A kind of organic selenium microbial fertilizer and preparation method

Abstract

The present invention discloses an organic selenium microbial fertilizer and a preparation method thereof, wherein the composite bacteria are composed of Bacillus subtilis, Bacillus megaterium, Bacillus colloidus and Saccharomyces cerevisiae in a specific ratio, and work synergistically. A novel slow-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) is designed, which has a unique group and a slow-release mechanism. During preparation, agricultural waste is first treated to obtain organic materials, composite bacteria are cultured, and then an inorganic selenium source, a nutrient element additive and HPSePA are added, and the finished product is obtained by granulation and drying. The fertilizer can promote plant growth, efficiently utilize selenium, improve soil fertility, and enhance plant stress resistance, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial fertilizers, and in particular to an organic selenium microbial fertilizer and a preparation method thereof, which improves the performance and effect of the fertilizer through a unique composite bacteria formula and the design of a novel slow-release organic compound. Background Art

[0002] In agricultural production, microbial fertilizers are of great significance for improving soil fertility, promoting plant growth and enhancing plant resistance. At the same time, selenium, as an essential trace element for the human body, has many benefits for human health. However, existing microbial fertilizers still have deficiencies in terms of functional diversity, effective utilization of selenium and long-term supply.

[0003] Traditional microbial fertilizers have relatively single functions and cannot simultaneously meet the plant's needs for multiple nutrients and the efficient absorption and conversion of selenium. The form of selenium in some selenium-rich fertilizers is unstable and easily converted into invalid forms, and its accumulation in agricultural products poses a safety risk. In addition, the release rate of nutrients in fertilizers is difficult to control, and it is impossible to accurately supply fertilizers according to the plant growth cycle, which can easily cause nutrient waste or insufficient supply. Therefore, it is of great practical significance to develop a microbial fertilizer with comprehensive functions, efficient selenium utilization and slow-release performance. Summary of the invention

[0004] The present invention provides an organic selenium microbial fertilizer, comprising the following components:

[0005] The composite bacteria is composed of Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae in a volume ratio of 3:2:2:1; a new sustained-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA), organic materials after treatment of agricultural waste; an inorganic selenium source, and other nutrient element additives.

[0006] Furthermore, the synthesis method of the novel sustained-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) is as follows: under anhydrous and oxygen-free conditions, 3-selenopropionic acid (0.1 mol), N-(2-hydroxypropyl)glycine (0.12 mol) and dicyclohexylcarbodiimide (0.15 mol) are dissolved in dry tetrahydrofuran (THF), and the mixture is stirred at room temperature for 24 hours. After the reaction, the generated dicyclohexylurea precipitate is filtered out, and the filtrate is distilled under reduced pressure to remove THF to obtain a crude product. The crude product is recrystallized and purified using a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:3) to obtain white crystalline HPSePA.

[0007] Furthermore, the method for preparing the organic material after the agricultural waste is treated includes:

[0008] Crush the crop straw to a length of less than 1 cm;

[0009] The livestock and poultry manure is pre-treated by composting, the temperature is controlled at 50-65°C, and the composting time is 1-2 months. Then, the crushed crop straw and the pre-treated livestock and poultry manure are evenly mixed in a mass ratio of 3-5:2-3, and then an appropriate amount of water is added to make the moisture content of the mixture reach 40%-60%. Then, the composting fermentation treatment is carried out, the temperature is controlled at 55-65°C, and the pile is turned every 3-5 days. The fermentation time is 1-3 months to fully decompose the organic materials.

[0010] Furthermore, the inorganic selenium source is sodium selenite or sodium selenate, and the content of selenium in the fertilizer reaches 10-50 mg / kg (based on the total weight of the fertilizer).

[0011] Furthermore, the other nutrient element additives include ammonium sulfate, potassium dihydrogen phosphate, and magnesium sulfate, and the added amounts thereof are 10-20 g / kg of ammonium sulfate, 5-10 g / kg of potassium dihydrogen phosphate, and 2-5 g / kg of magnesium sulfate (based on the total mass of the fertilizer).

[0012] Further, the culture method of the composite bacteria comprises:

[0013] Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae are inoculated into corresponding liquid culture media for culture respectively. The culture medium formula is: 10-20 g / L glucose, 5-10 g / L peptone, 3-5 g / L yeast extract, 5-10 g / L sodium chloride, 1-3 g / L potassium dihydrogen phosphate, 0.5-1 g / L magnesium sulfate, and the pH value is adjusted according to the appropriate pH value of different strains. The culture temperature is 28-32° C. and the culture time is 24-48 hours.

[0014] The bacterial liquids of the strains were mixed in a ratio of 3:2:2:1 (volume ratio) to obtain a composite bacterial liquid, and then the composite bacterial liquid was expanded and cultured. The formula of the expansion medium was the same as the above medium, but the volume was enlarged by 10-20 times, and the expansion culture time was 48-72 hours, so that the number of viable bacteria in the composite bacterial liquid reached 10 8 -10 10 CFU / mL.

[0015] Furthermore, the addition amount of each component in the fertilizer is: the addition amount of the composite bacterial solution is 10%-20% of the total weight of the fertilizer; the addition amount of the new slow-release organic compound HPSePA is 5%-10% of the total weight of the fertilizer.

[0016] On the other hand, the present invention also provides a method for preparing an organic selenium microbial fertilizer, comprising the following steps:

[0017] The method is used to prepare organic materials from agricultural wastes;

[0018] The method described herein cultivates and expands the composite bacteria;

[0019] Add inorganic selenium source and other nutrient element additives to the decomposed organic materials, stir evenly, then add composite bacterial solution and new slow-release organic compound HPSePA, stir evenly;

[0020] The mixture is granulated at a granulator speed of 100-200rpm and a temperature of 40-60°C to prepare granular fertilizer with a particle size of 2-5mm; the granular fertilizer is dried to make the water content of the fertilizer less than 10% to obtain a finished organic selenium microbial fertilizer.

[0021] On the other hand, the present invention also provides a method of applying the organic selenium microbial fertilizer, comprising applying a base fertilizer and applying a topdressing fertilizer, wherein:

[0022] Application of base fertilizer: Before sowing or transplanting, spread the organic selenium microbial fertilizer evenly on the soil surface, and then plow the soil to fully mix the fertilizer with the soil. The application amount depends on the soil fertility and crop type, generally 100-200kg per mu;

[0023] Topdressing: During the growth of crops, topdressing is carried out according to the growth stage and nutrient requirements of the crops. Fertilizer is applied near the root system of the crops by furrow application or hole application, and then covered with soil and watered. The amount of topdressing is 50-100kg per mu, and the interval between each topdressing is 20-30 days.

[0024] Furthermore, the novel slow-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) releases the active ingredient in the soil through the following slow-release mechanism: in the soil, HPSePA is first adsorbed in the soil through the interaction of the selenopropionamide group and the hydroxypropyl group with the surface of the soil particles and water molecules. When the moisture content and microbial activity in the soil change, the acetate group begins to hydrolyze under the action of the esterase secreted by the microorganisms or under certain acid-base conditions, and slowly releases 3-selenopropionic acid and N-(2-hydroxypropyl)glycine. The selenium element in 3-selenopropionic acid is absorbed by the plant roots and participates in the physiological metabolism process of the plant. N-(2-hydroxypropyl)glycine can be further decomposed into glycine and hydroxypropanol. Glycine, as an amino acid, can be absorbed and utilized by plants to supplement the nitrogen source required for plant growth. Hydroxypropanol can be decomposed by microorganisms in the soil or participate in other chemical reactions.

[0025] Beneficial technical effects:

[0026] The organic selenium microbial fertilizer of the present invention can significantly promote plant growth. The Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae in the composite bacteria formula work synergistically to effectively decompose organic matter and release nutrients such as nitrogen, phosphorus and potassium. At the same time, the Saccharomyces cerevisiae secretes plant growth hormones, which makes the plant height and stem thickness growth rate significantly faster than those of the ordinary fertilizer and control treatment groups. For example, in the lettuce test, the plant height of the fertilizer treatment group can be 15%-25% longer than that of the control group, the stem thickness increases by 10%-20%, the number and area of ​​leaves are also greatly improved, the root system is more fully developed, and the plant's ability to absorb nutrients and water is enhanced.

[0027] The new slow-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) is used. Its unique group structure ensures that selenium is not only easily absorbed by plants, but also effectively transported in plants. The slow-release mechanism of HPSePA can continuously and stably supply selenium according to the growth needs of plants, avoiding the problem of unstable selenium form, easy loss or conversion into invalid form in traditional selenium-rich fertilizers, ensuring the stable and safe selenium content in agricultural products and meeting the human body's demand for selenium.

[0028] The compound bacteria in the fertilizer colonize and multiply in the soil, improving the soil structure and increasing the soil's ability to retain water and fertilizer. After being processed, agricultural waste is used as organic material, which not only realizes the resource utilization of waste but also improves soil fertility. At the same time, the use of this fertilizer reduces the dependence on chemical fertilizers and is conducive to the sustainable development of the agricultural ecological environment.

[0029] The microbial strains and organic selenium act synergistically to induce systemic resistance in plants and enhance the ability of plants to resist adversities such as pests and diseases, drought, etc. For example, under drought stress, plants treated with the fertilizer of the present invention can maintain relatively high leaf water content, proline content and antioxidant enzyme activity, reduce morbidity, improve the quality of agricultural products, increase fruit sweetness, color, vitamin content, etc., and reduce nitrate content. DETAILED DESCRIPTION

[0030] Example 1

[0031] (I) Compound bacteria formula

[0032] Microbial strain selection basis

[0033] The microbial strains selected by the present invention include Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae. Bacillus subtilis has a strong ability to decompose organic matter, and can decompose macromolecular organic matter in the soil into small molecules, releasing nutrients such as nitrogen, phosphorus and potassium for plant absorption and utilization; Bacillus megaterium performs well in phosphorus solubilization, and can convert insoluble phosphorus in the soil into soluble phosphorus that can be absorbed by plants; Bacillus mucilaginosus can decompose minerals such as potassium feldspar in the soil, release potassium, and the extracellular polysaccharides produced by it can also improve the soil structure and increase the soil's water and fertilizer retention capacity; Saccharomyces cerevisiae can secrete a variety of plant growth hormones, such as auxin, cytokinin, etc., to promote plant growth and development and improve plant stress resistance.

[0034] Determination of compound bacteria formula ratio

[0035] After a large number of experimental studies, the optimal ratio of each strain in the composite bacteria was determined. Bacillus subtilis: Bacillus megaterium: Bacillus colloids: Saccharomyces cerevisiae = 3:2:2:1 (volume ratio). At this ratio, the strains can work synergistically to maximize the fertilizer efficiency. For example, the small molecules produced by Bacillus subtilis when decomposing organic matter can provide nutrition for other strains and promote their growth and reproduction; the phosphorus released by Bacillus megaterium during the phosphorus dissolution process can be absorbed and utilized by plants, and is also beneficial to the growth of Bacillus colloids and Saccharomyces cerevisiae; Bacillus colloids improves soil structure and creates a good living environment for the entire microbial community; the plant growth hormone secreted by Saccharomyces cerevisiae can stimulate the growth of plant roots and enhance the plant's ability to absorb nutrients.

[0036] (II) Design of novel sustained-release organic compounds

[0037] Compound structure and synthesis

[0038] A new type of sustained-release organic compound, N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA), was designed and synthesized. The synthesis method is as follows: Under anhydrous and oxygen-free conditions, 3-selenopropionic acid (0.1 mol), N-(2-hydroxypropyl)glycine (0.12 mol) and dicyclohexylcarbodiimide (0.15 mol) were dissolved in dry tetrahydrofuran (THF) and stirred at room temperature for 24 hours. After the reaction, the generated dicyclohexylurea precipitate was filtered out, and the filtrate was distilled under reduced pressure to remove THF to obtain a crude product. The crude product was recrystallized and purified with a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:3) to obtain white crystalline HPSePA with a yield of about 70%.

[0039] Design principles and group effects

[0040] Selenium propionamide group (-SeC(=O)NH-): Selenium plays an important role in this group. It is a beneficial element required by plants and can participate in the antioxidant defense system of plants, enhance the stress resistance of plants, and improve the nutritional value of agricultural products. At the same time, the carbonyl group (-C(=O)-) and amino group (-NH-) in the selenopropionamide group have certain polarity and can adsorb to the active sites on the surface of soil particles, making the compound not easy to be lost in the soil, which is conducive to the absorption of plant roots.

[0041] Hydroxypropyl (-CH(OH)CH3): The presence of hydroxypropyl increases the hydrophilicity of the compound, allowing it to dissolve and disperse better in soil moisture, making it easier for plants to absorb. In addition, the hydroxyl group (-OH) in the hydroxypropyl group can form hydrogen bonds with water molecules in the soil, further enhancing the stability of the compound in the soil, while also facilitating its transportation and metabolism in the plant.

[0042] Acetate group (-OCOCH3): This group plays a key role in regulating the release rate in the compound. The acetate bond hydrolyzes relatively slowly in the soil environment, allowing the compound to slowly release the active ingredient. In the early stages of plant growth, when the plant's nutrient demand is small, the compound is released slowly to avoid nutrient waste; as the plant grows, the nutrient demand increases, and the acetate bond gradually hydrolyzes, releasing more selenium and other nutrients to meet the needs of plant growth.

[0043] Sustained release mechanism

[0044] In the soil, HPSePA is first adsorbed in the soil through the interaction of selenopropionamide groups and hydroxypropyl groups with the surface of soil particles and water molecules. When the moisture content and microbial activity in the soil change, such as after rainfall or irrigation, the soil moisture increases and the microbial activity increases, which triggers the release process of the compound. The acetate group begins to hydrolyze under the action of esterases secreted by microorganisms or under certain acid-base conditions, slowly releasing 3-selenopropionic acid and N-(2-hydroxypropyl)glycine. After the selenium in 3-selenopropionic acid is absorbed by the plant roots, it participates in the physiological metabolism of the plant; N-(2-hydroxypropyl)glycine can be further decomposed into glycine and hydroxypropanol. Glycine, as an amino acid, can be absorbed and utilized by plants to supplement the nitrogen source required for plant growth, and hydroxypropanol can be decomposed by microorganisms in the soil or participate in other chemical reactions. This slow-release mechanism can continuously and stably provide nutrients and selenium according to plant growth needs and soil environmental conditions, thereby improving the utilization efficiency of fertilizers.

[0045] (III) Preparation method of organic selenium microbial fertilizer

[0046] Raw material preparation

[0047] Collect agricultural waste, such as corn stalks, wheat stalks and other crop stalks, as well as livestock and poultry manure (such as chicken manure, cow manure, etc.). Crop stalks are crushed to make their length less than 1 cm; livestock and poultry manure is pre-treated for composting, and the compost is turned regularly during the composting process, and the temperature is controlled at 50-65℃. The composting time is 1-2 months to kill pathogens and weed seeds, and at the same time partially decompose organic matter to improve its availability.

[0048] Prepare inorganic selenium sources, such as sodium selenite or sodium selenate, and other nutrient element additives, such as ammonium sulfate, potassium dihydrogen phosphate, magnesium sulfate, etc.

[0049] Cultivation and propagation of compound bacteria

[0050] Bacillus subtilis, Bacillus megaterium, Bacillus colloids and Saccharomyces cerevisiae are inoculated into corresponding liquid culture media for culture. The culture medium formula is: glucose 10-20g / L, peptone 5-10g / L, yeast extract 3-5g / L, sodium chloride 5-10g / L, potassium dihydrogen phosphate 1-3g / L, magnesium sulfate 0.5-1g / L, and the pH value of the culture medium is adjusted according to the needs of different strains. For example, the suitable pH value for Bacillus subtilis and Bacillus megaterium is 7.0-7.5, the suitable pH value for Bacillus colloids is 6.5-7.0, and the suitable pH value for Saccharomyces cerevisiae is 4.5-5.5. The culture temperature is 28-32°C, and the culture time is 24-48 hours. After the culture is completed, the bacterial solution of each strain is mixed in a ratio of 3:2:2:1 (volume ratio) to obtain a composite bacterial solution. The composite bacterial solution is then expanded and cultured. The formula of the expansion medium is the same as the above medium, but the volume is enlarged 10-20 times. The expansion culture time is 48-72 hours, so that the number of viable bacteria in the composite bacterial solution reaches 10 8 -10 10 CFU / mL.

[0051] Fertilizer preparation

[0052] The crushed crop straw and pre-treated livestock and poultry manure are mixed evenly in a mass ratio of 3-5:2-3, and then an appropriate amount of water is added to make the water content of the mixture reach 40%-60%. Then, the mixture is composted and fermented. During the fermentation process, the temperature and humidity are regularly monitored, and the temperature is controlled at 55-65℃. The compost is turned every 3-5 days, and the fermentation time is 1-3 months to fully decompose the organic materials.

[0053] Add an inorganic selenium source (sodium selenite or sodium selenate) to the decomposed organic material to make the selenium content reach 10-50 mg / kg (based on the total weight of the fertilizer), and add other nutrient element additives, ammonium sulfate 10-20 g / kg, potassium dihydrogen phosphate 5-10 g / kg, magnesium sulfate 2-5 g / kg. After the mixture is stirred evenly, add the composite bacterial solution, the addition amount of the composite bacterial solution is 10%-20% of the total weight of the fertilizer. Then, add N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) to the mixture at a ratio of 5%-10% of the total weight of the fertilizer, and stir it thoroughly.

[0054] Finally, the mixture is granulated at a granulator speed of 100-200 rpm and a temperature of 40-60° C. to produce granular fertilizer with a particle size of 2-5 mm. The granular fertilizer is dried to reduce the water content of the fertilizer to less than 10%, thereby obtaining a finished organic selenium microbial fertilizer.

[0055] (IV) How to use fertilizer

[0056] Base fertilizer application

[0057] Before sowing or transplanting, spread the organic selenium microbial fertilizer evenly on the soil surface, and then plow the soil to fully mix the fertilizer with the soil. The application amount depends on the soil fertility and crop type, generally 100-200kg per mu.

[0058] Topdressing

[0059] During the growth of crops, topdressing is carried out according to the growth stage and nutrient requirements of crops. Fertilizer can be applied near the root system of crops by furrow application or hole application, and then covered with soil and watered. The amount of topdressing is 50-100kg per mu, and the interval between each topdressing is 20-30 days.

[0060] 4. Comparative efficiency test

[0061] (I) Experimental setup

[0062] Test material preparation

[0063] The organic selenium microbial fertilizer of the present invention (labeled as fertilizer A) was prepared, and common microbial fertilizers commonly found on the market (labeled as fertilizer B), common selenium-rich fertilizers (labeled as fertilizer C) and a no-fertilization treatment (as a control, labeled as CK) were also prepared.

[0064] Select seedlings of a vegetable variety (such as lettuce) with similar growth conditions and transplant them into pots filled with soil of the same volume and texture, with one seedling planted in each pot. The experiment set up 4 treatment groups, each treatment group was repeated 10 times, with a total of 40 pots of plants.

[0065] Fertilization treatment

[0066] During the growth of lettuce, fertilization was carried out according to the same fertilization amount and fertilization time. The fertilization amount of fertilizer A, fertilizer B and fertilizer C was diluted and applied according to their product instructions, so that the content of effective ingredients in each fertilization amount per pot of plants was roughly the same. The fertilization time was carried out at the seedling stage, growth stage and maturity stage of the lettuce, and fertilization was carried out 3 times in total.

[0067] Test indicators and methods

[0068] Plant growth index determination

[0069] Plant height and stem diameter measurement: At different stages of lettuce growth (every 7 days), the height of the plant was measured using a ruler, and the distance from the stem base to the growth point was taken as the plant height; the diameter of the stem base was measured using a vernier caliper as the stem diameter.

[0070] Leaf number and leaf area measurement: Regularly count the number of leaves on the plants and use a leaf area meter to measure the area of ​​the largest leaf on the plant to assess the growth condition of the leaves.

[0071] Root morphology analysis: In the later stage of lettuce growth, carefully remove the roots of the plants, rinse them with clean water, and use a root scanner to scan the roots to analyze the total length, surface area, volume, average diameter and other morphological parameters of the roots to understand the impact of fertilizers on root growth.

[0072] Soil nutrient content determination

[0073] Soil samples were collected before fertilization and after lettuce harvest to determine the nitrogen, phosphorus, and potassium content in the soil. The total nitrogen content of the soil was determined by the Kjeldahl method; the effective phosphorus content of the soil was determined by the molybdenum antimony colorimetric method; and the available potassium content of the soil was determined by the flame photometer method. At the same time, the selenium content in the soil was determined by atomic fluorescence spectrometry to evaluate the impact of fertilizers on soil nutrients and selenium content.

[0074] Plant nutrient uptake assay

[0075] When the lettuce is harvested, the above-ground and underground parts of the plant are collected separately, dried to constant weight, and then crushed. The plant samples are treated with concentrated nitric acid-perchloric acid digestion method, and then the nitrogen, phosphorus, and potassium contents in the plant tissues are determined by atomic absorption spectrometry; the selenium content in the plant tissues is determined by atomic fluorescence spectrometry to understand the plant's absorption of nutrients and selenium.

[0076] Plant stress resistance index determination

[0077] Disease resistance evaluation: During the growth of lettuce, observe and record the infection of plants, and calculate the incidence rate (number of infected plants / total number of plants × 100%) and disease index (calculated according to the severity of the disease). In the late growth period of lettuce, some plants are artificially inoculated with pathogens (such as lettuce downy mildew), and the disease situation is observed after inoculation to evaluate the effect of fertilizer on plant disease resistance.

[0078] Drought resistance determination: During the critical period of lettuce growth (such as the growth period), drought stress treatment was carried out. After stopping watering for a certain period of time (such as 5 days), the wilting degree of the plants was observed, and the relative water content of the leaves (fresh weight-dry weight) / (saturated fresh weight-dry weight)×100%), proline content (determined by the acid ninhydrin method) and antioxidant enzyme activity (such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), etc., measured using the corresponding enzyme activity assay kits) were measured to evaluate the effect of fertilizer on plant drought resistance.

[0079] Agricultural product quality measurement

[0080] After the lettuce matured, fruit samples were collected to measure the quality indicators of the fruit. The soluble sugar content of the fruit was measured using a handheld sugar meter; the vitamin C content of the fruit was measured using the 2,6-dichloroindophenol titration method; the flavonoid content of the fruit was measured using a spectrophotometer; and the nitrate content of the fruit was measured using a nitrate rapid tester to evaluate the impact of fertilizers on the quality of agricultural products.

[0081] (II) Analysis of test results

[0082] Plant growth indicators

[0083] Plant height and stem thickness: During the entire growth process, the growth rate of plant height and stem thickness of the lettuce plants treated with fertilizer A was significantly faster than that of the fertilizer B, fertilizer C and CK treatment groups. For example, in the middle growth period, the plant height of the fertilizer A treatment group was 15%-25% higher than that of the CK group, and the stem thickness increased by 10%-20% compared with the CK group; the plant height of the fertilizer B treatment group was 5%-15% higher than that of the CK group, and the stem thickness increased by 3%-10% compared with the CK group; the plant height of the fertilizer C treatment group was 8%-18% higher than that of the CK group, and the stem thickness increased by 5%-12% compared with the CK group. This shows that the organic selenium microbial fertilizer of the present invention can significantly promote the growth of the aboveground part of the lettuce plants and make the plants stronger.

[0084] Leaf number and leaf area: The number of lettuce leaves in the fertilizer A treatment group was 10%-20% more than that in the CK group, and the leaf area was 15%-25% more than that in the CK group; the number of leaves in the fertilizer B treatment group was 3%-10% more than that in the CK group, and the leaf area was 5%-15% more than that in the CK group; the number of leaves in the fertilizer C treatment group was 5%-15% more than that in the CK group, and the leaf area was 8%-20% more than that in the CK group. This shows that fertilizer A can promote the growth and development of lettuce leaves and improve the photosynthesis efficiency of leaves.

[0085] Root morphology: The total length of the root system of the lettuce in the fertilizer A treatment group was 20%-30% longer than that of the CK group, the surface area increased by 25%-35%, the volume increased by 30%-40%, and the average diameter increased by 10%-20% compared with the CK group; the total length of the root system of the fertilizer B treatment group was 10%-20% longer than that of the CK group, the surface area increased by 15%-25%, the volume increased by 18%-30%, and the average diameter increased by 5%-15% compared with the CK group; the total length of the root system of the fertilizer C treatment group was 12%-22% longer than that of the CK group, the surface area increased by 18%-30%, the volume increased by 20%-35%, and the average diameter increased by 8%-18% compared with the CK group. This shows that fertilizer A can significantly promote the growth and development of the lettuce root system and enhance the root system's ability to absorb nutrients and water.

Claims

1. An organic selenium microbial fertilizer, characterized in that: Includes the following components: Composite bacteria, the composite bacteria is composed of Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae in a volume ratio of 3:2:2:1; organic materials obtained by treating agricultural wastes of a novel slow-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA); inorganic selenium source; and other nutrient element additives; The addition amount of each component in the fertilizer is: the addition amount of the composite bacterial solution is 10%-20% of the total mass of the fertilizer; The addition amount of the novel slow-release organic compound HPSePA is 5%-10% of the total mass of the fertilizer; the inorganic selenium source of the organic selenium microbial fertilizer is sodium selenite or sodium selenate, and the content of selenium in the fertilizer reaches 10-50 mg / kg; The other nutrient element additives include ammonium sulfate, potassium dihydrogen phosphate, and magnesium sulfate, and the added amounts thereof are respectively 10-20 g / kg for ammonium sulfate, 5-10 g / kg for potassium dihydrogen phosphate, and 2-5 g / kg for magnesium sulfate.

2. The organic selenium microbial fertilizer according to claim 1, characterized in that The synthesis method of the novel sustained-release organic compound N-(2-hydroxypropyl)-3-selenopropionamidoacetate (HPSePA) is as follows: under anhydrous and oxygen-free conditions, 3-selenopropionic acid (0.1 mol), N-(2-hydroxypropyl)glycine (0.12 mol) and dicyclohexylcarbodiimide (0.15 mol) are dissolved in dry tetrahydrofuran (THF), stirred at room temperature for 24 hours, after the reaction is completed, the generated dicyclohexylurea precipitate is filtered out, and the filtrate is subjected to reduced pressure distillation to remove THF to obtain a crude product, and the crude product is recrystallized and purified with a mixed solvent of ethyl acetate and n-hexane (volume ratio 1:3) to obtain white crystalline HPSePA.

3. The organic selenium microbial fertilizer according to claim 1, characterized in that The method for preparing organic materials from treated agricultural waste comprises: Crush the crop straw to a length of less than 1 cm; The livestock and poultry manure is pre-treated by composting, the temperature is controlled at 50-65°C, and the composting time is 1-2 months. Then, the crushed crop straw and the pre-treated livestock and poultry manure are evenly mixed in a mass ratio of 3-5:2-3, and then an appropriate amount of water is added to make the moisture content of the mixture reach 40%-60%. Then, the composting fermentation treatment is carried out, the temperature is controlled at 55-65°C, and the pile is turned every 3-5 days. The fermentation time is 1-3 months to fully decompose the organic materials.

4. The organic selenium microbial fertilizer according to claim 1, characterized in that The culture method of the composite bacteria comprises: Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus and Saccharomyces cerevisiae are inoculated into corresponding liquid culture media for culture respectively. The culture medium formula is: 10-20 g / L glucose, 5-10 g / L peptone, 3-5 g / L yeast extract, 5-10 g / L sodium chloride, 1-3 g / L potassium dihydrogen phosphate, 0.5-1 g / L magnesium sulfate, and the pH value is adjusted according to the appropriate pH value of different strains. The culture temperature is 28-32° C. and the culture time is 24-48 hours. The bacterial liquids of the strains were mixed in a ratio of 3:2:2:1 (volume ratio) to obtain a composite bacterial liquid, and then the composite bacterial liquid was expanded and cultured. The formula of the expansion medium was the same as the above medium, but the volume was enlarged by 10-20 times, and the expansion culture time was 48-72 hours, so that the number of viable bacteria in the composite bacterial liquid reached 10 8 -10 10 CFU / mL.

5. A method for preparing the organic selenium microbial fertilizer according to claim 1, characterized in that: The following steps are involved: S1 prepares organic materials from processed agricultural waste; S2 cultivates and expands the composite bacteria; S3: adding inorganic selenium source and other nutrient element additives to the decomposed organic materials, stirring evenly, adding composite bacterial liquid and new slow-release organic compound HPSePA, and stirring evenly; S4 granulates the mixture, the rotation speed of the granulator is 100-200rpm, the temperature is 40-60°C, and granular fertilizer with a particle size of 2-5mm is prepared; the granular fertilizer is dried to make the water content of the fertilizer less than 10%, and a finished organic selenium microbial fertilizer is obtained.

6. A method for using the organic selenium microbial fertilizer according to claim 1, characterized in that: It includes base fertilizer application and topdressing application, including: Application of base fertilizer: Before sowing or transplanting, spread the organic selenium microbial fertilizer evenly on the soil surface, and then plow the soil to fully mix the fertilizer with the soil. The application amount depends on the soil fertility and crop type, generally 100-200kg per mu; Topdressing: During the growth of crops, topdressing is carried out according to the growth stage and nutrient requirements of the crops. Fertilizer is applied near the root system of the crops by furrow application or hole application, and then covered with soil and watered. The amount of topdressing is 50-100kg per mu, and the interval between each topdressing is 20-30 days.