Lignosulfonate modified water-soluble fertilizer as well as preparation method and application thereof

Abstract

The invention provides a lignosulfonate modified water-soluble fertilizer as well as a preparation method and application thereof, and belongs to the technical field of fertilizer processing. The preparation method comprises the following steps: mixing lignosulfonate, organic acid, copper sulfate and water, reacting in a high-pressure closed environment at 170-185 DEG C for 45-100 minutes, cooling, adding a strong oxidant, reacting in the high-pressure closed environment at 180-185 DEG C for 120-150 minutes, cooling, and carrying out solid-liquid separation to obtain a liquid which is the lignosulfonate modified water-soluble fertilizer. According to the method, macromolecular chains of lignosulfonate are broken through acid and thermal hydrolysis processes, so that the molecular weight of lignosulfonate is obviously reduced, and meanwhile, the final product has an obvious growth promoting effect, promotes crop growth and increases the crop yield.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizer processing, and in particular relates to a lignin sulfonate modified water-soluble fertilizer and a preparation method and application thereof. Background Art

[0002] Lignin sulfonate, also known as sulfonated lignin, is a byproduct of sulfite papermaking wood pulp and a linear polymer compound. In agricultural production, the adsorption and slow-release properties of lignin sulfonate can better maintain the effectiveness of chemical fertilizers and enable them to be slowly released. It is a good organic compound fertilizer slow-release material. It contains many polycyclic polymer organic substances with negatively charged groups and has a strong affinity for high-valent metal ions in the soil. Using lignin sulfonate as a fertilizer carrier to adsorb or encapsulate fertilizers can achieve the purpose of fertilizer slow release.

[0003] Regarding the development and application of lignin sulfonate water-soluble fertilizer, the invention patent with application number 201010621733.9 discloses a clean and high-value utilization method for preparing fulvic acid and fertilizer from papermaking black liquor (the main component is lignin sulfonate), specifically, various straws or wood are used as raw materials for alkaline pulping, the obtained black liquor is concentrated and evaporated, peracetic acid and hydrogen peroxide solution are used as oxidants, and the concentrated black liquor is fully stirred and reacted at 50-90°C for 30-90 minutes for degradation; the reaction liquid is adjusted to pH 4-6 with acid, and then the fulvic acid solution is obtained by solid-liquid separation. In this technology, the papermaking black liquor can be fully utilized as a resource, which not only completely eliminates the pollution of the black liquor, but also converts it into high-value-added fulvic acid. At the same time, other solid wastes generated in the papermaking process are prepared into fertilizers, realizing the clean and high-value utilization of waste resources. U.S. Patent US 7198805 B2 discloses a method for producing humates, which can continuously produce humates with a high yield of useful products. The method produces humates by liquid-phase oxidation of a mixture of an alkaline reagent and a lignin-containing plant raw material (lignin or lignin sulfonate). The generated high molecular compound has carboxyl groups around it, which is conducive to the dissolution of the oxidation product in the alkali, making it similar to natural humic acid and humic acid produced from other raw materials.

[0004] Since lignin sulfonate is resistant to acid and hard water, it is usually defined as "plant fulvic acid" in the market. However, lignin sulfonate has a large molecular weight, exceeding 20,000 Daltons, which violates the definition of fulvic acid. And because lignin sulfonate has a small number of functional groups after entering the soil, its ion chelating ability is weaker than that of mineral potassium fulvic acid, and its ability to activate soil nutrients and promote growth is also much weaker than that of mineral fulvic acid. This leads to the fact that when used in drip irrigation, the amount of lignin sulfonate is much higher than that of mineral fulvic acid. For example, the amount of lignin sulfonate is generally 5-10kg / mu, while 200-300g / mu of mineral fulvic acid can produce a good growth-promoting effect.

[0005] Therefore, the research on how to increase the oxygen-containing functional groups on the structure of lignin sulfonate and transform the macromolecular structure into small molecules to enhance the effect of lignin sulfonate application on crops has great prospects. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a lignin sulfonate modified water-soluble fertilizer and its preparation method and application, through the acid and thermal hydrolysis process, the macromolecular chain of lignin sulfonate is broken, the molecular weight is significantly reduced, and the final product has an obvious growth-promoting effect.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A preparation method of a lignin sulfonate modified water-soluble fertilizer comprises the following steps: mixing lignin sulfonate, an organic acid, copper sulfate and water, reacting at 170-185°C for 45-100 minutes in a high-pressure sealed environment, adding a strong oxidant after cooling, reacting again at 180-185°C for 120-150 minutes in a high-pressure sealed environment, and separating the solid from the liquid after cooling, so that the liquid is the lignin sulfonate modified water-soluble fertilizer.

[0009] Preferably, the lignin sulfonate is a byproduct of sulfite papermaking wood pulp, including one or more of ammonium lignin sulfonate, sodium lignin sulfonate, and calcium lignin sulfonate.

[0010] Preferably, in parts by mass, the lignin sulfonate comprises 50-80 parts, the organic acid comprises 5.5-8.8 parts, the copper sulfate comprises 0.01-0.05 parts, and the water comprises 800-1000 parts.

[0011] More preferably, the organic acid comprises 5-8 parts of acetic acid, 0.3-0.5 parts of oxalic acid, and 0.2-0.3 parts of maleic acid, by mass.

[0012] Preferably, the strong oxidant is added in an amount of 20-30 parts by mass.

[0013] Preferably, the reaction is carried out in a hydrothermal reactor, and the stirring speed of the hydrothermal reactor is 150-250 rpm.

[0014] Preferably, the rotation speed of the solid-liquid separation is 3000-3500 rpm.

[0015] The invention also provides a lignin sulfonate modified water-soluble fertilizer prepared by the preparation method.

[0016] The invention also provides the use of the lignin sulfonate modified water-soluble fertilizer in the preparation of fertilizers and the use of the lignin sulfonate modified water-soluble fertilizer in crop cultivation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention provides a preparation method of lignin sulfonate modified water-soluble fertilizer. Through thermal hydrolysis and thermal oxidation processes, the weight average molecular weight of lignin sulfonate raw materials is significantly reduced to only 45.5% of the raw materials, and about 5% of pure lignin in the raw materials is removed.

[0019] The invention significantly increases the O / C ratio of lignin sulfonate, increases chemical functional groups such as carbonyl, carboxylic acid, phenolic hydroxyl and ester, and has stronger ion exchange and adsorption capabilities.

[0020] The lignin sulfonate modified water-soluble fertilizer prepared by the invention has a small dosage, for example, only 1 kg per mu is needed for drip irrigation of crops, which has the effect of obviously promoting plant growth and can also improve plant absorption of nutrients and crop yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Fourier transform infrared spectra of lignin sulfonate raw material (CK) and modified lignin sulfonate;

[0022] Figure 2 The effect of different fertilizer treatments on the growth of aboveground and underground parts of corn at the seedling stage. From left to right in the figure are cow dung compost extract treatment, lignin sulfonate treatment, lignin sulfonate modified water-soluble fertilizer treatment and CK;

[0023] Figure 3 This is the effect of different fertilizer treatments on corn growth. In the figure, the left side is CK and the right side is lignin sulfonate modified water-soluble fertilizer treatment. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing a lignin sulfonate modified water-soluble fertilizer to improve the application effect of lignin sulfonate, comprising the following steps:

[0025] (1) Mix lignin sulfonate, organic acid, copper sulfate and water.

[0026] In the present invention, preferably, lignin sulfonate is a byproduct of sulfite papermaking wood pulp, including one or more of ammonium lignin sulfonate, sodium lignin sulfonate, and calcium lignin sulfonate, including but not limited to the waste left after wheat straw, rice straw or other wood is used as the main raw material of paper pulp for papermaking. The above-mentioned lignin sulfonate is directly applied as a water-soluble fertilizer, and its molecular weight is large (more than 20,000 Daltons), and the binding sites of oxygen-containing functional groups are less than those of mineral-derived humic acid, and the ion binding buffering capacity is relatively weak, so there is a problem of large application amount and unobvious effect. The present invention uses organic acid and copper ions to modify it and optimize the application effect.

[0027] In the present invention, preferably, by mass, 50-80 parts of lignin sulfonate, 5.5-8.8 parts of organic acid, 0.01-0.05 parts of copper sulfate, 800-1000 parts of water; further preferably, the organic acid includes 5-8 parts of acetic acid, 0.3-0.5 parts of oxalic acid, and 0.2-0.3 parts of maleic acid; more preferably, 70 parts of lignin sulfonate, 8 parts of acetic acid, 0.3 parts of oxalic acid, 0.2 parts of maleic acid, 0.05 parts of copper sulfate, and 800 parts of water. In the lignin sulfonate, a large amount of cellulose, hemicellulose residues and lignin (unsulfonated) are combined on the macromolecules, and the cellulose and hemicellulose residues are hydrolyzed by a special ratio of organic acid and copper ions to produce monosaccharides such as glucose, xylose, arabinose, and galactose, and heated under acidic conditions for dehydration to generate furfural or its derivatives, and these small molecules are polymerized to generate dark brown substances (humic acid substances), which have obvious plant growth promotion effects.

[0028] (2) reacting at 170-185°C for 45-100 min in a high pressure sealed environment, and cooling after the reaction is completed; preferably reacting at 180°C for 75-80 min in a high pressure sealed environment; more preferably, the reaction is carried out in a hydrothermal reactor, and the stirring speed of the hydrothermal reactor is 150-250 rpm; more preferably, the stirring speed is 150-200 rpm. The high pressure in the present invention is a pressure>101.325 kPa.

[0029] In the present invention, the organic acid hydrolysis process is mainly used. Lignin sulfonate has a good pH buffering capacity. After adding organic acid, the pH of the reaction system is 4.8-5.0. In the hydrolysis process of the present invention, acetic acid is mainly used as a catalyst to promote the hydrolysis reaction of cellulose. It can provide hydrogen ions. After these hydrogen ions dissociate in water, they combine with the β-1,4-glucosidic bonds on the cellulose chain to break them, thereby decomposing cellulose into low-molecular polysaccharides and monosaccharides; oxalic acid has a good degradation effect, which can degrade the amorphous structure part in the wood cellulose molecular chain, thereby reducing the polymerization degree and crystallinity of cellulose; maleic acid can hydrolyze hemicellulose to generate xylose or other oligosaccharides; copper ions can promote the acid hydrolysis of cellulose. The present invention has a good effect of degrading fibers and hemicelluloses by combining the above three organic acids with copper sulfate in a certain proportion to react with lignin sulfonate, while removing lignin.

[0030] (3) After cooling in step (2), a strong oxidant is added, and the mixture is reacted again at 180-185° C. for 120-150 min in a high pressure closed environment, and cooled again after the reaction is completed. Preferably, the reaction is carried out in a hydrothermal reactor, and the stirring speed of the hydrothermal reactor is 150-250 rpm; more preferably, the stirring speed is 200-250 rpm.

[0031] In the present invention, the strong oxidant releases oxygen during the heating process, and the substrate is oxidized by the high temperature and high pressure environment + oxygen. Preferably, the addition amount of the strong oxidant is 20-30 parts by mass, more preferably 25 parts, and more preferably the strong oxidant is selected from one of hydrogen peroxide, ammonium persulfate, and peracetic acid.

[0032] (4) After cooling in step (3), solid-liquid separation is performed, and the liquid is a lignin sulfonate modified water-soluble fertilizer. Preferably, the rotation speed of solid-liquid separation is 3000-3500 rpm. The present invention uses the byproduct of sulfite papermaking wood pulp as raw material. After the process is completed, about 5% of lignin precipitation will appear, so it is removed by solid-liquid separation.

[0033] The invention also provides a lignin sulfonate modified water-soluble fertilizer prepared by the preparation method.

[0034] The present invention also provides the use of the above-mentioned lignin sulfonate modified water-soluble fertilizer in the preparation of fertilizers, including but not limited to direct processing into drip irrigation carbon fertilizer, or processing into other blended fertilizers as a raw material component. As an implementable embodiment, the content of the lignin sulfonate modified water-soluble fertilizer in the blended fertilizer is 0.1%-99.9%.

[0035] The present invention also provides the use of the above lignin sulfonate modified water-soluble fertilizer in crop cultivation; preferably, it is used as a drip irrigation water-soluble fertilizer and applied at the seedling stage of the crop; more preferably, the application amount is 1 kg / mu. As an implementation method, the crop is corn.

[0036] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0037] Example 1

[0038] A lignin sulfonate modified water-soluble fertilizer, the steps are as follows:

[0039] Mix lignin sulfonate (calcium lignin sulfonate), acetic acid, oxalic acid, maleic acid, copper sulfate and water in a certain mass ratio, the specific ratio is 50 parts: 5 parts: 0.3 parts: 0.2 parts: 0.05 parts: 1000 parts, and put them into a hydrothermal reactor and seal them. Set the stirring speed of the reactor to 200 rpm, the reaction temperature to 170 ° C, and react for 45 minutes. After the reaction is cooled, open the reactor, add 20 ml of hydrogen peroxide, and seal the reactor. Set the stirring speed of the reactor to 250 rpm, the reaction temperature to 180 ° C, and react for 120 minutes. After cooling, open the reactor, centrifuge for solid-liquid separation, and the liquid is the prepared product lignin sulfonate modified water-soluble fertilizer.

[0040] Example 2

[0041] A lignin sulfonate modified water-soluble fertilizer, the steps are as follows:

[0042] Mix lignin sulfonate (ammonium lignin sulfonate), acetic acid, oxalic acid, maleic acid, copper sulfate and water in a certain mass ratio, the specific ratio is 80 parts: 8 parts: 0.5 parts: 0.3 parts: 0.01 parts: 1000 parts, and put them into a hydrothermal reactor for sealing. Set the stirring speed of the reactor to 150rpm, the reaction temperature to 180℃, and react for 90min. After the reaction is cooled, open the reactor, add 30ml of peracetic acid, and seal the reactor. Set the stirring speed of the reactor to 200rpm, the reaction temperature to 185℃, and react for 150min. After cooling, open the reactor, centrifuge for solid-liquid separation, and the liquid is the prepared product, lignin sulfonate modified water-soluble fertilizer.

[0043] Example 3

[0044] A lignin sulfonate modified water-soluble fertilizer, the steps are as follows:

[0045] Mix lignin sulfonate (sodium lignin sulfonate and calcium lignin sulfonate), acetic acid, oxalic acid, maleic acid, copper sulfate and water in a certain mass ratio, the specific ratio is 70 parts: 5 parts: 0.5 parts: 0.3 parts: 0.01 parts: 900 parts, and put them into a hydrothermal reactor and seal them. Set the stirring speed of the reactor to 200 rpm, the reaction temperature to 185 ° C, and react for 100 minutes. After the reaction is cooled, open the reactor, add 30 ml of hydrogen peroxide, and seal the reactor. Set the stirring speed of the reactor to 250 rpm, the reaction temperature to 180 ° C, and react for 120 minutes. After cooling, open the reactor, centrifuge for solid-liquid separation, and the liquid is the prepared product lignin sulfonate modified water-soluble fertilizer.

[0046] Example 4

[0047] A lignin sulfonate modified water-soluble fertilizer, the steps are as follows:

[0048] Mix lignin sulfonate (sodium lignin sulfonate), acetic acid, oxalic acid, maleic acid, copper sulfate and water in a certain mass ratio, the specific ratio is 80 parts: 6 parts: 0.4 parts: 0.2 parts: 0.03 parts: 800 parts, and put them into a hydrothermal reactor and seal them. Set the stirring speed of the reactor to 180rpm, the reaction temperature to 170℃, and react for 100min. After the reaction is cooled, open the reactor, add 25ml of hydrogen peroxide, and seal the reactor. Set the stirring speed of the reactor to 230rpm, the reaction temperature to 185℃, and react for 140min. After cooling, open the reactor and centrifuge for solid-liquid separation. The liquid is the prepared product, lignin sulfonate modified water-soluble fertilizer.

[0049] Example 5

[0050] Comparison of infrared spectral characteristics of raw sodium lignin sulfonate (CK) and modified CK

[0051] The sodium lignin sulfonate raw material was purchased from Shenyang Xingzhenghe Chemical Co., Ltd.; the modified raw material was the lignin sulfonate modified water-soluble fertilizer prepared in Example 4.

[0052] Tested by Shanghai Fuda Testing Technology Group Co., Ltd., report number: FT-20240819109, the results are as follows Figure 1 shown.

[0053] according to Figure 1 It can be seen that at 4000-1500cm -1 Wave number band, the infrared spectra characteristic absorption peaks of the two samples are almost completely consistent; in the range of 500-1500cm -1 Wave number band, there are some differences in the characteristic absorption peaks of the infrared spectra of the two samples, and 500-1500cm -1 Within the range of wave number bands, the vibration and bending of substances produce absorption peaks, which are usually called fingerprint peaks; 900-1500cm -1 In the range of wave number bands, the absorption peak is usually located between the vibration-bending peaks, and the two samples are at 990 cm -1 、1220cm -1 The peaks at 680 cm-1 are obviously different, and these peaks are usually related to chemical functional groups such as carbonyl, carboxylic acid, phenolic hydroxyl, and ester. -1 The above results show that the process of the present invention causes structural differences in sodium lignin sulfonate.

[0054] Example 6

[0055] Comparison of molecular weight distribution and elemental composition of raw sodium lignin sulfonate (CK) and modified CK

[0056] The sodium lignin sulfonate raw material was purchased from Shenyang Xingzhenghe Chemical Co., Ltd.; the modified raw material was the lignin sulfonate modified water-soluble fertilizer prepared in Example 4.

[0057] The molecular weight distribution was measured by gel permeation chromatography system GPC (Agilent PL-GPC220), tested by Shanghai Fuda Testing Technology Group Co., Ltd., report number: FT-20240819109, as shown in Table 1.

[0058] Table 1 Difference in molecular weight distribution of sodium lignin sulfonate raw material (CK) and modified

[0059] PeakNo Mp Mn M Mz Mz+1 Mv PD CK 475 810 2963 17891 36249 2179 3.65802 Modification 1696 1137 1349 1538 1728 1320 1.18646

[0060] In the table, Mp: peak molecular weight; Mn: number average molecular weight; Mw: mass average molecular weight (weight average molecular weight); Mz: polydispersity molecular weight; Mz+1: high molecular weight; Mv: viscosity average molecular weight; PD: molecular weight distribution index.

[0061] According to Table 1, it can be seen that the mass average molecular weight (weight average molecular weight Mw) decreased from 2963 g / mol of the control to 1349 g / mol, with a decrease of 54.5%; the molecular weight distribution index (PD) decreased from 3.66 to 1.19, and the PD value after treatment was close to 1, indicating that the molecular weight of the polymer was relatively uniform. The above results show that after the process of the present invention, the molecular weight of sodium lignin sulfonate changes, the polymerized molecular chain is broken and becomes a short chain, and the molecules are relatively uniform.

[0062] The elemental composition was determined by an organic element analyzer (UNICUBE element analyzer) using the CHNS mode and oxygen mode, as shown in Table 2.

[0063] Table 2 Differences in elemental composition between raw sodium lignin sulfonate (CK) and modified

[0064]

[0065] The molar ratio of elements can characterize the oxidation degree and aromaticity of lignin humic acid to a certain extent. According to Table 2, it can be seen that the samples treated by the process of the present invention have a higher O content, a lower C content, and a higher O / C.

[0066] Example 7

[0067] Through hydroponic experiments, the effects of nutrient solutions from different sources on the growth of corn seedlings were evaluated, and whether lignin sulfonate-modified water-soluble fertilizers have agricultural application prospects were evaluated.

[0068] Materials and Methods

[0069] (1) Test materials

[0070] The four treatments were sodium lignin sulfonate treatment (LS treatment), lignin sulfonate modified water-soluble fertilizer treatment (modified LS treatment), cow dung compost extract treatment and CK; the four treatments had the same levels of N, P2O5, K2O + trace elements.

[0071] Among them, the sodium lignin sulfonate raw material was purchased from Shenyang Xingzhenghe Chemical Co., Ltd.; the modified lignin sulfonate modified water-soluble fertilizer was prepared in Example 4; and the cow dung compost extract was prepared by catalytic oxidation-alkali dissolution and acid precipitation method (DOI: 10.19451 / j.cnki.issn1671-9212.2006.06.014.).

[0072] (2) Test methods

[0073] Sodium lignin sulfonate, lignin sulfonate modified water-soluble fertilizer and cow dung compost extract were diluted 20,000 times respectively to prepare nutrient solution. Prepare potting soil for placing corn seeds to ensure good contact between seeds and soil. Set up a transparent container under the potting soil and fill it with an appropriate amount of nutrient solution. Keep it ventilated to ensure that the nutrient solution has sufficient oxygen content, which is conducive to root respiration. During the prescribed growth cycle, regularly replenish the nutrient solution to maintain its concentration and cleanliness. CK supplements the same amount of water.

[0074] (3) Measurement indicators

[0075] A few days after corn was planted, its aboveground biomass (including stems, leaves, etc.) and underground biomass (root system) were measured.

[0076] Test results.

[0077] according to Figure 2 As shown in Table 3, different treatments had different effects on the biomass of the aboveground and underground parts of corn. Under the CK treatment, the weight of the aboveground part of corn was 0.51 g. In contrast, the modified LS treatment significantly increased the weight of the aboveground part (P<0.05), with an increase of 27.48%, which was the best performance. The cow dung compost extract treatment also brought a positive effect, with an increase of 12.27% in the aboveground weight, while the LS treatment had almost no effect on the aboveground weight, with an increase of only -0.27%, which can be regarded as no change. For the weight of the underground part, the CK treatment was 0.04 g. Both the modified LS treatment and the cow dung compost extract treatment significantly promoted the growth of the underground part, increasing by about 50%. The LS treatment had no significant effect on the weight of the underground part (P>0.05). Overall, the modified LS treatment performed best in increasing the biomass of the individual plant, with an increase of up to 29.19%. The cow dung compost extract treatment increased by 14.82%, which was second. The LS treatment had no significant effect on the biomass of the individual plant.

[0078] In addition, the root-to-shoot ratio of the CK treatment was 0.08, indicating that under the control conditions, the biomass of the aboveground part of the plant was relatively large, while the biomass of the underground part accounted for a small proportion. The root-to-shoot ratio of the modified LS treatment increased to 0.10, which was an increase compared with CK. This shows that the modified LS treatment promoted the growth of the root system, which increased the resource allocation of the plant to the underground part, thereby improving the growth potential of corn. The LS treatment did not change the root-to-shoot ratio of the plant, which was the same as CK, at 0.08. The cow dung compost extract treatment had the highest root-to-shoot ratio of 0.11, indicating that the cow dung compost extract treatment significantly promoted the growth of the root system.

[0079] Table 3 Effects of different nutrient solution treatments on corn seedling growth

[0080]

[0081] In summary, it can be seen that the modified LS treatment and cow dung compost extract treatment have the best effect in promoting the growth of the aboveground and underground parts of plants and increasing biomass, and the cow dung compost extract treatment has the most significant effect on improving the root-to-shoot ratio. This shows that these two treatments can improve the growth of plants by promoting the growth of the root system, while the LS treatment has no significant contribution to the growth of plant biomass and root-to-shoot ratio.

[0082] Example 8

[0083] By comparing and analyzing the effects of sewage sludge humic acid, mineral humic acid and lignin sulfonate modified water-soluble fertilizer treatments on maize seedling biomass and nutrient absorption at different concentration gradients, the author evaluated whether lignin sulfonate modified water-soluble fertilizer has agricultural application prospects.

[0084] Materials and Methods

[0085] (1) Test materials

[0086] Humic acid extract: sewage sludge fulvic acid, mineral potassium humate and lignin sulfonate modified water-soluble fertilizer (modified LS); corn seeds.

[0087] Among them, sludge fulvic acid and mineral potassium humate were purchased from Shenyang Xingzhenghe Chemical Co., Ltd.; and the modified fertilizer was the lignin sulfonate modified water-soluble fertilizer prepared in Example 4.

[0088] (2) Test methods

[0089] At the beginning of the experiment, the soil corresponding to each treatment was evenly placed in a flower pot, with a soil weight of 15 kg per pot and 5 pots per treatment. Five corns were planted in each pot. Nitrogen fertilizer and phosphorus and potassium fertilizer were used for topdressing, where nitrogen fertilizer was 150 mg / kg urea and phosphorus and potassium fertilizer was 75 mg / kg potassium dihydrogen phosphate, which were prepared according to the air-dried soil weight to prepare a nutrient solution.

[0090] The lignin sulfonate modified water-soluble fertilizer and sludge humic acid were diluted 10,000 times and 20,000 times, respectively, and the mineral potassium humate was diluted 15,000 times and 30,000 times (equal cost design); each treatment was defined as CK, sludge humic acid low concentration (L) treatment, sludge humic acid high concentration (H) treatment, modified LS low concentration (L) treatment, modified LS high concentration (H) treatment, mineral potassium humate low concentration (L) treatment, mineral potassium humate high concentration (H) treatment. The above treatments were mixed with nutrient solution topdressing.

[0091] (3) Measurement indicators

[0092] Thirty days after corn planting, growth indicators (including aboveground and underground dry weight) and plant nutrient content (nitrogen, phosphorus, and potassium) were measured using conventional methods. Excel 2019 was used to process relevant data and conduct significance analysis.

[0093] Test results.

[0094] (1) Effects of different treatments on maize seedling biomass

[0095] The biomass and increase rate of corn seedlings under each treatment are shown in Table 4.

[0096] Table 4 Biomass and variation of maize seedlings under different treatments

[0097]

[0098]

[0099] According to Table 4, sludge fulvic acid, modified LS and mineral potassium humate all have a positive effect on the growth of the underground part of plants, and the effects of different treatments at different concentrations are different. The modified LS treatment increased the dry weight of the underground part at both concentrations, and with the increase in concentration, the increase in the dry weight of the underground part increased from 12.08% to 14.73%, reaching a significant difference (P<0.05); this shows that the modified LS has a promoting effect on the growth of plant roots, and the effect increases with the increase in concentration. The mineral potassium humate treatment has the most significant effect on the increase in the dry weight of the underground part, especially at high concentrations, the dry weight of the underground part increased by 26.09%, which is much higher than other treatments. The sludge fulvic acid treatment increased the dry weight of the aboveground part at both concentrations, but the increase was weakened when the concentration increased, and the increase was reduced from 15.28% to 11.86%, which means that the excessive concentration of sludge fulvic acid may have a certain inhibitory effect on the growth of the aboveground part. The modified LS treatment weakened with the increase of concentration, and even at high concentration, the aboveground part increased by -4.81%, which was the only treatment with negative growth, indicating that high concentrations of modified LS may inhibit the growth of aboveground parts, and there is an optimal concentration range. The effect of low concentration modified LS treatment on the biomass of corn plants was significantly different from that of the control (P<0.05), and the biomass increase reached more than 12%. Figure 3 As shown, but there was no difference between the high concentration and the control (P>0.05).

[0100] (2) Effects of different treatments on nutrient absorption of maize seedlings

[0101] The nutrient absorption of corn seedlings under each treatment is shown in Table 5.

[0102] Table 5 Nutrient absorption status of maize seedlings under different treatments

[0103]

[0104] According to Table 5, all three treatments have a certain effect on plant nutrient absorption. Compared with the control, many indicators show significant differences (P<0.05). Among them, the high concentration of sludge humic acid treatment has a 40%-50% increase in total nitrogen, phosphorus and potassium absorption, which is the best performance; the low concentration of modified LS treatment has a 17.7%-40% increase in total nitrogen, phosphorus and potassium absorption, and the total phosphorus absorption is relatively high, reaching an increase of 40%, and the other nutrients are 17.7% and 20.15% respectively; while the high concentration of modified LS treatment has a total nitrogen, phosphorus and potassium absorption increase of only 3.5-14.6%; the high concentration of mineral potassium humate treatment has a higher absorption of total nitrogen, total phosphorus and potassium of 21% and 26%.

[0105] In summary, it can be seen that low-concentration treatment of modified LS can effectively increase the biomass of corn seedlings, promote plant root growth, and improve the soil nutrient absorption capacity. However, high-concentration treatment has a certain inhibitory effect on corn growth. Therefore, attention should be paid to its dosage during agricultural application.

[0106] Example 9

[0107] Through drip irrigation, the effects of sodium lignin sulfonate (LS) and lignin sulfonate modified water-soluble fertilizer (modified LS) on corn yield were analyzed, and whether lignin sulfonate modified water-soluble fertilizer has agricultural application prospects was evaluated.

[0108] Materials and Methods

[0109] (1) Test materials

[0110] The sodium lignin sulfonate raw material was purchased from Shenyang Xingzhenghe Chemical Co., Ltd.; the modified raw material was the lignin sulfonate modified water-soluble fertilizer prepared in Example 4.

[0111] (2) Test methods

[0112] Five treatments were set up on the basis of the same phosphorus and potassium (P2O5 150kg / hm2, K2O 75kg / hm2). Treatment 1: conventional fertilization (CK); Treatment 2: conventional fertilization (CK) + 1kg LS; Treatment 3: conventional fertilization (CK) + 5kg LS; Treatment 4: conventional fertilization (CK) + 1kg modified LS. After the corn seedlings were completed, drip irrigation was carried out on May 20, and each treatment was repeated 3 times. The plot area was 200m 2 .

[0113] (3) Measurement indicators

[0114] After the corn matures, the yield is measured, including the number of ears per mu, the number of grains per ear, the grain weight per ear, and the yield per mu.

[0115] Test results

[0116] According to Table 6, there is no significant difference in the number of corn plants in each treatment (P>0.05). The grain weight per plant in treatment 3 and treatment 4 is significantly greater than that in CK treatment, among which treatment 4 has the largest grain weight, which is 179.09g / plant, significantly higher than CK and treatment 2 (P<0.05); there is no significant difference between CK and treatment 2 (P>0.05); compared with CK, treatment 3 and treatment 4 both significantly increase corn yield (P<0.05), with an increase of 6.73% and 8.12% respectively.

[0117] Table 6 Corn yield under drip irrigation with different water-soluble fertilizers

[0118]

[0119]

[0120] The above results show that the modified LS can increase corn yield under drip irrigation conditions, the yield increase reaches a significant difference, and the yield increase effect is better than that of the unmodified LS.

[0121] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a lignin sulfonate modified water-soluble fertilizer, characterized in that: The following steps are involved: Mix lignin sulfonate, organic acid, copper sulfate and water, react at 170-185°C for 45-100 minutes in a high-pressure sealed environment, add a strong oxidant after cooling, react again at 180-185°C for 120-150 minutes in a high-pressure sealed environment, separate the solid and the liquid after cooling, and the liquid is a lignin sulfonate modified water-soluble fertilizer.

2. The preparation method according to claim 1, characterized in that: The lignin sulfonate is a byproduct of sulfite papermaking wood pulp, including one or more of ammonium lignin sulfonate, sodium lignin sulfonate, and calcium lignin sulfonate.

3. The preparation method according to claim 1, characterized in that: In parts by mass, the lignin sulfonate comprises 50-80 parts, the organic acid comprises 5.5-8.8 parts, the copper sulfate comprises 0.01-0.05 parts, and the water comprises 800-1000 parts.

4. The preparation method according to claim 3, characterized in that: In parts by mass, the organic acid includes 5-8 parts of acetic acid, 0.3-0.5 parts of oxalic acid, and 0.2-0.3 parts of maleic acid.

5. The preparation method according to claim 1, characterized in that: The added amount of the strong oxidant is 20-30 parts by mass.

6. The preparation method according to claim 1, characterized in that: The reaction is carried out in a hydrothermal reactor, and the stirring speed of the hydrothermal reactor is 150-250 rpm.

7. The preparation method according to claim 1, characterized in that: The rotation speed of the solid-liquid separation is 3000-3500rpm.

8. The lignin sulfonate modified water-soluble fertilizer obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the lignin sulfonate modified water-soluble fertilizer according to claim 9 in the preparation of fertilizers.

10. Use of the lignin sulfonate modified water-soluble fertilizer according to claim 9 in crop cultivation.

Images