Rare earth cerium compound fertilizer and application thereof in saline alkali soil improvement

Abstract

The invention discloses a rare earth cerium compound fertilizer and application thereof in saline alkali soil improvement, and relates to the technical field of soil amendments, the rare earth cerium compound fertilizer comprises the following components by mass: 5-15 parts of cerium nitrate, 10-20 parts of glycine, 20-30 parts of mineral source potassium fulvate, 10-20 parts of pyroligneous liquor, and 25-35 parts of potassium dihydrogen phosphate; according to the rare earth cerium compound fertilizer provided by the invention, the cerium nitrate, the glycine, the mineral source potassium fulvate, the wood vinegar and the monopotassium phosphate are scientifically proportioned, so that the pH value of saline-alkali soil can be remarkably reduced, the content of heavy metals is reduced, and meanwhile, the content of nutrients such as nitrogen, phosphorus and potassium in the soil is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioners, and specifically to a rare earth cerium compound fertilizer and its application in saline-alkali soil improvement. Background Art

[0002] Saline soil and alkaline soil are collectively referred to as saline-alkali soil or saline soil, including primary saline-alkali soil and secondary saline-alkali soil. Saline soil refers to a general term for various types of soil in which there are high concentrations of soluble salt ions, which have an adverse impact on the physical, chemical, biological and other properties of the soil and plant growth, including salinized soil, alkalized soil, saline soil and alkaline soil, etc. Currently, the degree of soil salinization globally is still on the rise. The total area of saline soil in the world is about 1.1×109 hm 2 , of which 14% is defined as unsuitable for production, including forest land, wetland and nature reserve. It is estimated that the remaining 86% of saline soil provides 11% of the current global biomass production.

[0003] In saline-alkali soil dominated by Na+ and Cl-, a layer of white salt crust will appear on the soil surface in spring, with thick and compact particles, which is very obvious in temperate regions. The particle structure and porosity of the soil are also changing. With the increase in particle density, the soil is more likely to become compacted, the soil porosity decreases, resulting in a reduction in the water permeability and air permeability of the soil, and an increased possibility of surface runoff and soil erosion. The chemical properties of the soil are also changing. The ion concentration in the soil solution increases, the pH value rises, the electrical conductivity increases, the mineralization degrees of carbon and nitrogen decrease, and the enzyme activity in the soil is also inhibited, thus affecting the activities of soil microorganisms and the transformation of organic matter, and reducing the soil nutrient utilization rate, organic matter content and soil fertility. In some areas, phenomena such as land subsidence and salt swelling occur, which will not only have an adverse impact on engineering construction, but also make industrial land unable to be effectively utilized, causing huge economic losses. The high-salt and high-alkali environment will also accelerate the corrosion and damage of engineering facilities. Under the action of high-concentration salts, the formation of starch in the guard cells of stomata is hindered, the stomata cannot close, and the plants are prone to wither. Soil salinization will also affect the yield and quality of crops. The high-concentration salt environment will increase the osmotic pressure of the soil solution, thereby causing physiological drought in plants. In severe cases, water will exude from the root cells, resulting in the withering or even death of the plants. Due to the competition of Na+, the absorption of potassium, phosphorus and other nutrients by plants decreases, and the transfer of phosphorus is inhibited, affecting the nutritional status of plants, and further inhibiting the normal vegetative growth and reproduction of plants.

[0004] The main principle of the upper-covering and lower-separating salt-blocking technology is to reduce the evaporation of water on the ground surface, inhibit the salt-returning effect, set up a material addition layer in the soil layer to block the capillary siphon effect of the soil, and reduce the upward movement of deep-layer salts. Common methods include using straw materials, green manure plants, films, etc. to be used alone or in combination and optimized during agricultural production. This not only has a heat preservation effect on crops in the early growth stage of crops, but also does not affect water control and salt reduction in the later growth stage of crops, and has a good treatment and restoration effect on slightly saline-alkali land. For example, Lu Chuang et al. used straw interlayers to reduce soil salt content by 18.9% and 13.9%, increase the number of soil microbial populations, and increase the yield of sunflowers. High cost: It is necessary to use materials such as straw, green manure plants or films, and may need to be replaced regularly, increasing the treatment cost. The treatment effect of this technology on severely saline-alkali land may not be ideal and needs to be combined with other technologies. If the material selection is improper or the laying method is unreasonable, it may affect the growth and development of crops.

[0005] The subsurface pipe drainage and desalinization technology enhances the water storage capacity of farmland soil by laying subsurface pipe drainage equipment, thereby suppressing the return of soil salts to the surface layer. During irrigation, subsurface pipes can be used to accelerate the drainage efficiency, achieve the effect of flowing water leaching, and achieve the purpose of desalination and dealkalization. For example, Li Jingnan et al. used the subsurface pipe drainage and leaching effect, and the subsurface pipe desalination rate reached 81.79%-52.28%, and significantly increased the soil nutrient content and permeability. This technology requires the laying of subsurface pipe drainage equipment, with high construction difficulty and high cost. Moreover, the subsurface pipes are prone to blockage or damage and need regular maintenance and cleaning, increasing the management cost. Laying subsurface pipes may damage the natural structure of the soil and affect the air permeability and water permeability of the soil.

[0006] Water-saving irrigation achieves the effect of controlling soil salinity. The main technology is to use drip irrigation under plastic film technology for water-saving and salt control, optimize water allocation, improve rainwater utilization, improve irrigation water quality, furrow irrigation for salt inhibition, and saline water freezing and thawing and other irrigation methods for soil salinity control, and combine with water and fertilizer integrated management technology. The specific steps can be divided into: collecting and concentrating rainwater to strengthen the leaching and desalination of the soil; opening ditches for irrigation and drainage to remove the salinity at the roots of crops; drip irrigation under plastic film to leach the salts at the roots; freezing and thawing irrigation to use the salt-pressing effect of saline water freezing to achieve the purpose of reducing salinity. Through this series of measures, the high soil salinity problem in the northwest can be effectively reduced. This technology requires the construction of a drip irrigation system under plastic film or a rainwater collection system, with a large initial investment, requires precise control of irrigation water volume and irrigation time, and has high requirements for technology and management level. In arid areas, the water source may be insufficient, restricting the application of water-saving irrigation technology.

[0007] There are many plants with good salt tolerance on the market now. Agricultural planting can be carried out by screening and cultivating salt-tolerant crops or halophytic cash crops. The plant Atriplex can accumulate 300 kg of Cl− per hectare in one growing season, effectively reducing soil salinity. In addition to plants with good salt tolerance, soil microorganisms also play a huge role in the remediation of saline-alkali soil. Using salt-tolerant microorganisms and biological agents can improve the biological activity of the soil and the soil nutrient status, enhance the stress resistance of plants to salinity and alkalinity, and ultimately achieve the in-situ remediation ability of saline-alkali soil. At present, there are relatively few varieties of salt-tolerant crops in this technology, and the yields and qualities of some varieties may be inferior to those of conventional crops. Moreover, cultivating new varieties of salt-tolerant crops requires a long time and a large amount of manpower, material resources and financial resources.

[0008] Slope making and drainage is a fresh water flushing salt technology, which is mainly applicable to areas with relatively high terrain and good drainage performance. First, level the saline-alkali land and leave an appropriate slope, and dig drainage ditches at appropriate positions (usually dug on the green land), and then introduce water for irrigation. Dilute the soil salinity by flushing the saline-alkali land. The infiltration of water can discharge the dissolved salts and alkalis into the drainage ditches; finally, drain the water containing salts and alkalis. This technology is mainly applicable to areas with relatively high terrain and good drainage performance, and has poor effects on areas with low-lying terrain or poor drainage. Summary of the Invention

[0009] To solve the above technical problems, the present invention provides a rare earth cerium compound fertilizer, which is composed of the following components: cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, potassium dihydrogen phosphate; By mass ratio, cerium nitrate is 5 parts - 15 parts, glycine is 10 parts - 20 parts, mineral source fulvic acid potassium is 20 parts - 30 parts, wood vinegar liquid is 10 parts - 20 parts, and potassium dihydrogen phosphate is 25 parts - 35 parts.

[0010] Moreover, the purity of the cerium nitrate ≥ 99.9%, the purity of the mineral source fulvic acid potassium ≥ 75%, and the organic acid content of the wood vinegar liquid ≥ 99%.

[0011] Moreover, the preparation method of the rare earth cerium compound fertilizer is as follows: (1) Dissolve cerium nitrate in deionized water and stir until completely dissolved to obtain a cerium nitrate solution; (2) Add glycine to the cerium nitrate solution and stir and react for 30 - 60 minutes to form a rare earth - amino acid complex; (3) Add mineral source fulvic acid potassium, wood vinegar liquid and potassium dihydrogen phosphate in sequence, stir and mix evenly to obtain a composite rare earth cerium fertilizer.

[0012] On the other hand, the present invention provides an application of a rare earth cerium compound fertilizer in the improvement of saline-alkali soil, which is used to reduce the soil pH value, reduce the heavy metal content, increase the content of nitrogen, phosphorus and potassium nutrients in the soil, increase the soil porosity, improve the water and fertilizer retention capacity of the soil, promote the development of plant roots and the synthesis of chlorophyll.

[0013] The application method is as follows: the rare earth cerium compound fertilizer is applied in pot culture at a dosage of 3 - 4 ml per 140 g of saline-alkali soil, and the application period is once every 3 days.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The rare earth cerium compound fertilizer provided by the present invention can significantly reduce the pH value of saline-alkali soil, reduce the heavy metal content, and at the same time increase the content of nutrients such as nitrogen, phosphorus and potassium in the soil by scientifically proportioning cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid and potassium dihydrogen phosphate; at the same time, this compound fertilizer can increase the soil porosity, improve the water and fertilizer retention capacity of the soil, improve the physical structure of the soil, make the soil more loose and porous, which is beneficial to the development of plant roots and the absorption of nutrients. This improvement effect helps to enhance the overall function of the soil and promote the healthy growth of plants.

[0015] 2. The rare earth elements and amino acids in the rare earth cerium compound fertilizer provided by the present invention can act synergistically to promote the development of plant roots and the synthesis of chlorophyll, improve the photosynthesis efficiency of plants, and thus enhance the growth potential and stress resistance of plants. This is particularly important for plants growing in saline-alkali environments, and can significantly improve their survival rate and yield.

[0016] 3. Compared with traditional chemical modifiers, the rare earth cerium compound fertilizer provided by the present invention is more environmentally friendly and will not cause secondary pollution to the soil and the environment. At the same time, by improving the soil structure and soil fertility, it helps to achieve the sustainable development of agriculture and reduce the dependence on chemical fertilizers and pesticides. Description of the Drawings

[0017] Figure 1 For soil-cultivated plants with different amounts of rare earth cerium from 1 - 5 ml; Figure 2 For the comparison chart of crops with different rare earth cerium nitrate compound fertilizers; Figure 3 For the comparison chart of the growth of plants with cerium nitrate compound fertilizer; Figure 4 For the comparison chart of soil organic matter; Figure 5 For the comparison chart of soil ammonium nitrogen; Figure 6 For the comparison chart of soil available phosphorus; Figure 7 For the comparison chart of soil available potassium; Figure 8It is a comparison chart of heavy metals in different soils; Figure 9 SEM images of different soils; Figure 10 It is the energy spectrum diagram of blank soil; Figure 11 It is the energy spectrum diagram of the upper layer soil of cerium nitrate compound fertilizer; Figure 12 It is the energy spectrum diagram of the middle layer soil of cerium nitrate compound fertilizer; Figure 13 It is the energy spectrum diagram of the lower layer soil of cerium nitrate compound fertilizer; Figure 14 It is a comparison chart of adsorption and desorption of different soils; Figure 15 It is a comparison chart of the average distribution of different soils; Figure 16 It is the Fourier infrared diagram of different soils; Figure 17 It is the Raman spectrum diagram of different soils; Figure 18 It is the XRD diagram of cerium nitrate compound fertilizer. Specific implementation mode

[0018] Example 1 A rare earth cerium compound fertilizer, the rare earth cerium compound fertilizer is composed of the following components: cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, potassium dihydrogen phosphate; According to the mass ratio, 5 parts of cerium nitrate, 10 parts of glycine, 20 parts of mineral source fulvic acid potassium, 10 parts of wood vinegar liquid, and 25 parts of potassium dihydrogen phosphate.

[0019] Moreover, the purity of the cerium nitrate ≥ 99.9%, the purity of the mineral source fulvic acid potassium ≥ 75%, and the organic acid content of the wood vinegar liquid ≥ 99%.

[0020] Furthermore, the preparation method of the rare earth cerium compound fertilizer is as follows: (1) Dissolve cerium nitrate in deionized water and stir until completely dissolved to obtain a cerium nitrate solution; (2) Add glycine to the cerium nitrate solution and stir and react for 30 minutes to form a rare earth - amino acid complex; (3) Add mineral source fulvic acid potassium, wood vinegar liquid and potassium dihydrogen phosphate in sequence, stir and mix evenly to obtain a composite rare earth cerium fertilizer.

[0021] Example 2 A rare earth cerium compound fertilizer, the rare earth cerium compound fertilizer is composed of the following components: cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, potassium dihydrogen phosphate; According to the mass ratio, 15 parts of cerium nitrate, 20 parts of glycine, 30 parts of mineral source fulvic acid potassium, 20 parts of wood vinegar liquid, and 35 parts of potassium dihydrogen phosphate.

[0022] Moreover, the purity of the cerium nitrate ≥ 99.9%, the purity of the potassium fulvate from mineral source ≥ 75%, and the organic acid content of the wood vinegar liquid ≥ 99%.

[0023] Furthermore, the preparation method of the rare earth cerium compound fertilizer is as follows: (1) Dissolve cerium nitrate in deionized water and stir until completely dissolved to obtain a cerium nitrate solution; (2) Add glycine to the cerium nitrate solution and stir and react for 60 minutes to form a rare earth - amino acid complex; (3) Sequentially add potassium fulvate from mineral source, wood vinegar liquid and potassium dihydrogen phosphate, stir and mix evenly to obtain the compound rare earth cerium fertilizer.

[0024] Example 3 A rare earth cerium compound fertilizer, which is composed of the following components: cerium nitrate, glycine, potassium fulvate from mineral source, wood vinegar liquid, potassium dihydrogen phosphate; By mass ratio, 10 parts of cerium nitrate, 15 parts of glycine, 25 parts of potassium fulvate from mineral source, 15 parts of wood vinegar liquid, and 30 parts of potassium dihydrogen phosphate.

[0025] Moreover, the purity of the cerium nitrate ≥ 99.9%, the purity of the potassium fulvate from mineral source ≥ 75%, and the organic acid content of the wood vinegar liquid ≥ 99%.

[0026] Furthermore, the preparation method of the rare earth cerium compound fertilizer is as follows: (1) Dissolve cerium nitrate in deionized water and stir until completely dissolved to obtain a cerium nitrate solution; (2) Add glycine to the cerium nitrate solution and stir and react for 45 minutes to form a rare earth - amino acid complex; (3) Sequentially add potassium fulvate from mineral source, wood vinegar liquid and potassium dihydrogen phosphate, stir and mix evenly to obtain the compound rare earth cerium fertilizer.

[0027] Example 4 Application of the rare earth cerium compound fertilizer described in Example 3 in improving saline - alkali soil. The rare earth cerium fertilizer is used to reduce the soil pH value, reduce the heavy metal content, increase the content of soil nitrogen, phosphorus and potassium nutrients, increase the soil porosity, enhance the soil water - retaining and fertilizer - retaining capacity, promote plant root development and chlorophyll synthesis.

[0028] The application method is: apply the rare earth cerium compound fertilizer to potted plants at a dosage of 3 ml per 140 g of saline - alkali soil, and the application period is once every 3 days.

[0029] Experimental part 1. Experimental materials Table 1 Experimental reagents

[0030] 2. Experimental equipment (1) Electric blast drying oven (Model DHG-9000B, Beijing Aerospace Keyu Testing Instrument Co., Ltd.) (2) Electronic balance (Model JJ124BC, China Instrument City Co., Ltd.) (3) Magnetic heating stirrer (Model HJ-6B Jintan Experimental Instrument Co., Ltd.): used to stir chemical reagents evenly and maintain the uniformity of the solution.

[0031] (4) pH / conductivity tester (Model PHSJ-6L, Shanghai Yidian Leici Co., Ltd.; Leici DDS-307A, Muyuan Shanghai Environmental Protection Technology Co., Ltd.) (5) Agate mortar (Model HW-3, manufactured by Tianjin Hengchuang Da Technology Development Co., Ltd.) (6) Scanning electron microscope (SEM) (model GAIA 3XMN, Czech Republic, Tesken) (7) Fourier transform infrared spectrometer (model TENSOR II, Bruker, Germany) (8) Raman spectrometer (Model: Dimensionlcon, Bruker, Germany) (9) X-ray diffractometer (Model: D8ADVANCE, Bruker, Germany) (10) X-ray photoelectron spectrometer (ESCALAB 250Xi, Thermo Fisher Scientific) (11) X-ray fluorescence spectrometer (model EDX6000C, Tianrui Instrument Co., Ltd.) (12) Specific surface area instrument (Model ASAP2460, brand Micromeritics) (13) Chlorophyll meter (Model TYS-4N, Mince Instruments) (14) Soil nutrient detector (Model LD-GT3, Lainder)

[0032] Experiment 1 1. Selection of rare earth species: Cerium nitrate, cerium oxide, and cerium nitrate + glycine were selected to plant alfalfa. After one week, the growth of the crops was observed to determine which cerium fertilizer was the best for the experiment. Figure 1For soil-cultivated plants with different amounts of rare earth cerium (1 - 5 ml), in the figure: 1 is the blank control, 2, 3, and 4 are plants with 0.075 g, 0.1 g, and 0.125 g of pure cerium oxide added (at the same concentration as other rare earth cerium), 5, 6, and 7 are plants with 1 ml, 3 ml, and 5 ml of cerium nitrate added, and 8, 9, and 10 are plants with 1 ml, 3 ml, and 5 ml of cerium nitrate and glycine added. It can be seen from the figure that the growth of plants with cerium oxide added is better than that of the blank plants, and the 0.1 g plant has the best effect. Compared with cerium nitrate, the growth of plants with cerium nitrate is better than that of plants with cerium oxide, and among them, the growth of plants with 3 ml of cerium nitrate added is the best. When comparing plants with cerium nitrate and plants with cerium nitrate plus glycine, the growth of plants with cerium nitrate is lower than that of plants with glycine added. Therefore, it can be concluded that the growth state of plants with cerium nitrate + glycine added is significantly better than that of other plants with pure cerium oxide and pure cerium nitrate added. So, cerium nitrate + glycine is selected as the test material in the following experiments.

[0033] Confirm that cerium nitrate + glycine is used as the base. To confirm that the addition of other materials can maximize the fertilizer effect, three kinds of rare earth cerium nitrate compound fertilizers are made for planting to determine the compound fertilizer with the best fertilizer effect. Observe the growth status of the crops after one week and select the appropriate compound fertilizer. Figure 2 For the comparison chart of crops with different rare earth cerium nitrate compound fertilizers: 1 is the blank control, 2, 3, and 4 are plants with 1 ml, 3 ml, and 5 ml of cerium nitrate compound fertilizers containing cerium nitrate, glycine, humic acid, and potassium dihydrogen phosphate, 5, 6, and 7 are plants with 1 ml, 3 ml, and 5 ml of cerium nitrate compound fertilizers containing cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate, and 8, 9, and 10 are plants with 1 ml, 3 ml, and 5 ml of cerium nitrate compound fertilizers with the compound of cerium nitrate and lanthanum nitrate plus glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate. According to Figure 2 It can be seen that the growth of cerium nitrate compound fertilizers containing cerium nitrate, glycine, humic acid, and potassium dihydrogen phosphate is better than that of the blank plants, and the 5 ml compound fertilizer plant has the best effect. When comparing the cerium nitrate compound fertilizers containing cerium nitrate, glycine, humic acid, and potassium dihydrogen phosphate with the cerium nitrate compound fertilizers containing cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate, the growth of compound fertilizers with wood vinegar liquid and mineral source fulvic acid potassium added is better than that of compound fertilizers with humic acid, and the 3 ml has the best growth. When comparing the cerium nitrate compound fertilizers with the compound of cerium nitrate and lanthanum nitrate plus glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate with the cerium nitrate compound fertilizers containing cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate, its growth is slightly weaker than that of pure cerium nitrate and wood vinegar liquid plants. Therefore, it can be concluded that the growth state of plants with cerium nitrate compound fertilizers containing cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate is significantly better than that of other cerium nitrate compound fertilizers. So, cerium nitrate compound fertilizers containing cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate are selected as the test material in the following experiments.

[0034] Experiment 2 2.1 Single-factor experiment Select 140 g of saline-alkali soil quality, apply the cerium nitrate compound fertilizer prepared in Example 3 of the present invention, and determine the application concentration for a single-factor experiment, which are 3 ml, 4 ml, 5 ml, 6 ml, and 7 ml respectively. At the same time, conduct a single-factor experiment on the application time of various fertilizers, which are fertilizing every three days and applying cerium fertilizer every four days, to determine the best conditions for plant growth, and make an optimal compound fertilizer improvement plan. Figure 3 It is a comparison chart of the growth of plants with cerium nitrate compound fertilizer. In the figure, No. 1 is blank soil cultivation, No. 2-6 are cerium fertilizers applied every three days at 3 ml-7 ml, No. 7-11 are fertilizers applied every four days at 3 ml-7 ml. Observe the effects after two weeks of planting. It can be seen from the figure that the soil cultivation effect of applying cerium nitrate compound fertilizer is greater than that of blank soil cultivation. Among them, the growth trend of fertilizing every three days is significantly better than that of fertilizing every four days. From the planting effects of different concentrations of soil cultivation with fertilization every three days, the growth trend of soil cultivation with 4 ml of cerium nitrate compound fertilizer (No. 3) is the best.

[0035] 2.2 Analysis of roots, stems and leaves under different planting conditions Measure four plants in the same pot and take the average value. No. 0 is the blank plant, No. 1-5 are plants cultivated in soil with different concentrations of 3-7 ml of rare earth cerium nitrate + glycine, No. 6-10 are plants cultivated in soil with different concentrations of 3-7 ml of rare earth cerium nitrate, No. 11-15 are plants cultivated in soil with different concentrations of 3-7 ml of wood vinegar + mineral source fulvic acid + potassium dihydrogen phosphate, and No. 16-20 are plants cultivated in soil with different concentrations of 3-7 ml of rare earth lanthanum nitrate compound fertilizer. The stem lengths are shown in Table 2, the root lengths are shown in Table 3, and the leaf lengths are shown in Table 4. It can be seen from Tables 2-4 that the average stem length of applying 4 ml of cerium nitrate compound fertilizer is the longest (No. 17), the average root length of adding 5 ml of rare earth lanthanum nitrate and glycine is the longest (No. 3), and the leaf length of applying 4 ml of rare earth cerium nitrate compound fertilizer is the longest (No. 17).

[0036] Table 2 Stem length (cm)

[0037] Table 3 Root length (cm)

[0038] Table 4 Leaf length (cm)

[0039] 2.3 Conductivity / pH analysis under different planting conditions (1)Conductivity (us / cm) Plant No. 0 is the blank plant, Plants No. 1 - 5 are soil - cultivated plants with different concentrations of cerium nitrate rare - earth + glycine at 3 - 7 ml, Plants No. 6 - 10 are soil - cultivated plants with different concentrations of cerium nitrate rare - earth at 3 - 7 ml, Plants No. 11 - 15 are soil - cultivated plants with different concentrations of wood vinegar liquid + mineral - source fulvic acid + potassium dihydrogen phosphate at 3 - 7 ml, and Plants No. 16 - 20 are soil - cultivated plants with different concentrations of lanthanum nitrate rare - earth compound fertilizer at 3 - 7 ml. Table 5 shows the conductivity results. It can be seen from the table that the conductivity of the cerium nitrate rare - earth compound fertilizer at 4 ml is the lowest (Plant No. 17).

[0040] Table 5 Conductivity (us / cm)

[0041] (2)pH Plant No. 0 is the blank plant, Plants No. 1 - 5 are soil - cultivated plants with different concentrations of cerium nitrate rare - earth + glycine at 3 - 7 ml, Plants No. 6 - 10 are soil - cultivated plants with different concentrations of cerium nitrate rare - earth at 3 - 7 ml, Plants No. 11 - 15 are soil - cultivated plants with different concentrations of wood vinegar liquid + mineral - source fulvic acid + potassium dihydrogen phosphate at 3 - 7 ml, and Plants No. 16 - 20 are soil - cultivated plants with different concentrations of lanthanum nitrate rare - earth compound fertilizer at 3 - 7 ml. The results are shown in Table 6. It can be seen from the table that when the concentration of lanthanum nitrate rare - earth compound fertilizer is 3 - 7 ml, the pH is close to neutral and the improvement effect is the best (Plants No. 16 - 20), and when the concentration of cerium nitrate rare - earth compound fertilizer is 4 ml, it is the closest to neutral.

[0042] Table 6 pH

[0043] 2.4 Analysis of different soil organic matters Sample No. 1 is the blank soil. Samples No. 2 and 3 are the soils with the best - growing plants of cerium nitrate at concentrations of 3 ml and 4 ml respectively. Samples No. 4 and 5 are the soils with the best - growing plants of cerium nitrate + glycine at concentrations of 3 ml and 5 ml respectively. Samples No. 6 and 7 are the soils with the best - growing plants of wood vinegar liquid + mineral - source fulvic acid + potassium dihydrogen phosphate at concentrations of 3 ml and 4 ml respectively. Samples No. 8 and 9 are the soils with the best - growing plants of cerium nitrate compound fertilizer at concentrations of 3 ml and 4 ml respectively. Figure 4 The following is a comparison chart of soil organic matter: The soil organic matter of the soil applied with mineral - source fulvic acid, wood vinegar liquid, and potassium dihydrogen phosphate fertilizer is higher than that of the blank soil. The soil organic matter of the cerium nitrate compound fertilizer with added cerium nitrate and glycine is much higher than that of the soil applied with mineral - source fulvic acid, wood vinegar liquid, and potassium dihydrogen phosphate fertilizer. Therefore, it can be concluded that the effect of the cerium nitrate compound fertilizer is much greater than that of others. Among them, the soil organic matter of the cerium nitrate compound fertilizer at 3 ml is the most.

[0044] 2.5 Analysis of different soil nitrogen, phosphorus, and potassium 1. Soil ammonium nitrogen Sample No. 1 is blank soil, Sample No. 2 is the soil with the best growth of cerium nitrate, Sample No. 3 is the soil with the best growth of cerium nitrate plus glycine, Sample No. 4 is the soil with the best growth of mineral-source fulvic acid potassium + wood vinegar liquid + potassium dihydrogen phosphate, and Samples No. 5, 6, and 7 are the soils with different concentrations of 3 ml, 4 ml, and 7 ml of the plants with better growth under the application of cerium nitrate compound fertilizer. Figure 5 It is the comparison chart of soil ammonium nitrogen: The ammonium nitrogen content of Sample No. 1 blank soil is relatively low, and the ammonium nitrogen contents of Samples No. 2 - 7 are relatively high. Among them, the ammonium nitrogen content of the soil applied with 3 ml of cerium nitrate compound fertilizer is lower than that of the soil applied with mineral-source fulvic acid potassium + wood vinegar liquid + potassium dihydrogen phosphate fertilizer, which may be due to the relatively low application concentration resulting in the incomplete release of the effects of rare earth amino acids. Rare earth + glycine promotes the release of ammonium nitrogen in potassium dihydrogen phosphate + mineral-source fulvic acid potassium + wood vinegar liquid. Among them, the effect of 4 ml of cerium nitrate compound fertilizer is the best. In saline-alkali soil, the low concentration of ammonium nitrogen will inhibit the photosynthesis and respiration of plants, reduce the synthesis amount of chlorophyll, and the leaves will turn yellow, affecting the growth of plants. Appropriately applying cerium nitrate compound fertilizer will increase the soil ammonium nitrogen content, ensure the normal photosynthesis demand of plants, regulate the growth and development of plants, and improve the stress resistance of plants.

[0045] 2. Soil available phosphorus Sample No. 1 is blank soil, Sample No. 2 is the soil with the best growth of cerium nitrate, Sample No. 3 is the soil with the best growth of cerium nitrate plus glycine, Sample No. 4 is the soil with the best growth of mineral-source fulvic acid potassium + wood vinegar liquid + potassium dihydrogen phosphate, and Samples No. 5, 6, and 7 are the soils with different concentrations of 3 ml, 4 ml, and 7 ml of the plants with better growth under the application of cerium nitrate compound fertilizer. Figure 6 It is the comparison chart of soil available phosphorus: The available phosphorus content of Sample No. 1 blank soil is relatively high, and the available phosphorus contents of Samples No. 2, 3, and 5 are relatively low, indicating the relative lack of available phosphorus in these soils. The available phosphorus contents of Samples No. 4, 6, and 7 are relatively high, and all are higher than the available phosphorus content of the blank soil, indicating that the available phosphorus in these soils is relatively abundant. Among them, the effect of applying 4 ml of cerium nitrate compound fertilizer is the best. Applying cerium nitrate compound fertilizer will increase the available phosphorus content, convert insoluble phosphates into available phosphorus, enable plants to grow and develop better, make the roots strong, and enable them to better absorb water and nutrients in the soil.

[0046] 3. Soil available potassium Sample No. 1 is blank soil, Sample No. 2 is the soil with the best growth of cerium nitrate, Sample No. 3 is the soil with the best growth of cerium nitrate plus glycine, Sample No. 4 is the soil with the best growth of mineral-source fulvic acid potassium + wood vinegar liquid + potassium dihydrogen phosphate, and Samples No. 5, 6, and 7 are the soils with different concentrations of 3 ml, 4 ml, and 7 ml of the plants with better growth under the application of cerium nitrate compound fertilizer. Figure 7It is a comparative graph of available potassium in soil: For samples 1 - 3, the content is relatively low, indicating that the available potassium in these soils is relatively scarce. For samples 4 - 7, the content is relatively high, suggesting that the available potassium in these soils is relatively abundant. Among them, the 4 - ml cerium nitrate compound fertilizer shows the best effect. The low content of available potassium in saline - alkali soil will reduce the stress resistance of plants. When the available potassium is low, a large number of necrotic spots will appear on the edges of plant leaves, affecting the water - regulating ability of the leaves. Applying cerium nitrate compound fertilizer will increase the content of available potassium in the soil. A high content of available potassium can maintain the osmotic pressure inside plant cells and promote the water absorption ability.

[0047] 2.6 Analysis of heavy metals in different soils Sample 1 is blank soil, sample 2 is the soil with the best growth situation under cerium nitrate planting, sample 3 is the soil with the best growth situation under cerium nitrate plus glycine planting, sample 4 is the soil with the best growth situation under mineral - sourced fulvic acid + wood vinegar + potassium dihydrogen phosphate planting, and sample 5 is the soil with the best growth situation under cerium nitrate compound fertilizer planting. Figure 8 It is a comparative graph of heavy metals in different soils: After applying cerium nitrate compound fertilizer, the heavy metals mercury and nickel in the soil are significantly reduced. The excessive heavy metal content in saline - alkali soil leads to hindered growth and development. Reducing soil fertility and sustainable utilization rate will have a toxic effect on plants, changing physiological characteristics such as plant height, main root length, and leaf area, resulting in weak root absorption and even plant death. Applying cerium nitrate compound fertilizer will reduce the heavy metal content in the soil, reducing the amount of heavy metals absorbed by plants, avoiding the damage of heavy metals to plant cells, enabling plants to better absorb nutrients in the soil such as nitrogen, phosphorus, and potassium, enhancing stress resistance, and promoting normal plant development.

[0048] 2.7 Chlorophyll analysis Sample 1 is a blank soil - cultivated plant, sample 2 is the soil - cultivated plant with the best growth situation under cerium nitrate planting. Sample 3 is the soil - cultivated plant with the best growth situation under cerium nitrate plus glycine planting, sample 4 is the soil - cultivated plant with the best growth situation under mineral - sourced fulvic acid + wood vinegar + potassium dihydrogen phosphate planting, and sample 5 is the soil - cultivated plant with the best growth situation under cerium nitrate compound fertilizer planting. In this experiment, the second - tallest plant leaves in each soil - cultivation were measured. Table 7 shows the chlorophyll content results: The chlorophyll content of the soil - cultivated plants applying cerium nitrate compound fertilizer is 32.6, higher than that of the blank soil - cultivated plants, with a 40.5% increase. Applying cerium nitrate compound fertilizer is also higher than that of the plants only applying mineral - sourced fulvic acid + wood vinegar + potassium dihydrogen phosphate, with a 14.4% increase. It can be seen that rare - earth cerium plus glycine promotes the absorption of other substances by plants.

[0049] Table 7 Chlorophyll content

[0050] Experiment 3

[0051] 3.1 Soil scanning electron microscopy analysis The scanning electron microscope (SEM) is a large-scale analytical instrument that uses an electron beam to scan the surface of a sample and obtains information on the surface morphology and composition of the sample by collecting secondary electron signals, etc. In this experiment, the SEM was used to observe the surface and internal structure of the soil applied with cerium nitrate compound fertilizer. Figure 9 SEM images of different soils.

[0052] Upper left image a: Particles of different sizes can be seen on the soil surface. The large particles may be sand grains or silt grains, and the small particles may be clay particles. The particle shapes are irregular, reflecting the morphology of soil particles after weathering, erosion and other effects in the natural environment. There are pores between the particles, which are the basis for soil aeration and water permeability. The pore sizes and shapes vary. The large pores are conducive to air circulation and rapid water infiltration, while the small pores help to retain water and nutrients. The surface of the soil particles is uneven, with protrusions, depressions and attached tiny particles, which may be clay minerals, organic matter or iron and aluminum oxides, etc. These substances will affect the adsorption, fertilizer retention and other properties of the soil.

[0053] Upper right image b: The soil particles have diverse and irregular shapes, with obvious size differences. Compared with the blank soil, there seems to be some substances attached or wrapped on the surface of some particles. It may be that after the action of cerium nitrate compound fertilizer, the components contained in it (such as cerium element-related compounds, etc.) undergo adsorption, precipitation and other reactions on the soil particle surface. The pore shapes and sizes are complex, with both large pores and small pores. The large pores may be formed during the rearrangement or dissolution-precipitation process of soil particles due to the influence of the compound fertilizer; the small pores may be related to soil colloid aggregation, compound filling, etc. The change of pore structure will affect the soil aeration, water permeability and water retention. The surface of the soil particles is uneven, with many protrusions, depressions and gaps, which may be caused by the chemical reaction between the ions in the compound fertilizer and the soil particles, or the activities of soil microorganisms and other factors. These microscopic changes may further affect the migration, transformation of nutrients in the soil and the absorption of nutrients by plant roots.

[0054] Lower left image c: The soil particles have irregular shapes and uneven size distributions. Compared with the blank soil, the edges of some particles seem to be more blurred. It may be that the components in the cerium nitrate compound fertilizer react in the middle layer of the soil, forming new substances wrapped on the particle surface, or particle aggregation occurs between the particles. The pore morphologies are diverse, with both relatively large pores and small pores. The large pores may be the spaces left after the dissolution or migration of some substances in the soil; the small pores may be caused by soil colloid aggregation, salt crystallization filling, etc. The change of pore structure will affect the soil aeration, water permeability and water retention. The surface of the soil particles is rough, with obvious protrusions, depressions and gullies, which may be due to the chemical reaction between the ions in the compound fertilizer and the soil particles, changing the texture of the particle surface, or the traces left by microbial activities or physical and chemical processes in the soil. These microscopic characteristics will affect the processes of nutrient adsorption, desorption and migration in the soil.

[0055] Lower right image d: Particle characteristics: The soil particles are irregular in shape and vary in size. Compared with the blank soil and the soil with cerium nitrate compound fertilizer applied at other layers, the particle aggregates may be different. Some particle surfaces appear relatively compact, possibly because the ions in the cerium nitrate compound fertilizer infiltrate downward with water and react in the lower soil layer, promoting enhanced interaction between particles and forming a relatively tight structure. The pore morphology and size are uneven. The number and distribution of large pores may differ from those of the soil at other layers. It may be that substances in the upper soil layer are leached to the lower layer with water, filling some pores, or it may be that the physical and chemical properties of the lower soil layer itself change under the action of the compound fertilizer, resulting in pore structure adjustment. The change in pore structure will affect the ventilation, water permeability, water retention, and fertilizer retention properties of the soil. There are certain undulations and irregularities on the soil particle surface, and there are some signs of tiny attachments or crystal depositions, which may be the result of precipitation, crystallization, and other reactions of certain components in the cerium nitrate compound fertilizer in the lower soil environment. These microscopic changes will affect nutrient transformation and microbial habitat in the soil.

[0056] Figure 10 This is the energy spectrum diagram of the blank soil. Figure 11 This is the energy spectrum diagram of the upper soil layer with cerium nitrate compound fertilizer. Figure 12 This is the energy spectrum diagram of the middle soil layer with cerium nitrate compound fertilizer. Figure 13 This is the energy spectrum diagram of the lower soil layer with cerium nitrate compound fertilizer. According to Figures 10 - 13As can be seen from the figure, the oxygen content in the blank soil is the highest, reaching 51.46% in mass fraction. The contents of Fe, C, Ca, and Si are relatively high. In the upper layer of the cerium nitrate compound fertilizer soil, the oxygen and carbon contents are significant, with the oxygen mass fraction being 56.16% and the carbon being 21.78%. Compared with the blank soil, the obvious increase in the carbon content may be due to the organic components in the compound fertilizer or fertilization promoting plant growth, and the return of plant residues increasing the organic carbon. The Ca content is 12.51%, higher than that in the blank soil, which may be due to the compound fertilizer containing Ca elements or changing the soil environment, resulting in changes in the existing form and content of Ca. The cerium element appears with a mass fraction of 0.01%, indicating that the cerium in the cerium nitrate compound fertilizer enters the upper layer of the soil. In the middle layer of the cerium nitrate compound fertilizer soil, the oxygen content is 49.92% and the carbon is 15.63%. Compared with the upper layer, the carbon content decreases, which may be due to the change in the degree of decomposition and input of organic carbon with increasing depth. The Si content is relatively high at 10.64%, the Fe content is 10.02%, and the Ce content is 7.00%. The relatively high Ce content in the middle layer may be related to the migration characteristics of elements in the soil after fertilization. The Ca content drops significantly to 1.02%, which may be caused by processes such as the migration, adsorption - desorption of elements in the soil profile. In the lower layer of the cerium nitrate compound fertilizer soil, the oxygen content is 48.87% and the carbon is 29.63%. The carbon content increases again, which may be because with increasing depth, the activities of soil microorganisms weaken, and the decomposition of organic carbon slows down and accumulates. The contents of elements such as Si, Ce, Ca, and Fe are different from those in the middle layer. The Si content is 6.27%, the Ce content is 5.61%, and the Ca content is 4.41%, reflecting the uneven migration and distribution of elements in the soil profile.

[0057] Applying the cerium nitrate compound fertilizer changes the elemental composition and distribution of the soil, especially the C and Ce elements. The changes in the elemental contents in different soil layers are different, indicating that the elements in the fertilizer have processes of migration and transformation in the soil and are affected by soil properties and microbial activities. The contents of elements such as Ca and Fe fluctuate in the soil profile, which may involve processes such as adsorption, desorption, precipitation, and dissolution. For example, the significant decrease in Ca in the middle layer of the soil may be due to chemical reactions with other components in the soil or downward migration. After adding the fertilizer, the carbon content in each layer of the soil changes significantly, which has important effects on soil fertility, structure, and microbial activities, etc. Calcium can increase the cation exchange capacity of the soil, reduce nutrient loss, and at the same time can also reduce the absorption of heavy metals by crops, improve the safety of agricultural products, and enhance the fertilizer - retaining capacity of the soil.

[0058] 3.2 Specific surface area and porosity (BET) analysis The BET specific surface area refers to the total surface area of a unit mass of solid material calculated through the Brunauer - Emmett - Teller (BET) theory, including the external surface and the internal surface. The BET theory is based on the multi - molecular layer adsorption model, assuming that the surface of the adsorbent is uniform and the adsorption process is dominated by physical adsorption. By measuring the adsorption amount of gas (usually nitrogen) on the solid surface and combining with the BET equation, the specific surface area of the material can be calculated.Figure 14 This is a comparison chart of adsorption and desorption of different soils. Unmodified curve: At the stage of relatively low relative pressure, the adsorption amount increases slowly. As the relative pressure increases, the adsorption amount gradually rises. When the relative pressure approaches 1, the adsorption amount increases sharply. This indicates that the adsorption capacity of the unmodified soil is limited at low pressure, and the adsorption amount increases significantly at high pressure. The overall trend of the modified curve is similar to that of the unmodified curve, but at the same relative pressure, the adsorption amount of the modified soil is generally higher than that of the unmodified soil. It is proved that after soil modification, the pore structure is improved, the specific surface area increases or the pore volume increases, enhancing the gas adsorption capacity.

[0059] Figure 15 This is a comparison chart of the average distribution of different soils. Fertilizer (black line): There are multiple peaks in the range of about 20 - 120 nm in pore diameter, indicating that the pores in this pore diameter range in this soil are relatively abundant, and the pore distribution of different pore diameters has a certain discreteness. Water (blank red line): The overall trend of the pore volume change is relatively flat, the peak is not as obvious as the fertilizer curve, and it is mainly concentrated in the smaller pore diameter area. It shows that compared with the soil treated with fertilizer, the pore diameter distribution of the soil under the action of water is relatively concentrated in the smaller pore diameter range, and the large pore diameter pores are relatively few. It shows that under the action of cerium nitrate compound fertilizer, the soil is improved and the pore structure is also improved.

[0060] 3.3 Fourier Transform Infrared Spectrometer Analysis A Fourier Transform Infrared Spectrometer (FT-IR) is a spectroscopic analysis instrument that uses Fourier transform technology to analyze infrared light to obtain information on the molecular structure of substances. It measures the infrared interference light passing through the sample, converts the interference signal in the time domain into an infrared spectrum in the frequency domain through Fourier transform, and then determines the functional groups and chemical bonds present in the sample based on different absorption peaks in the spectrum to achieve qualitative analysis of the sample. Quantitative analysis can also be carried out based on the absorption peak intensity. In this experiment, the vibration peaks of chemical bonds (such as C=O, C-H, O-H, etc.) in cerium nitrate compound fertilizer and the soil under the condition of this fertilizer are detected by infrared spectroscopy to determine the types and distribution states of functional groups in the material and verify the chemical modification effect of rare earth doping on the polymer matrix. Figure 16 This is the Fourier infrared diagram of different soils: The blank soil shows obvious characteristic peaks at 2981.4 cm -1 、2919.8 cm -1 、2351.1 cm -1 、1415.9 cm -1 、1037.7 cm -1 and 425.8 cm -1 There are obvious characteristic peaks. At 425.08 cm -1: This absorption peak may be related to the stretching vibrations of some metal oxides in the soil, such as Fe-O and Al-O. In the soil, metal oxides and hydroxides like iron and aluminum are relatively common, and this peak reflects the presence characteristics of such substances. 1037.7 cm -1 : Most likely corresponding to the Si-O-Si or Si-O-Al stretching vibrations of silicate minerals in the soil. Silicate minerals such as quartz and feldspar are widely present in the soil, and this peak is an important characterization of the silicate structure. 1415.9 cm -1 : It may be the absorption peak of organic functional groups in the soil (such as the antisymmetric stretching vibration of the carboxyl group -COO-) or carbonates (the antisymmetric stretching vibration of CO3 2- ). The organic matter and carbonate components in the soil will produce similar absorptions. 2351.1 cm -1 : It may be related to the absorption of carbon dioxide (CO2) in the air. During the testing process, if the instrument sealing and other conditions are not good, CO2 in the air will produce this absorption peak, and it may also be related to trace carbonates in the soil. 2919.8 cm -1 and 2981.4 cm -1 : Generally related to the C-H stretching vibrations of methyl (-CH3) and methylene (-CH2-) in organic matter. It indicates the presence of a certain amount of organic matter in the soil, and these organic functional groups play important roles in soil nutrient storage, structure stability, etc.

[0061] The cerium nitrate compound fertilizer soil showed obvious characteristic peaks at 445.6 cm -1 、1040.7 cm<s -1 、1407.1 cm -1 、2354.0 cm -1 、2896.4 cm -1 and 2987.2 cm -1 Among them, 445.6 cm -1 : It may be related to the vibration of the metal-oxygen bond (such as Ce-O) of cerium-containing compounds in the soil, suggesting that the cerium nitrate compound fertilizer acts in the soil to form related substances. 1040.7 cm -1 : Most likely corresponding to the Si-O-Si or Si-O-Al stretching vibrations of silicate minerals, indicating the presence of silicate mineral components in the soil. 1407.1 cm -1 : Or related to the vibrations of organic functional groups in the soil (such as the carboxyl group -COO-) and carbonates (C03 2- ), reflecting the situation of soil organic matter and carbonates. 2354.0 cm -1 : It may be affected by carbon dioxide in the air and may also be related to carbonates in the soil. 2987.2 cm -1 and 2896.4 cm -1: Corresponding to the C-H stretching vibrations of methyl (-CH3) and methylene (-CH2-) in organic matter, indicating the presence of organic components in the soil. Comparing with the spectrum of blank soil, the changes in some peak positions and intensities can reflect the effects of cerium nitrate compound fertilizer on the soil composition and structure.

[0062] By comparing the blank soil and the soil with cerium nitrate compound fertilizer, it can be seen that the cerium nitrate compound fertilizer has an impact on the chemical composition and structure of the soil. From the perspective of chemical bonds, it has changed the vibration characteristics of metal-oxygen, Si-O, C-H and other chemical bonds in the soil, indicating that the cerium element and other components in the compound fertilizer have undergone chemical reactions with the original substances in the soil. These changes may further affect the physical and chemical properties of the soil, such as the adsorption performance and ion exchange performance of the soil, and may also have a chain reaction on the migration and transformation of nutrients in the soil and the absorption and utilization of nutrients by plants.

[0063] 3.4 Raman spectroscopy-atomic force microscopy combined system analysis The Raman spectroscopy-atomic force microscopy combined system is an advanced analytical instrument system that combines Raman spectroscopy technology and atomic force microscopy technology. This system uses the probe of the atomic force microscope to perform high-precision topography imaging and mechanical property measurement on the sample surface at the nanoscale. At the same time, through Raman spectroscopy technology, the chemical structure and composition of the same position of the sample are analyzed. It can closely associate the microscopic topography information of the sample with the chemical composition information, provide comprehensive analysis from the nanoscale to the microscale, and has a wide range of applications in the fields of materials science, life science, nanotechnology, etc., which helps to deeply study the relationship between the structure and properties of the sample and the physical and chemical processes at the microscale. By identifying the coordination modes of rare earth ions and organic ligands through Raman spectroscopy characteristic peaks (such as the vibration peaks of Eu-O and Ce-N bonds), the formation and bonding strength of the complex are verified, and the core chemical structure of the light conversion function is supported. Figure 17 The Raman spectra of different soils are as follows: The Raman spectrum of the blank soil has 3 obvious characteristic peaks, and the wave numbers are approximately 3366.2 cm -1 、2166.2 cm -1 、1907.7 cm -1 These peaks correspond to the vibration modes of certain molecular groups in the soil and can be used to identify the inherent components in the soil, such as minerals and organic matter. For example, specific wave numbers may be related to the functional group vibrations of clay minerals and humus in the soil. The Raman spectrum of the blank soil reflects the molecular vibration information of the inherent components in the soil.

[0064] The Raman spectrum of the soil with cerium nitrate compound fertilizer also has three obvious characteristic peaks, which are 2812.3 cm -1 、1612.3 cm -1 and 1326.2 cm -1 . Among them, 2812.3 cm -1Peak at [1612.3 cm⁻¹]: It may be the characteristic peak of the new substance formed by the reaction of cerium nitrate compound fertilizer with soil components after its introduction. -1 Peak at [1326.2 cm⁻¹]: It may be related to the vibration of nitrate ions (NO₃⁻) or the vibration of some functional groups after the change of soil organic matter under the action of cerium nitrate. - ) -1 Peak at [2812.3 cm⁻¹ etc.]: It may correspond to the vibration characteristics of carbohydrates (such as polysaccharides, etc.) in the soil under the influence of cerium nitrate, or the vibration of some nitrogen-carbon-oxygen functional groups. Comparing the two spectra of the blank soil and the soil with cerium nitrate compound fertilizer, the positions and intensities of the peaks are significantly different. New peaks (such as 2812.3 cm⁻¹ etc.) appear in the spectrum of the soil with cerium nitrate compound fertilizer, and the intensities of some peaks also change. This indicates that after the application of cerium nitrate compound fertilizer to the soil, it has interacted with the original soil components, changing the molecular structure and chemical bond ring of the soil system.

[0065] 3.5 X-ray Diffractometer (XRD) Analysis An X-ray diffractometer is a scientific instrument. Its working principle is to use X-rays to irradiate the sample. When the X-rays hit the atoms and molecules in the sample, diffraction phenomena will occur, that is, the original propagation direction will be changed and scattered in different directions. The instrument will detect information such as the angles and intensities of these scattered X-rays. By analyzing this information, the crystal structure, composition, etc. of the sample can be known. Figure 18 XRD pattern of cerium nitrate compound fertilizer: There are fluctuations (instability) in the baseline of the pattern, which is particularly obvious in the low-angle region (such as below 20°), and may be caused by instrument noise, uneven sample scattering, or test environment interference (such as temperature, humidity). In the figure, by comparing with the standard XRD database (such as JCPDS cards), it can be preliminarily judged that: Low-angle peaks (2θ < 20°): may correspond to the 001 plane diffraction of layered minerals (such as clay minerals, montmorillonite, kaolinite, etc.), reflecting the layer spacing characteristics and indicating the presence of minerals with a layered structure in the sample. Medium-high angle peaks (around 2θ = 20° - 26.6°): If there are strong peaks, they may be the characteristic peaks of quartz (SiO₂) and need further confirmation. Other peaks: such as 23.48°, 27.50°, etc., may correspond to feldspar or carbonate minerals. The strong peak between 20° - 30° reflects the high-crystallinity region and corresponds to the crystal plane diffraction of montmorillonite; the low-angle peaks may be related to the interlayer disordered hydration structure, reflecting the expansibility of the soil. The higher the peak, the more the corresponding crystal content, or the more orderly the atomic arrangement on the crystal plane. The peaks on the left in the figure are relatively high, indicating that this kind of crystal may account for a large proportion in the sample.

[0066] Summary: (1)Selection of rare earth types: Cerium oxide, cerium nitrate, and cerium nitrate plus glycine were used for soil culture research respectively. Finally, according to various characterizations such as plant growth, pH, conductivity, root, stem, and leaf, it was confirmed that cerium nitrate plus glycine was used as the type of rare earth.

[0067] (2)Selection of cerium nitrate compound fertilizer types: Cerium nitrate compound fertilizers of cerium nitrate plus glycine, humic acid, and potassium dihydrogen phosphate were prepared respectively; soil culture research on cerium nitrate compound fertilizers of cerium nitrate plus glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate, cerium nitrate compound fertilizers of cerium nitrate and lanthanum nitrate compounded with glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate was carried out. Finally, according to various characterizations such as plant growth, pH, conductivity, root, stem, and leaf, it was confirmed that the cerium nitrate compound fertilizer of cerium nitrate plus glycine, mineral source fulvic acid potassium, wood vinegar liquid, and potassium dihydrogen phosphate was used.

[0068] (3)Single-factor research experiment: Cerium nitrate compound fertilizers with different concentrations were used, and the concentrations were 3 ml, 4 ml, 5 ml, 6 ml, and 7 ml respectively. At the same time, the application days of each fertilizer were determined: The application days of adding fertilizer for three days and four days were used. After observing for two weeks, according to various characterizations such as plant growth, pH, conductivity, root, stem, leaf, soil nitrogen, phosphorus, and potassium, scanning electron microscope, and specific surface area, the best conditions were obtained as follows: When 4 ml of cerium nitrate compound fertilizer was added, 140 g of saline-alkali soil, and the application days were 3 days, the effect was the best, the pH decreased from 8.6 to 7.4, the soil heavy metals were greatly reduced, and the soil nitrogen, phosphorus, and potassium increased significantly.

[0069] (4)Characterization analysis: After analysis by scanning electron microscope, specific surface area, Fourier transform infrared spectrometer, and Raman spectroscopy-atomic force microscope combined system, it was found that the application of cerium nitrate compound fertilizer changed the soil structure. The soil with cerium nitrate compound fertilizer applied was porous and loose, which was convenient for soil ventilation, water permeability, water retention, and fertilizer retention performance. The content of some functional groups increased, the soil fertility increased, and it also had a good removal effect on elements such as Fe and Si in the soil. It was also confirmed by infrared Raman and other characterizations that the compound fertilizer improved the soil composition under its action, which was more conducive to plant growth.

Claims

1. A rare earth cerium compound fertilizer, characterized in that, The rare earth cerium compound fertilizer is composed of the following components: cerium nitrate, glycine, mineral source fulvic acid potassium, wood vinegar liquid, potassium dihydrogen phosphate; By mass ratio, cerium nitrate is 5 parts - 15 parts, glycine is 10 parts - 20 parts, mineral source fulvic acid potassium is 20 parts - 30 parts, wood vinegar liquid is 10 parts - 20 parts, and potassium dihydrogen phosphate is 25 parts - 35 parts.

2. The rare earth cerium compound fertilizer according to claim 1, characterized in that, The purity of the cerium nitrate ≥ 99%, the purity of the mineral source fulvic acid potassium ≥ 75%, and the organic acid content of the wood vinegar liquid ≥ 99%.

3. The rare earth cerium compound fertilizer according to claim 1, characterized in that, The preparation method of the rare earth cerium compound fertilizer is as follows: (1) Dissolve cerium nitrate in deionized water and stir until completely dissolved to obtain a cerium nitrate solution; (2) Add glycine to the cerium nitrate solution and stir and react for 30 - 60 minutes to form a rare earth - amino acid complex; (3) Sequentially add mineral source fulvic acid potassium, wood vinegar liquid and potassium dihydrogen phosphate, stir and mix evenly to obtain a compound rare earth cerium fertilizer.

4. Use of the rare earth cerium compound fertilizer according to any one of claims 1-3 in improving saline-alkali soil, characterized in that, The rare earth cerium fertilizer is used to reduce the soil pH value, reduce the heavy metal content, increase the soil nitrogen, phosphorus and potassium nutrient content, increase the soil porosity, enhance the soil water and fertilizer retention capacity, promote plant root development and chlorophyll synthesis.

5. The application of the rare earth cerium compound fertilizer according to claim 4 in the improvement of saline-alkali soil, characterized in that, The application method is: apply the rare earth cerium compound fertilizer by potting at a dosage of 3 - 4 ml per 140 g of saline - alkali soil, and the application period is once every 3 days.

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