer and particles of the Digitaria sanguinalis extract, the mixed bacterial culture and the active ingredient carrier in the inner layer.

10. A macadamia slow-release fertilizer, characterized in that, The slow-release fertilizer is prepared by the preparation method according to any one of claims 1-9.

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