Slow-release compound fertilizer prepared by utilizing camellia oleifera shell cell structure

Abstract

The invention belongs to the field of agricultural waste recycling, and discloses a slow-release compound fertilizer prepared by utilizing a camellia oleifera shell cell structure, and a preparation method of the slow-release compound fertilizer comprises the following steps: removing impurities to obtain a camellia oleifera shell raw material, crushing, drying to obtain a shell base material, fully dipping in molten urea, filtering, and cooling to obtain the compound fertilizer. The compound fertilizer disclosed by the invention is simple in whole preparation process, high in repeatability and relatively low in equipment requirement. The compound fertilizer has high application value in the agricultural field, the added value of the camellia oleifera shells can be remarkably improved, and the economic income of farmers is increased. Due to the remarkable structural difference between parenchyma cells and thick-walled cell walls of the camellia oleifera shells, the prepared organic and inorganic nutrient slow-release compound fertilizer can efficiently store urea without additional high-temperature carbonization pore-forming, on the other hand, the high-temperature molten urea can react with hemicellulose carboxyl functional groups of the camellia oleifera shells to realize fixation of nitrogen, and the nitrogen fixation effect is improved. Therefore, intelligent release of nutrients is further realized to promote crop growth.

Description

Technical Field

[0001] The invention belongs to the field of agricultural waste resource utilization, and particularly relates to an organic and inorganic nutrient slow-release compound fertilizer prepared by utilizing the cell structure of oil-tea camellia shells. Background Art

[0002] The oil-tea camellia industry in China is a vital component of the agricultural economy. Camellia oleifera is a woody oil plant unique to China, and its seeds can be used to produce high-quality tea oil. In recent years, the area cultivated for oil-tea camellia has continued to expand, and production has increased annually, generating over 3 million tons of husk waste annually. However, supporting husk waste treatment technologies have not developed in tandem. Failure to properly treat large quantities of husk waste can pollute soil, water, and air, while also causing economic losses for growers. The husk, with its petal-like structure and light weight, is characterized by its rigidity and richness. It contains a large number of both thick-walled and thin-walled cells. The thick-walled cells have prominent secondary thickening, while the thin-walled cells are thin but contain large cavities. These cell wall structures differ significantly, yet there is a lack of agricultural applications based on this cellular structure. The large-scale utilization of husk as an agricultural input effectively extends the oil-tea industry chain, increasing the added value of the industry, improving the agricultural ecosystem, and reducing the burden of environmental pollution. It can also create significant ecological, economic, and social benefits, offering a valuable way for farmers to dispose of husk waste and increase their income.

[0003] With the continuous development of society, especially the rapid growth of agriculture, farmers are becoming increasingly dependent on fertilizers. Long-term excessive use of chemical fertilizers can lead to soil compaction, reduced soil aeration and water retention, soil acidification, and excessive salinity, which in turn affects crop growth. Land degradation caused by fertilizer dependence reduces land productivity and threatens food security. Organic-inorganic compound fertilizers combine the advantages of organic matter and inorganic nutrients to provide a comprehensive nutritional supply for crops. The production process of organic-inorganic compound fertilizers is relatively complex, involving pretreatment of organic materials (such as drying, pulverization, and harmless treatment), mixing with inorganic fertilizers, and granulation. The relatively high costs of collecting, handling, and processing organic materials contribute to the high production costs of organic-inorganic compound fertilizers. Furthermore, the rate of nutrient release in organic-inorganic compound fertilizers is difficult to control. Using tea oil fruit shells, a large-scale solid waste, to replace the organic component in organic-inorganic compound fertilizers can effectively address the industry's problem of high organic raw material prices.

[0004] Urea is a fast-acting nitrogen fertilizer. If crops can't absorb it quickly, nitrogen can be lost, resulting in both waste and environmental pollution. Using porous materials (such as bentonite and zeolite) as carriers, molten urea is evenly loaded into the carrier's pores through an impregnation process, creating an "adsorption-slow-release" mechanism that significantly extends the fertilizer's nutrient release cycle and optimizes urea utilization. Inorganic porous materials are poorly biodegradable, and long-term use can adversely affect soil quality. Organic matter, on the other hand, generally requires carbonization to form a porous structure that can effectively load molten urea. For example, Chinese patent application CN104817378A discloses a method for producing bamboo biochar-based urea. This method includes the following steps: pyrolysis of bamboo to produce bamboo biochar and combustible gas; mixing the urea raw material with bamboo biochar, which accounts for 12-16% of the total urea raw material weight, followed by melting, granulation, and collection of the granules; negative pressure cooling of the collected granules and screening; coating the screened granules, packaging, and shipping to produce bamboo biochar-based urea. CN107586220A discloses a method for producing biochar-based urea fertilizer by infiltration and fusion. This method includes the following steps: preparing the raw materials; infiltration of the biochar and urea by melting; and rapid cooling to produce the fertilizer. The main fertilization process involves preheating the urea powder and biochar powder, controlling the system temperature to the urea melting temperature, and achieving complete infiltration and fusion of the urea melt and biochar powder. Finally, cooling produces the biochar-based urea fertilizer. This carbonization process not only destroys organic matter but also incurs high costs.

[0005] How to prepare slow-release nitrogen fertilizer at low cost and efficiently utilize tea oil shells is a challenging task. Summary of the Invention

[0006] The object of the present invention is to overcome at least one shortcoming of the prior art and provide a camellia oleifera shell-based organic and inorganic nutrient slow-release compound fertilizer.

[0007] The technical solution adopted by the present invention is: The first aspect of the present invention provides: A slow-release compound fertilizer prepared using the cell structure of camellia oleifera shells, the preparation method of which comprises the following steps: 1) Cleaning the oil-pressing waste from camellia seeds to remove non-camellia shell debris and obtain camellia shell raw materials; 2) crushing and drying the camellia oleifera shell raw material to obtain the shell substrate; 3) The fruit shell substrate is fully immersed in molten urea, and then filtered and cooled to obtain a camellia oleifera fruit shell-based organic and inorganic nutrient slow-release compound fertilizer.

[0008] In some examples, the oil-tea camellia shell raw material is crushed to a particle size of 0.2 cm to 1.5 cm.

[0009] In some examples, the fruit shell substrate is heated to 120° C. to 180° C. and then mixed with molten urea and impregnated.

[0010] In some examples, the fruit shell substrate is heated for 0.5 h to 3 h.

[0011] In some examples, the immersion time is 0.2 h to 2 h.

[0012] In some examples, the immersion temperature is 135°C to 170°C.

[0013] In some embodiments, the drying temperature of the oil-tea camellia shell raw material is 60°C to 120°C.

[0014] In some examples, the drying time of the camellia oleifera shell raw material is 12 h to 48 h.

[0015] In some examples, the mass mixing ratio of the fruit shell substrate to the molten urea is 1: (1-6).

[0016] The above features can be combined arbitrarily unless they conflict with each other.

[0017] The second aspect of the present invention provides: The first aspect of the present invention is the use of a camellia oleifera shell-based organic and inorganic nutrient slow-release compound fertilizer in soil improvement.

[0018] The beneficial effects of the present invention are: The present invention provides a low-cost method for preparing a slow-release organic-inorganic nutrient compound fertilizer using the cell structure of camellia oleifera shells. The organic-inorganic nutrient slow-release compound fertilizer is prepared using camellia oleifera shells, a low-cost, renewable, and environmentally friendly byproduct of camellia oil seed oil extraction, as the base. The entire preparation process is simple, highly reproducible, and requires minimal equipment. This compound fertilizer has high application value in the agricultural sector, significantly increasing the added value of camellia oleifera shells and boosting farmers' income.

[0019] The present invention provides a slow-release organic and inorganic nutrient compound fertilizer prepared using the cell structure of camellia oleifera shells. Due to the significant structural differences between the parenchyma and sclerenchyma cell walls of camellia oleifera shells, the prepared slow-release organic and inorganic nutrient compound fertilizer can efficiently store urea without the need for additional high-temperature carbonization and pore formation. Furthermore, the high-temperature melted urea reacts with the carboxyl functional groups of the hemicellulose in the camellia oleifera shells to fix nitrogen, further enabling intelligent nutrient release to promote crop growth.

[0020] The present invention provides an organic-inorganic nutrient slow-release compound fertilizer prepared using the cell structure of oil-tea camellia shells. Thanks to the high organic matter content of the shells, the compound fertilizer has the function of rapidly regulating the dissolved organic matter in the soil. It can achieve structural improvement of the dissolved organic matter in the soil while ensuring the supply of crop nutrients, thereby increasing the content of humus-like substances in the dissolved organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram of the tissue and cell structure of the oil-tea camellia shell.

[0022] Figure 2 This is a cross-sectional view of the oil-tea camellia fruit-based organic and inorganic nutrient slow-release material.

[0023] Figure 3 This is the nutrient slow-release curve of Example 2.

[0024] Figure 4 This is the cross-sectional view of the slow-release fertilizer based on oil-tea camellia shell after slow release (above) and the distribution of nitrogen in the cross-sectional view (below).

[0025] Figure 5 This is the crop growth situation of Example 2.

[0026] Figure 6 This is the three-dimensional fluorescence spectrum of soil dissolved organic matter in Example 2.

[0027] Figure 7 This is a chart showing the proportion of each component of soil dissolved organic matter in Example 2. DETAILED DESCRIPTION

[0028] An organic and inorganic nutrient slow-release compound fertilizer prepared using the cell structure of oil-tea camellia shells, the preparation method of which comprises the following steps: 1) Cleaning the oil-pressing waste from camellia seeds to remove non-camellia shell debris and obtain camellia shell raw materials; 2) crushing and drying the camellia oleifera shell raw material to obtain the shell substrate; 3) The fruit shell substrate is fully immersed in molten urea, and then filtered and cooled to obtain a camellia oleifera fruit shell-based organic and inorganic nutrient slow-release compound fertilizer.

[0029] In some embodiments, the oil-tea camellia shell raw material is crushed to a particle size of 0.2 cm to 1.5 cm, which can help obtain a more effective compound fertilizer.

[0030] In some embodiments, the fruit shell substrate is heated to 120° C. to 180° C. before being mixed and impregnated with the molten urea. This is more conducive to the fixation of urea on the fruit shell substrate through physical adsorption and chemical reaction.

[0031] In some examples, the fruit shell substrate is heated to 120°C to 180°C before being mixed with molten urea and impregnated for 0.5 to 3 hours. This allows for more complete drying of the fruit shell substrate, facilitating subsequent impregnation and reaction.

[0032] In some examples, the immersion time is 0.2 h to 2 h, which allows for sufficient immersion and reaction.

[0033] In some examples, the impregnation temperature is 135° C. to 170° C. This is more conducive to impregnation and reaction.

[0034] In some embodiments, the drying temperature of the oil-tea camellia shell raw material is 60°C to 120°C.

[0035] In some examples, the drying time of the camellia oleifera shell raw material is 12 h to 48 h.

[0036] The mass ratio of the fruit shell substrate to the molten urea can be adjusted as needed. A higher amount of urea results in more urea on the surface of the compound fertilizer, allowing for faster nitrogen replenishment and subsequent sustained release. In some embodiments, the mass ratio of the fruit shell substrate to the molten urea is 1:(1-6).

[0037] The above features can be combined arbitrarily unless they conflict with each other.

[0038] The following will clearly and completely describe the concept and technical effects of the present invention with reference to examples, so as to fully illustrate the purpose, features, and effects of the present invention. The examples described are only some examples of the present invention, not all examples. Based on the examples of the present invention, other examples obtained by those skilled in the art without inventive effort shall fall within the scope of protection of the present invention.

[0039] Example 1 1) Remove impurities such as fallen leaves, branches, fruit stems, gravel, etc. from the leftover materials from camellia oil pressing; 2) crushing the camellia husk to obtain camellia husk substrate particles of 0.2 cm to 0.5 cm, and then drying the particles at 105°C for 24 hours to obtain dried camellia husk substrate particles; 3) heating the dried camellia shell substrate obtained in step 2) to 155°C and then impregnating it with 150°C molten urea at a mass ratio of 1:1.5 at an ambient temperature of 150°C for 0.5 h; 4) filtering the solid-liquid mixture obtained in step 3) within 0.2 h and cooling it for 24 h to obtain a camellia shell-based organic and inorganic nutrient slow-release compound fertilizer for providing nutrients to crops and improving soil.

[0040] Example 2 1) Remove impurities such as fallen leaves, branches, fruit stems, gravel, etc. from the leftover materials from camellia oil pressing; 2) crushing the camellia husk to obtain camellia husk substrate particles of 0.6 cm to 0.7 cm, and then drying the particles at 105°C for 24 hours to obtain dried camellia husk substrate particles; 3) heating the dried camellia shell substrate obtained in step 2) to 160°C and then impregnating it with 160°C molten urea at a mass ratio of 1:2 at an ambient temperature of 160°C for 0.5 h; 4) filtering the solid-liquid mixture obtained in step 3) within 0.3 h and cooling it for 5 h to obtain a camellia shell-based organic and inorganic nutrient slow-release compound fertilizer for providing nutrients to crops and improving soil.

[0041] Example 3 Refer to Example 2, except that the fertilizer prepared in this example uses camellia oleifera shell substrate particles of 0.2-0.3 cm, the molten urea impregnation temperature is 140°C, and the loading time is 0.1 h.

[0042] Example 4 Refer to Example 2, except that the oil tea shell substrate particles used in the fertilizer prepared in this example are 0.3-0.4 cm, and the dried oil tea shell substrate is heated to 150°C and then impregnated with 150°C molten urea in a mass ratio of 1:3 at an ambient temperature of 165°C.

[0043] The following are the test results of the 24-hour cumulative nitrogen release of the root system and stem length of corn seedlings 28 days after fertilization and the static water release as shown in Table 1.

[0044] Table 1. Comparison of the effects of different compound fertilizers deal with Corn root length (cm) Corn stalk length (cm) Cumulative nitrogen release in 24 hours (%) Example 2 22.0 37.17 40.27% Example 3 15.1 28.5 95.3% Example 4 18.2 27.3 84.2% By comparing Examples 2 to 4, it can be seen that after using the compound fertilizer of Example 2, the root length and stem length of the corn seedlings are both longer than those of Examples 3 and 4, and the cumulative N release in 24 hours is significantly lower than that of Examples 3 and 4, which can better promote the growth of corn seedlings and achieve the effect of slow nutrient release. By comparing Example 2 with Examples 3 and 4, it can be seen that when the particle size of the oil-tea camellia shell substrate particles is too small, the immersion time is too low, and the proportion of urea is higher, it is difficult for urea to be effectively loaded on the oil-tea camellia shell substrate particles, and the cumulative N release in 24 hours is too large. As can be seen from the data in Table 1, the N release rate of the compound fertilizer can be adjusted by controlling the particle size of the oil-tea camellia shell substrate particles, the immersion time, and the mixing ratio of the oil-tea camellia shell substrate particles and urea to meet the N requirements of different crops at different stages.

[0045] Characterization and performance testing To better illustrate the present invention, a 28-day corn pot experiment was conducted. Agronomic efficacy test was conducted using a 1g urea-containing slow-release compound fertilizer based on camellia oleifera shells. The soil dissolved organic matter composition was measured using a three-dimensional fluorescence spectrometer. The hydrostatic nutrient slow-release performance of the slow-release compound fertilizer based on camellia oleifera shells was determined using an ultraviolet spectrophotometer. Cross-sections of the husk-based particles and the slow-release compound fertilizer based on camellia oleifera shells were examined using a scanning electron microscope. Using 1g of pure urea as a comparison, changes in soil dissolved organic matter and crop growth were measured while maintaining all other treatments unchanged.

[0046] Figure 1 This is a diagram of the tissue and cell structure of the oil-tea camellia shell. Figure 1 It can be seen that the oil-tea camellia shell contains obvious thick-walled cells and thin-walled cells. Figure 2 This is a cross-sectional view of Example 2 Camellia oleifera-based organic and inorganic nutrient slow-release material, consisting of Figure 2 It can be seen that after the melt impregnation treatment, urea fills the cell tissue of the oil-tea camellia shell, and the urea can be effectively stored in the cell cavity and cell wall. The present invention can effectively utilize the cell tissue characteristics of the oil-tea camellia shell to store urea. Figure 3 is the nutrient release curve of Example 2, Figure 3 It can be seen that the oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer slows down the 24-hour release of urea and has an excellent slow-release effect. Figure 4 The cross-sectional view (above) and nitrogen distribution (below) of slow-release fertilizer impregnated with oil-tea camellia shell in Example 2 are shown. Figure 4 It can be seen that after the slow-release fertilizer based on the oil-tea camellia shell is impregnated, the thick-walled cells still retain a large amount of nitrogen, while the thin-walled cell cavity and cell wall contain almost no nitrogen. The thick-walled cells and thin-walled cells of the oil-tea camellia shell use their structural differences to release nutrients in a differentiated time, realizing intelligent controlled release of nutrients.

[0047] Figure 5 This is the crop growth situation in Example 2, Figure 6 This is the three-dimensional fluorescence spectrum of soil dissolved organic matter in Example 2. Figure 7 This is the percentage of each component of soil dissolved organic matter in Example 2. Figure 5 , Figure 6 and Figure 7 It can be seen that the use of the camellia husk-based organic and inorganic nutrient slow-release compound fertilizer for crop cultivation can effectively increase corn stem length and increase humic acid substances in the soil's dissolved organic matter. The above data proves that the camellia husk-based organic and inorganic nutrient slow-release compound fertilizer prepared using the camellia husk cell structure of the present invention can provide nutrients to crops and improve soil organic matter.

[0048] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A tea oil shell-based organic and inorganic nutrient slow-release compound fertilizer, characterized in that: The preparation method comprises the following steps: 1) Cleaning the oil-pressing waste from camellia seeds to remove non-camellia shell debris and obtain camellia shell raw materials; 2) crushing and drying the camellia oleifera shell raw material to obtain the shell substrate; 3) The fruit shell substrate is fully immersed in molten urea, and then filtered and cooled to obtain a camellia oleifera fruit shell-based organic and inorganic nutrient slow-release compound fertilizer.

2. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1, characterized in that: The oil-tea camellia shell raw material is crushed to a particle size of 0.2 cm to 1.5 cm.

3. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1, characterized in that: The fruit shell substrate is heated to 120° C. to 180° C. and then mixed with molten urea for impregnation.

4. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 3, characterized in that: The heating time of the fruit shell substrate is 0.5 h to 3 h.

5. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1, characterized in that: The immersion time is 0.2 h to 2 h.

6. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1 or 5, characterized in that: The immersion temperature is 135°C to 170°C.

7. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1, characterized in that: The drying temperature of camellia oleifera shell raw materials is 60 ℃ ~ 120 ℃.

8. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to claim 1 or 7, characterized in that: The drying time of camellia oleifera shell raw materials is 12 h to 48 h.

9. The oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to any one of claims 1 to 5 and 7, characterized in that: The mass mixing ratio of the fruit shell base material to the molten urea is 1: (1-6).

10. Use of the oil-tea camellia shell-based organic and inorganic nutrient slow-release compound fertilizer according to any one of claims 1 to 9 in soil improvement.

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