A preparation for activating sparingly soluble phosphorus in soil and its application method

Abstract

The invention discloses a preparation for activating insoluble phosphorus in soil and an application method thereof. The preparation comprises the following components in parts by weight: 50-60 parts of activated biochar, 20-30 parts of modified starch, 3-4 parts of sodium alginate and 3-5 parts of calcium chloride. The preparation is prepared by the following method: adding modified starch, sodium alginate and deionized water into a reaction kettle, adding deionized water, then adding activated biochar, mixing, dripping the mixed solution into a calcium chloride solution, filtering and precipitating, washing and freeze-drying, and obtaining the preparation. The preparation increases the stability of soil aggregates, improves the adsorption of insoluble phosphorus by soil aggregates, makes metal ions on insoluble phosphorus adsorbed by the preparation, activates insoluble phosphorus by competitive binding of metal ions, and synergizes with phosphate-solubilizing bacteria to activate insoluble phosphorus in soil aggregates.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphorus activation, and in particular relates to a preparation for activating sparingly soluble phosphorus in soil and an application method thereof. Background Art

[0002] Phosphorus is an important element in the growth and development of plants. Phosphorus deficiency can lead to a series of growth and development problems and production problems in plants. However, the effectiveness of phosphorus in the soil is poor. Currently, phosphorus is provided to crops by excessive application of phosphorus fertilizers. However, the utilization rate of phosphorus fertilizers by crops in the current season is low, only 10%-25%. Most of the phosphorus fertilizers are chelated by metal ions such as calcium, iron, and aluminum in the soil to form insoluble phosphorus, which is fixed in the soil and difficult to be used by plants. Currently, phosphorus can only be provided to crops through multiple applications of phosphorus fertilizers. However, excessive application of phosphorus fertilizers will aggravate the runoff and leaching losses of phosphorus in farmland, and easily cause agricultural non-point source pollution.

[0003] Patent CN109777438A discloses a preparation for activating phosphorus in soil, and its preparation method, application method and application. Through the synergistic promotion of Cladosporium fungi and inorganic nanomaterials, and the reuse of sodium nitrophenolate, the secretion of phospholytic enzymes such as phytase and phosphatase in the soil is promoted, and the original insoluble phosphorus in the soil is released as fast-acting phosphorus. However, this scheme activates the root activity of crops through inorganic nanomaterials and sodium nitrophenolate, thereby increasing the absorption of phosphorus by rice. It needs to be effective after the crops grow roots, and the application is difficult and limited by the types of crops and the activation capacity of crops.

[0004] Patent CN107162852A discloses a soil phosphorus activator and its preparation method and application. The method activates the sparingly soluble phosphorus in the soil by applying phosphate-solubilizing microorganisms into the soil under the protection of a carrier. However, the phosphorus activation rate of this scheme is slow, and it depends on the activity of the phosphate-solubilizing microorganisms and their distribution in the soil. In addition, the phosphorus retention effect is poor in the initial stage of phosphate fertilizer application.

[0005] After the first application of water-soluble phosphate fertilizer, the water-soluble phosphorus content in the soil is high, but it will soon chelate with metal ions in the soil and precipitate to convert into insoluble phosphorus. After watering again, the amount of phosphorus dissolved in the soil is less. Therefore, a preparation is needed that can activate the insoluble phosphorus in the soil, increase the content of soluble phosphorus in the soil, and reduce the conversion of water-soluble phosphorus into insoluble phosphorus to meet the soil's demand for phosphorus and avoid the problem of excessive phosphorus caused by repeated fertilization. Summary of the invention

[0006] The object of the present invention is to provide a preparation and application method for activating sparingly soluble phosphorus in soil;

[0007] The first technical problem to be solved is: how to activate the sparingly soluble phosphorus in the soil;

[0008] The second technical problem to be solved is: reducing the conversion of water-soluble phosphorus in the soil into insoluble phosphorus;

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A preparation for activating sparingly soluble phosphorus in soil, comprising the following components in parts by weight:

[0011] 50-60 parts of activated biochar, 20-30 parts of modified starch, 3-4 parts of sodium alginate, 3-5 parts of calcium chloride;

[0012] The preparation is prepared by the following method:

[0013] Sodium alginate and deionized water are added into a reactor to prepare a 3-4 wt% sodium alginate solution, and then modified starch is added and mixed, the reactor is heated to 30-40° C. and stirred at a stirring rate of 500-600 rpm for 30-60 min, and then activated biochar is added into the reactor and mixed, and then the solution in the reactor is dripped into a 3-5 wt% calcium chloride solution using a syringe pump with a needle diameter of 1.2-1.6 mm, and the precipitate is filtered, and the precipitate is washed with deionized water and freeze-dried to obtain a preparation;

[0014] Furthermore, activated biochar is prepared by the following steps: placing rice straw with a particle size of ≤1 mm and deionized water in a reactor, heating to 190-210°C for reaction for 8-10 hours, filtering after cooling, washing the precipitate, and then evenly spraying the mixed bacterial solution on the surface of the precipitate, and obtaining activated biochar after drying at 30-40°C.

[0015] Furthermore, the mixed bacterial liquid is prepared by mixing equal volumes of starch-degrading bacterial fermentation liquid and phosphate-solubilizing microbial fermentation liquid.

[0016] Further, starch degrading bacteria include but are not limited to Bacillus, Bifidobacterium and Lactobacillus, and in this embodiment, Bacillus amyloliquefaciens is preferred; phosphate-solubilizing microorganisms include but are not limited to phosphate-solubilizing bacteria, phosphate-solubilizing fungi and phosphate-solubilizing actinomycetes, and in this embodiment, Bacillus megaterium is preferred;

[0017] Furthermore, the starch-degrading bacteria fermentation broth and the phosphate-solubilizing microorganism fermentation broth are prepared by conventional seed tank expansion culture method, and the number of bacterial species in the prepared fermentation broth is greater than 8x10 8 cfu / mL.

[0018] Furthermore, the usage ratio of rice straw, deionized water and mixed bacterial solution is 100-150 g: 150-200 mL: 4-5 mL.

[0019] Furthermore, the modified starch is prepared by the following steps: adding oxalate corn starch, sodium citrate and boric acid into a reaction kettle, adding deionized water, heating to 40-50° C., stirring for 15-20 minutes, cooling to room temperature, and spray drying to obtain the modified starch.

[0020] Furthermore, the usage ratio of oxalate corn starch, sodium citrate, boric acid and deionized water is 20-30 g: 5-8 g: 0.5-1 g: 100-120 mL.

[0021] Further, oxalate corn starch is prepared by the following steps:

[0022] In a reaction kettle, oxalic acid is dissolved in dimethyl sulfoxide, dried corn starch is added to the reaction kettle, and then benzene and pyridine are added respectively, and the mixture is stirred at 75-100° C. for 2-4 hours, and after cooling to room temperature, ethanol is added and stirred to obtain a precipitate, and the precipitate is filtered and washed with 50wt% ethanol until the last washing liquid is neutral, and the precipitate is dried at 90-100° C. for 12-24 hours, and ground through an 80-100 mesh sieve to obtain oxalic acid corn starch.

[0023] Furthermore, the mass ratio of oxalic acid, dimethyl sulfoxide, corn starch, benzene and pyridine is 10-15:20-25:20-30:100-300:0.1-0.15.

[0024] A method of applying a preparation for activating sparingly soluble phosphorus in soil is:

[0025] The preparation is administered at 25-40 kg / hm 2 Apply the application amount into the soil at a depth of 5-10cm, sprinkle water to make the soil moisture content at a depth of 5-10cm reach 30-40%, and the application is completed.

[0026] Furthermore, the application method can also be: the phosphate fertilizer to be applied is mixed with the preparation at a mass ratio of 10:3-5 and then applied to the soil at a depth of 5-10 cm, and then watered to make the soil moisture at a depth of 5-10 cm reach 30-40%, and the application is completed.

[0027] Beneficial effects of the present invention:

[0028] (1) The preparation of the present invention forms a water film around soil particles by absorbing water through sodium alginate to increase the stability of soil aggregates, thereby improving the adsorption of insoluble phosphorus by soil aggregates, making the insoluble phosphorus more evenly dispersed in the soil. The metal ions on the insoluble phosphorus in the soil aggregates are adsorbed by the preparation, and the insoluble phosphorus is activated by competitive binding with the metal ions, and synergistically acts with phosphate-solubilizing bacteria to activate the insoluble phosphorus in the soil aggregates.

[0029] (2) When the preparation of the present invention is applied together with phosphate fertilizer, the formation of insoluble phosphorus in the soil is reduced by adsorbing and slowly releasing the phosphate fertilizer. The preparation reduces the combination of phosphate fertilizer and metal ions by chelating metal ions in the soil. The stability of aggregates in the soil is increased by biochar, thereby improving the adsorption of insoluble phosphorus by aggregates. Insoluble phosphorus is converted into soluble phosphorus under the action of phosphate-solubilizing bacteria, thereby reducing the conversion of newly applied phosphate fertilizer into insoluble phosphorus and activating insoluble phosphorus in the soil into soluble phosphorus, thereby achieving the purpose of increasing the soluble phosphorus content in the soil.

[0030] (3) The activated biochar in the preparation of the present invention is prepared by a hydrothermal method, so that the surface of the obtained biochar contains rich functional groups, which not only improves the adsorption capacity of the biochar, but also facilitates the cross-linking reaction with the modified starch, making the modified starch and the activated biochar more firmly combined.

[0031] (4) The modified starch in the preparation of the present invention is obtained by cross-linking corn starch with sodium citrate after oxalic acid esterification. The degree of oxalic acid esterification of the corn starch of the present invention is low, which improves the adsorption and coordination capacity, and makes the corn starch easier to decompose into glucose for utilization by microorganisms, thereby promoting the growth of the bacterial agent. In addition, the oxalic acid group can still chelate with metal ions after the starch is degraded, thereby promoting the release of phosphorus in the soil. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1:

[0034] A preparation for activating sparingly soluble phosphorus in soil, comprising the following components in parts by weight:

[0035] 5kg activated biochar, 2kg modified starch, 0.3kg sodium alginate, 0.3kg calcium chloride;

[0036] Activated biochar is produced by the following steps:

[0037] 10 kg of rice straw with a particle size of ≤ 1 mm and 15 L of deionized water were placed in a reactor, heated to 190 °C for reaction for 8 h, filtered after cooling, and the precipitate was washed with deionized water and ethanol in turn until the washing liquid was transparent. Then 400 mL of the mixed bacterial solution was evenly sprayed on the surface of the precipitate and dried at 30 °C to obtain activated biochar.

[0038] The mixed bacterial liquid is prepared by mixing equal volumes of starch-degrading bacterial fermentation liquid and phosphate-solubilizing microbial fermentation liquid;

[0039] Starch degrading bacteria include but are not limited to Bacillus, Bifidobacterium and Lactobacillus. In this embodiment, Bacillus amyloliquefaciens is preferred, which was purchased from Shandong Yihao Biotechnology Co., Ltd.

[0040] Phosphate-solubilizing microorganisms include, but are not limited to, phosphate-solubilizing bacteria, phosphate-solubilizing fungi, and phosphate-solubilizing actinomycetes. In this embodiment, phosphate-solubilizing Bacillus megaterium is preferred, which was purchased from Shandong Nuojie Biotechnology Co., Ltd.;

[0041] The starch-degrading bacteria fermentation broth and the phosphate-dissolving microorganism fermentation broth were prepared by conventional seed tank expansion culture method, and the number of bacterial species in the prepared fermentation broth was greater than 8x10 8 cfu / mL.

[0042] The surface of hydrothermal biochar produced by the hydrothermal method contains abundant oxygen-containing functional groups such as OH, C=O, COOH, -COC-, which are helpful for cross-linking reaction and can increase the organic carbon concentration in the soil. Because the biochar particle size is small, it can increase the content of microaggregates and mesoaggregates in the soil, and can also provide a growth environment for microorganisms and promote their growth. Rice straw hydrothermal biochar also has excellent adsorption capacity for heavy metal ions in the soil, which helps to activate the insoluble phosphorus in the soil.

[0043] Oxalic acid corn starch is prepared by the following steps:

[0044] Dissolve 1 kg of oxalic acid in 2 kg of dimethyl sulfoxide in a reactor, add 2 kg of dry corn starch into the reactor, and then add 10 kg of benzene and 10 g of pyridine respectively, stir and react at 75°C for 2 hours, cool to room temperature, add 1 kg of ethanol and stir, filter the precipitate and wash the precipitate with 50 wt% ethanol until the last washing liquid is neutral, dry the precipitate at 90°C for 12 hours, grind through an 80-mesh sieve to obtain oxalic acid corn starch.

[0045] After corn starch is modified with oxalic acid, it contains carboxyl groups. Carboxyl corn starch has good adsorption and coordination ability, which can adsorb metal ions in the soil to form complexes and reduce the soil's sensitivity to HPO4. 2- and H2PO4 - The chemical fixation effect of the starch is strong, but the high carboxyl corn starch has strong hydrophilicity and will compete with sodium alginate for water absorption. Therefore, the low carboxyl corn starch not only grafts oxalate, improves the ability to chelate metal ions, but also has a lower competitive effect with sodium alginate, and does not affect the sustained release effect of sodium alginate.

[0046] The molecular chains of corn starch modified by oxalate are opened, making it easier to be degraded by microorganisms and bacteria in the soil as a carbon source. The oxalic acid groups in the degraded oxalic acid corn starch can continue to chelate metal cations such as calcium ions in the soil, thereby effectively promoting the release of insoluble phosphorus.

[0047] Modified starch is prepared by the following steps:

[0048] 2 kg of oxalate corn starch, 0.5 kg of sodium citrate and 50 g of boric acid were added into a reactor, and 10 L of deionized water was added. The temperature was raised to 40° C., stirred for 15 min, cooled to room temperature, and spray-dried to obtain modified starch.

[0049] The surface of low-carboxylated corn starch also contains abundant hydroxyl functional groups, and the surface of sodium citrate also contains hydroxyl functional groups, which can form hydrogen bonds, so that sodium citrate and corn starch form a cross-linked structure;

[0050] The cross-linking density of oxalic acid corn starch was increased after hydrogen bonding with sodium citrate, which increased the metal chelating ability and the sedimentation ability in the soil.

[0051] A method for preparing a preparation for activating sparingly soluble phosphorus in soil comprises the following steps:

[0052] 2 kg of modified starch, 0.3 kg of sodium alginate and 10 L of deionized water were added to a reactor, the temperature was raised to 30 ° C and stirred at a stirring rate of 500 rpm for 30 min, and then 5 kg of activated biochar was added to the reactor and mixed. The solution in the reactor was dripped into 10 L of 3 wt% calcium chloride solution using a syringe pump with a needle diameter of 1.2 mm. The precipitate was filtered, washed with deionized water and freeze-dried to obtain a preparation.

[0053] Embodiment 2:

[0054] A preparation for activating sparingly soluble phosphorus in soil, comprising the following components in parts by weight:

[0055] 5.5kg activated biochar, 2.5kg modified starch, 0.35kg sodium alginate, 0.4kg calcium chloride;

[0056] Activated biochar is produced by the following steps:

[0057] 12.5 kg of rice straw with a particle size of ≤1 mm and 17.5 L of deionized water were placed in a reactor, heated to 200 °C for reaction for 9 h, filtered after cooling, and the precipitate was washed with deionized water and ethanol in turn until the washing liquid was transparent. Then 450 mL of the mixed bacterial solution was evenly sprayed on the surface of the precipitate and dried at 35 °C to obtain activated biochar.

[0058] The mixed bacterial liquid is prepared by mixing equal volumes of fermentation liquid of Bacillus amyloliquefaciens and fermentation liquid of Bacillus megaterium phosphate-solubilizing;

[0059] The fermentation broth of Bacillus amyloliquefaciens and Bacillus megaterium phosphate-solubilizing was prepared by conventional seed tank expansion culture method, and the number of bacterial species in the prepared fermentation broth was greater than 8x108 cfu / mL.

[0060] Oxalic acid corn starch is prepared by the following steps:

[0061] In a reaction kettle, 1.25 kg of oxalic acid was dissolved in 2.25 kg of dimethyl sulfoxide, 2.5 kg of dry corn starch was added to the reaction kettle, and 20 kg of benzene and 12.5 g of pyridine were added respectively, and the mixture was stirred at 85° C. for 3 hours. After cooling to room temperature, 2 kg of ethanol was added and stirred. The precipitate was filtered and washed with 50 wt% ethanol until the last washing liquid was neutral. The precipitate was dried at 95° C. for 18 hours, and ground through an 80-mesh sieve to obtain oxalic acid corn starch.

[0062] Modified starch is prepared by the following steps:

[0063] 2.5 kg of oxalate corn starch, 0.65 kg of sodium citrate and 75 g of boric acid were added into a reactor, and 11 L of deionized water was added. The temperature was raised to 45° C., stirred for 17.5 min, cooled to room temperature, and spray-dried to obtain modified starch.

[0064] A method for preparing a preparation for activating sparingly soluble phosphorus in soil comprises the following steps:

[0065] 2.5 kg of modified starch, 0.35 kg of sodium alginate and 11 L of deionized water were added to a reactor, the temperature was raised to 35 ° C and stirred at a stirring rate of 550 rpm for 45 min, and then 5.5 kg of activated biochar was added to the reactor and mixed, and the solution in the reactor was dripped into 10 L of 4 wt% calcium chloride solution using a syringe pump with a needle diameter of 1.2 mm. The precipitate was filtered, washed with deionized water and freeze-dried to obtain a preparation.

[0066] Embodiment 3:

[0067] A preparation for activating sparingly soluble phosphorus in soil, comprising the following components in parts by weight:

[0068] 6kg activated biochar, 3kg modified starch, 0.4g sodium alginate, 0.5g calcium chloride;

[0069] Activated biochar is produced by the following steps:

[0070] 15 kg of rice straw with a particle size of ≤1 mm and 20 L of deionized water were placed in a reactor, heated to 210 °C for 10 h, filtered after cooling, and the precipitate was washed with deionized water and ethanol in turn until the washing liquid was transparent. Then 500 mL of the mixed bacterial solution was evenly sprayed on the surface of the precipitate and dried at 40 °C to obtain activated biochar.

[0071] The mixed bacterial liquid is prepared by mixing equal volumes of fermentation liquid of Bacillus amyloliquefaciens and fermentation liquid of Bacillus megaterium phosphate-solubilizing;

[0072] The fermentation broth of Bacillus amyloliquefaciens and Bacillus megaterium phosphate-solubilizing was prepared by conventional seed tank expansion culture method, and the number of bacterial species in the prepared fermentation broth was greater than 8x10 8 cfu / mL.

[0073] Oxalic acid corn starch is prepared by the following steps:

[0074] In a reactor, 1.5 kg of oxalic acid was dissolved in 2.5 kg of dimethyl sulfoxide, 3 kg of dry corn starch was added to the reactor, and 30 kg of benzene and 1.5 g of pyridine were added respectively, and the mixture was stirred at 100° C. for 4 hours. After cooling to room temperature, 3 kg of ethanol was added and stirred. The precipitate was filtered and washed with 50 wt % ethanol until the last washing liquid was neutral. The precipitate was dried at 100° C. for 24 hours, and ground through a 100 mesh sieve to obtain oxalic acid corn starch.

[0075] Modified starch is prepared by the following steps:

[0076] 3 kg of oxalate corn starch, 0.8 kg of sodium citrate and 100 g of boric acid were added into a reactor, and 12 L of deionized water was added. The temperature was raised to 50° C., stirred for 20 min, cooled to room temperature, and spray-dried to obtain modified starch.

[0077] A method for preparing a preparation for activating sparingly soluble phosphorus in soil comprises the following steps:

[0078] 3 kg of modified starch, 0.4 kg of sodium alginate and 12 L of deionized water were added to a reactor, the temperature was raised to 40 ° C and stirred at a stirring rate of 600 rpm for 60 min, and then 60 g of activated biochar was added to the reactor and mixed. After that, the solution in the reactor was dripped into 10 L of 5 wt% calcium chloride solution using a syringe pump with a needle diameter of 1.6 mm. The precipitate was filtered, washed with deionized water and freeze-dried to obtain a preparation.

[0079] Sodium alginate, calcium chloride, ethanol, dimethyl sulfoxide, benzene, pyridine, oxalic acid, sodium citrate, and boric acid were purchased from Sigma-Aldrich.

[0080] Application Example 1:

[0081] A method of applying a preparation for activating sparingly soluble phosphorus in soil is:

[0082] The preparation was administered at 25 kg / hm 2 Apply the application amount into the soil at a depth of 5 cm, sprinkle water to make the soil moisture content at a depth of 5 cm reach 30%, and the application is completed.

[0083] The sodium alginate in the preparation can absorb and retain water and has a certain viscosity. It can be used as a binder to form aggregates in the soil, improve soil agglomeration, and increase the adsorption capacity of soil aggregates to insoluble phosphorus. The metal ions of insoluble phosphorus will be adsorbed by the oxalic acid groups and citric acid groups on the surface of the modified starch in the preparation and activated by phosphate-solubilizing bacteria, thereby activating the insoluble phosphorus in the soil and converting the insoluble phosphorus into soluble phosphorus for absorption by plants.

[0084] Application Example 2:

[0085] A method of applying a preparation for activating sparingly soluble phosphorus in soil is:

[0086] The preparation was administered at 35 kg / hm 2 Apply the application amount into the soil at a depth of 7 cm, sprinkle water to make the soil moisture content at a depth of 7 cm reach 35%, and the application is completed.

[0087] Application Example 3:

[0088] A method of applying a preparation for activating sparingly soluble phosphorus in soil is:

[0089] The preparation was administered at 40 kg / hm 2 Apply the application amount into the soil at a depth of 10 cm, sprinkle water to make the soil moisture content at a depth of 10 cm reach 40%, and the application is completed.

[0090] Application example 4:

[0091] A method of applying a preparation for activating sparingly soluble phosphorus in soil may also be:

[0092] Mix the required phosphorus fertilizer with the preparation in a mass ratio of 10:3 and apply it to the soil at a depth of 5 cm. Then sprinkle water to make the soil moisture at a depth of 5 cm reach 30%. The application is completed.

[0093] After the preparation is mixed with phosphate fertilizer, phosphate fertilizer will adhere to the surface of the preparation. After watering, the phosphate liquid after the phosphate fertilizer is dissolved on the surface of the preparation will be adsorbed by the preparation, which reduces the complexation of the quick-acting phosphorus after the phosphate fertilizer is dissolved with metal cations in the soil, and forms aggregates in the soil. The phosphate liquid adsorbed by the preparation slowly releases the phosphate fertilizer under the slow-release effect of sodium alginate, thereby increasing the soluble phosphorus content in the soil after fertilization.

[0094] After the sodium alginate is slowly released, the activated biochar in the preparation and the modified starch on its surface can be dissolved and dispersed in the soil, further adsorbing the insoluble phosphorus in the soil aggregates. Under the action of the phosphate-solubilizing bacteria in the activated biochar, the insoluble phosphorus bound to metal ions is activated and converted into soluble phosphorus. The corn starch in the activated biochar also provides the soil microorganisms with the carbon source required for growth. The activated biochar provides a growth environment for microorganisms and bacteria, and the aggregation of microorganisms further enhances the stability of aggregates in the soil. Sodium alginate forms smaller microspheres under the action of calcium ions in the soil and phosphate fertilizer. Corn starch forms smaller microaggregates after chelating metal ions due to its shorter molecular chain, which is easier to disperse and settle in the soil and has a good activation effect.

[0095] Application Example 5:

[0096] A method of applying a preparation for activating sparingly soluble phosphorus in soil may also be:

[0097] Mix the required phosphorus fertilizer with the preparation in a mass ratio of 10:4 and apply it to the soil at a depth of 7 cm. Then sprinkle water to make the soil moisture at a depth of 7 cm reach 35%, and the application is completed.

[0098] Application Example 6:

[0099] A method of applying a preparation for activating sparingly soluble phosphorus in soil may also be:

[0100] Mix the required phosphorus fertilizer and the preparation in a mass ratio of 10:5 and apply it to the soil at a depth of 10 cm. Then sprinkle water to make the soil moisture at a depth of 10 cm reach 40%, and the application is completed.

[0101] Comparative Example 1:

[0102] The difference from Example 1 is that the modified starch is corn starch.

[0103] Comparative Example 2:

[0104] The difference from Example 1 is that the modified starch is highly carboxylated oxalic acid corn starch.

[0105] A wheat field experiment was conducted in the acidic soil of Nanling County, Wuhu City. The soil was red soil, the wheat variety tested was "Hangmai 2566", the previous crop was corn and soybean, all the straw was returned to the field, and 150kg / hm2 of pure nitrogen was applied to the bottom. 2 , pure phosphorus 80kg / hm 2 , pure potassium 100kg / hm 2, set 1 hectare of soil as a block, take the preparations prepared in Example 1-Example 3 and Comparative Example 1-Comparative Example 2, and apply them to different blocks according to the application methods of Application Example 1-Application Example 3, respectively. The test results of each group of Application Example 1-Application Example 3 are averaged, and an additional blank group (soil) without treatment is set.

[0106] After wheat was harvested, biomass and grain yield were investigated, and wheat yield and plant phosphorus accumulation were analyzed. The method for determining plant phosphorus accumulation was as follows: the plants were washed and dried to constant weight, and then the dry weight was determined. The dried samples were then crushed, and the plants were digested with H2SO4-H2O2. The phosphorus content was determined using a fully automatic continuous flow analyzer. Plant organ phosphorus accumulation = plant organ dry weight × plant organ phosphorus content. The results are shown in Table 1:

[0107] Table 1

[0108] project <![CDATA[Wheat yield (kg / hm 2 )]]> <![CDATA[Phosphorus accumulation (kg / hm 2 )]]> Example 1 6472 33.38 Example 2 6558 34.16 Example 3 6504 33.82 Comparative Example 1 6079 27.25 Comparative Example 2 6125 27.83 Blank Group 5936 25.41

[0109] As can be seen from Table 1, the wheat yield of Examples 1 to 3 of the present invention was increased by 9.1%-10.5% compared with the blank group, and the phosphorus accumulation in the plants was increased by 31.3%-34.4% compared with the blank group, indicating that the preparation of the present invention can well activate the insoluble phosphorus in the soil and convert it into soluble phosphorus to be absorbed and utilized by plants, and significantly increase the yield. Comparative Examples 1 and 2 have weak chelating ability for metal ions and weak activation ability for insoluble phosphorus in the soil, so the yield and phosphorus accumulation are lower than those of Examples 1 to 3.

[0110] An indoor simulation test was conducted with local acidic soil as the research object. The test soil was naturally air-dried, crushed and sieved through a 2 mm sieve. The preparations for activating sparingly soluble phosphorus in the soil in the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 2 were taken, respectively mixed with water-soluble phosphate fertilizers according to the application methods of Application Examples 4 to 6 of the present invention, and then applied to 1 kg of sieved soil. The test results of each group of Application Examples 1 to 3 were averaged, and after being fully mixed, they were placed in an incubator at 28°C, and an additional control group (direct application of phosphate fertilizer to the soil) was set up.

[0111] The soil after 10 days, 30 days and 60 days of cultivation were taken from the soil of Example 1 to Example 3 and Comparative Example 1 to Comparative Example 2 after phosphate fertilizer was applied. The available phosphorus content in the soil was determined using the NY / T1121.7-2014 standard. The results are shown in Table 2:

[0112] Table 2

[0113]

[0114] As can be seen from Table 2, the content of available phosphorus in the soil of Examples 1 to 3 on the 10th day was slightly lower than that of the control group and Comparative Example 2, and slightly higher than that of Comparative Example 1. This is because the phosphate fertilizer applied in the control group was completely dissolved in the soil, resulting in a higher content of available phosphorus in the soil in a short period of time. In Examples 1 to 3, part of the phosphate fertilizer was adsorbed by sodium alginate, resulting in a lower content of available phosphorus in the soil. However, since most of the phosphate fertilizer was still dissolved in the soil, Examples 1 to 3 were slightly lower than the control group. In Comparative Example 1, corn starch was used, which was more effective for metal The ions have no adsorption effect, so that part of the adsorbed phosphate fertilizer is chelated with the metal ions to generate insoluble phosphorus, so the content of available phosphorus is the least. In Comparative Example 2, since the modified starch is highly carboxylated oxalic acid corn starch, although it has a strong adsorption effect on metal ions, it has a strong water absorption capacity, competes with sodium alginate for water molecules, and accelerates the swelling of sodium alginate microspheres, so that the starch emulsion is released into the soil, weakening the slow-release effect of sodium alginate on phosphate fertilizer. Therefore, the available phosphorus content of Comparative Example 2 is slightly higher than that of Examples 1 to 3, and slightly lower than that of the control group;

[0115] The content of available phosphorus in Examples 1 to 3 on the 30th and 60th days was higher than that in the control group and Comparative Examples 1 and 2. The decrease in the available phosphorus content in Comparative Examples 1 and 2 on the 60th day was higher than that on the 30th day, indicating that after the sustained-release effect of sodium alginate weakened over time, the chelating ability of biochar for metal ions gradually weakened, so the content of available phosphorus in the soil gradually decreased. However, under the phosphate solubilization effect of phosphate-solubilizing bacteria, the content of available phosphorus in the soil was slightly higher than that in the control group, indicating that the modified starch of the present invention has a longer-term metal ion chelating ability, and has higher stability to the aggregates in the soil, so that the adsorption effect of the aggregates on insoluble phosphorus is stronger, so more insoluble phosphorus is adsorbed by the aggregates and converted into available phosphorus that can be used by plants under the action of phosphate-solubilizing bacteria. Therefore, the decrease in the available phosphorus content in the soil of Examples 1 to 3 is low, which is consistent with the curve of the amount of phosphate fertilizer required for plant growth, and can well activate the insoluble phosphorus in the soil, providing good phosphate fertilizer soil for crops.

[0116] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0117] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation for activating sparingly soluble phosphorus in soil, characterized in that: It includes the following components by weight: 50-60 parts of activated biochar, 20-30 parts of modified starch, 3-4 parts of sodium alginate, 3-5 parts of calcium chloride; The preparation is prepared by the following method: Sodium alginate and deionized water are added into a reactor to prepare a 3-4 wt% sodium alginate solution, and then modified starch is added and mixed, the reactor is heated to 30-40° C. and stirred at a rate of 500-600 rpm for 30-60 min, and then activated biochar is added into the reactor, stirred and mixed to obtain a mixed dispersion, and the mixed dispersion is dropped into a 3-5 wt% calcium chloride solution prepared by calcium chloride, and the precipitate is filtered, and the precipitate is washed with deionized water and freeze-dried to obtain a preparation; The modified starch is prepared by the following steps: Add oxalate corn starch, sodium citrate and boric acid into a reaction kettle, add deionized water, heat to 40-50°C, stir for 15-20 minutes, cool to room temperature, and spray dry to obtain modified starch; The oxalate corn starch is prepared by the following steps: Dissolve oxalic acid in dimethyl sulfoxide in a reaction kettle, add dry corn starch into the reaction kettle, then add benzene and pyridine respectively, stir and react at 75-100° C. for 2-4 hours, cool to room temperature, add ethanol and stir to obtain a precipitate, filter the precipitate, wash the precipitate with 50wt% ethanol until the last washing liquid is neutral, dry the precipitate at 90-100° C. for 12-24 hours, grind through an 80-100 mesh sieve, and obtain oxalic acid corn starch.

2. A preparation for activating sparingly soluble phosphorus in soil according to claim 1, characterized in that: The activated biochar is prepared by the following steps: placing rice straw with a particle size of ≤1 mm and deionized water in a reactor, heating to 190-210°C for reaction for 8-10 hours, filtering after cooling, washing the precipitate, and then evenly spraying the mixed bacterial liquid on the surface of the precipitate, and drying at 30-40°C to obtain the activated biochar.

3. A preparation for activating sparingly soluble phosphorus in soil according to claim 2, characterized in that: The mixed bacterial liquid is prepared by mixing equal volumes of starch-degrading bacterial fermentation liquid and phosphate-solubilizing microbial fermentation liquid.

4. The preparation for activating sparingly soluble phosphorus in soil according to claim 2, characterized in that: The usage ratio of the rice straw, deionized water and mixed bacterial solution is 100-150 g: 150-200 mL: 4-5 mL.

5. The preparation for activating sparingly soluble phosphorus in soil according to claim 1, characterized in that: The dosage ratio of the oxalate corn starch, sodium citrate, boric acid and deionized water is 20-30 g: 5-8 g: 0.5-1 g: 100-120 mL.

6. The preparation for activating sparingly soluble phosphorus in soil according to claim 1, characterized in that: The mass ratio of the oxalic acid, dimethyl sulfoxide, corn starch, benzene and pyridine is 10-15:20-25:20-30:100-300:0.1-0.

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7. The method for applying a preparation for activating sparingly soluble phosphorus in soil according to claim 1, characterized in that: The application method is: The preparation is administered at 25-40 kg / hm 2 The application amount can be adjusted by mixing the required phosphorus fertilizer with the preparation in a mass ratio of 10:3-5 and applying it into the soil at a depth of 5-10cm. Watering should be carried out so that the soil moisture content at a depth of 5-10cm reaches 30-40%, and the application is completed.

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