Method for improving saline-alkali soil by using organic acid pretreated straw decomposition liquid

Abstract

The application belongs to the technical field of saline-alkali soil improvement, and discloses a method for improving saline-alkali soil by using organic acid pretreated straw decomposition liquid. The application uses a mixed organic acid solution combined with fresh soil solution to pretreat straw, breaks the dense crystalline structure of straw fiber, increases the adhesion capacity of straw to salt ions, and the prepared soluble straw decomposition liquid can increase the activity of soil colloid, promote the release of adsorbed salt ions in the soil, improve the migration capacity of salt ions, and realize efficient removal of salt ions. The prepared pretreated straw material and decomposition liquid are environmentally friendly, non-toxic and harmless, and can be applied to saline-alkali soil improvement, promote the dissolution and infiltration of salt ions in saline-alkali soil, and prevent the surface aggregation of salt ions in the soil surface. The method has the characteristics of low cost, simple operation and obvious effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of saline-alkali soil improvement, and relates to a method for improving saline-alkali soil by using organic acid pretreated straw decomposition liquid. BACKGROUND

[0002] There are about 12 billion mu of saline-alkali land in the world, accounting for 8.7% of the land area. Among them, about 500 million mu of saline-alkali land can be cultivated in China. The development and utilization of saline-alkali land is of great significance to guarantee food and ecological safety in China. In recent years, various remediation technologies have been developed for the remediation and management of saline-alkali land. Patent CN202111294239.0 discloses a method for preparing a saline-alkali soil conditioner by fermenting and adjusting phosphogypsum, which adjusts the water content by using phosphogypsum, grinds and adds biological nutrients such as chicken manure, fully mixes, and then grinds and ferments to prepare a saline-alkali soil conditioner, which can effectively reduce the salt content and pH value of saline-alkali soil and alleviate the influence of soil salt on crop growth. Patent CN202311205736.8 discloses a method for improving saline-alkali land by using straw and phosphorus-solubilizing microorganisms, which adds straw and inoculates phosphorus-solubilizing microorganisms in saline-alkali land to improve the saline-alkali soil in Tianjin area. Patent CN202310983130.0 discloses a saline-alkali land conditioner and its preparation and use method, which uses a biological source humic acid grafted with an acrylic acid polymer and adds guanidine sulfate or guanidine carbonate, pyridine chloride, cetyl diethyl ammonium bromide, etc. to prepare a straw-based composite salt-absorbing and water-retaining material, which can reduce the salt content of the saline-alkali surface layer, improve the salt-tolerance and water-retention of crops, and reduce the stress of saline-alkali on crops. Patent CN202210386125.7 provides a saline-alkali land improvement calcium chloride-loaded modified biochar composite material and its preparation method, which collects plant raw materials, washes and dries them, limits oxygen pyrolysis at 450℃ for 1h to obtain original biochar, then mixes the original biochar with a calcium chloride solution at a certain ratio, dries, and limits oxygen pyrolysis at 200℃ to prepare a biochar-loaded calcium chloride-modified biochar composite material, which can effectively adsorb salt in the soil and reduce the migration ability of soil salt ions. Although the above materials can fix soil salt ions and reduce the risk of salt damage to crops, they also have the risk of high preparation cost and secondary pollution.

[0003] The present application uses cheap biomass raw materials, modifies the straw by using environmentally friendly organic acid, and mixes fresh soil extract liquid to prepare modified straw material and straw decomposition liquid after simple fermentation. The salt ions in the saline-alkali soil are washed according to the appropriate amount, the content of the surface layer salt is reduced, the surface layer salt is prevented from re-aggregating, and the occurrence of crop salt damage is alleviated. The present method has low preparation cost, simple application method, and good popularization and utilization prospect. SUMMARY

[0004] The application establishes a method for improving saline-alkali soil by using organic acid pretreated straw decomposition liquid around the problem of soil salinization. The method uses cheap and easily available straw, and the straw is pretreated by organic acid mixed solution and fresh soil solution in sequence, so as to break the dense crystalline structure of straw fiber, increase the specific surface area of straw, and enhance the adhesion capacity of straw fiber to salt ions. At the same time, the small molecule soluble substances released in the straw decomposition process can improve the buffer capacity of soil colloids, promote the dissolution and downward migration of soil salt ions, reduce the residence time of soil surface layer salt ions, and hinder the surface accumulation of salt in saline-alkali soil.

[0005] The technical scheme of the application:

[0006] A method for improving saline-alkali soil by using organic acid pretreated straw decomposition liquid, the steps are as follows:

[0007] (1) Pretreatment of straw decomposition by organic acid solution

[0008] Fresh straw is collected from farmland, naturally air-dried, crushed into solid small particles, and soaked in organic acid mixed aqueous solution at 20-40℃ for 1-2d according to the solid-liquid ratio of 1:20 (straw mass g and solution volume ml); fresh soil is taken from the surface layer of 1-5cm of farmland, mixed thoroughly according to the water-soil ratio of 1:5 (water volume ml and soil mass g), and centrifuged at 3000r / min for 1-5min; the soil supernatant is taken, and the soil supernatant is added to the reaction container according to 10-20% of the mass of the straw after initial natural air-drying, and 0.1-2% tartaric acid and 0.1-5% potassium pyroantimonate of the initial straw mass are added, and the decomposition reaction is continued at 20-40℃ for 3-5d, then solid-liquid separation is carried out, the straw solid is washed clean with clean water, and is fully dried in a 60-80℃ air-drying oven for 24-36h, then is crushed to obtain pretreated straw solid powder (a), which is packed in a self-sealing bag for standby; the straw decomposition liquid obtained by the above separation is filtered twice to obtain filtered straw decomposition liquid (b), which is packed in a brown glass bottle or opaque plastic bottle for standby;

[0009] (2) Conditions for washing and improving salt ions in saline-alkali soil

[0010] According to the pretreated straw solid powder (a) obtained in step (1) 0.5-2.0 kg per square meter of land, the pretreated straw solid powder is evenly paved to 10 cm below the surface layer of saline soil, and then the pretreated cotton straw solid powder is evenly covered with soil; the straw decomposition liquid (b) obtained in step (1) is applied to the saline soil in need of repair by slow irrigation or spraying, 1-5 kg of straw decomposition liquid per square meter of land per day, 1-2 times a day, and the whole cycle is performed for 3-7 days, finally, the pretreated straw solid powder (a) is evenly covered on the surface layer of the saline soil in an amount of 0.1-2.0 kg per square meter, to prevent water evaporation from the surface layer and play a role in water and fertilizer conservation.

[0011] The straw includes cotton, corn and wheat.

[0012] The mass ratio of organic acid in the organic acid mixed aqueous solution is 1-5%, and the mass ratio of ferrous sulfate is 0.1-0.2%.

[0013] The organic acid includes one or more than two kinds of acetic acid, oxalic acid, fumaric acid and citric acid.

[0014] The soil type includes black calcareous soil, chao soil, brown soil, sandy soil and clay.

[0015] The application has the following beneficial effects: the application uses the organic acid mixed solution combined with fresh soil solution to pretreat the straw, breaks the dense crystal structure of the straw fiber, increases the adhesion capacity of the straw to salt ions, and the prepared soluble straw decomposition liquid can increase the activity of soil colloids, promote the release of adsorbed salt ions in the soil, and improve the migration capacity of salt ions, so that the salt ions can be removed efficiently, the prepared pretreated straw material and decomposition liquid are environmentally friendly and non-toxic and harmless, and can be applied to saline-alkali soil improvement, promote the dissolution and downward infiltration of salt ions in the saline-alkali soil, and prevent the surface aggregation of salt ions in the soil, and the method has the characteristics of low cost, simple operation and obvious effect. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the salt absorption performance of the organic acid pretreated cotton straw material.

[0017] Figure 2 is the infrared spectrum of the organic acid pretreated cotton straw material.

[0018] Figure 3 is the scanning electron microscope image of the organic acid pretreated cotton straw material, wherein (a) is the original straw, and (b) is the straw pretreated by oxalic acid solution.

[0019] Figure 4 is the effect of the pretreated cotton straw material dosage on the salt content of saline-alkali soil.

[0020] Figure 5 Effect of pretreated cotton stalk decomposition liquid on salt content of saline-alkali soil. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and technical solutions.

[0022] Example 1 Preparation and performance comparison of pretreated cotton stalk decomposition liquid of different sources of organic acid solution

[0023] The discarded cotton stalks were collected from the cotton field, naturally air-dried, and crushed into small particles with a side grass machine. 10 g of cotton stalks were weighed and added to a 500 mL glass beaker. Organic acid aqueous solutions were prepared according to the proportion of 1% of the solution mass of acetic acid, oxalic acid, citric acid, etc. The mass of ferrous sulfate was controlled at 0.1% of the solution mass. 200 mL of different sources of organic acid solution was poured into the glass beaker and placed in a constant temperature incubator with a temperature of 25°C. Fresh soil samples of 10 g were taken from the cotton field where the cotton stalks were collected, placed in the beaker, mixed with 50 mL of water, and centrifuged at 3000 r / min for 5 min. 1 mL of soil supernatant was taken and added to the above-mentioned reaction glass beaker. Tartaric acid 0.02 g and potassium pyroantimonate 0.01 g were added, stirred thoroughly, and placed in a constant temperature incubator with a temperature of 25°C. The decomposition reaction was continued for 3 days. After the reaction was completed, solid-liquid separation was performed by suction filtration. The modified cotton stalk solid obtained from the upper layer was washed with water for 3 times to remove the adhered solid particles, and was dried thoroughly in a 80°C air-drying oven for 24 h. The pretreated cotton stalk solid powder was obtained by crushing with a pulverizer and was packed in a self-sealing bag for later use. The decomposition liquid obtained from the lower layer was packed in a brown glass bottle after being filtered twice for later use. Sequential batch adsorption experiments were conducted to test the salt adsorption capacity of the cotton stalk solid powder under different pretreatment conditions of organic acid. As shown in FIG. 1, the salt adsorption capacity of the pretreated cotton stalk solid powder under different organic acid solution treatments was 4.53 mg / kg (acetic acid solution), 4.98 mg / kg (oxalic acid solution), and 5.76 mg / kg (citric acid solution), respectively. Compared with the untreated cotton stalk, the salt adsorption capacity of the material was increased by 28.7%-63.6%. Figure 1 As shown in FIG. 2, the absorption peak of the carbonyl functional group of the cotton stalk material treated with organic acid was weakened (FIG. 3), and the number of pores of the cotton stalk material pretreated with acetic acid was increased (FIG. 4). The elemental analysis results showed that the modified material loaded with iron elements, and these structural changes were beneficial to improve the salt adsorption capacity of the modified cotton stalk material. Figure 2 Figure 3

[0024] Example 2 Application method and effect of pretreated cotton stalk material

[0025] ​​Modified cotton stalk material and decomposition solution were prepared according to the process in Example 1, wherein the amounts of acetic acid and oxalic acid were both 1%, ferrous sulfate was controlled at 0.2% of the solution mass, tartaric acid was 0.04 g, potassium pyroantimonate was 0.02 g, the reaction temperature was controlled at 25℃, and other conditions remained unchanged. The prepared modified cotton stalk material and decomposition solution were stored for later use. The pretreated cotton stalk solid powder prepared above was spread evenly to 10 cm below the surface of the saline-alkali soil, and evenly sprinkled on the surface of the saline-alkali soil at amounts of 0 kg, 0.5 kg, 1.0 kg, and 2.0 kg of pretreated cotton stalk solid powder per square meter, respectively, with a plot area of ​​1 m². 2 The initial total salt content in the soil was 8.6 g / kg. The obtained cotton stalk decomposition solution was used to slowly irrigate the saline-alkali soil. 3 kg of cotton stalk decomposition solution was applied per square meter per day, twice a day, for a total of 5 days. Each group had 3 replicates. The total salt content in the soil layer covering the cotton stalk solid material was then tested. The results are attached. Figure 4 As shown, the total salt content in the soil gradually decreased from 8.6 g / kg to 3.1 g / kg, a reduction of 54.4%, as the amount of cotton stalk solid powder material used increased.

[0026] Example 3: Application method and effects of organic acid decomposition solution

[0027] Modified cotton stalk material and straw decomposition liquid were prepared according to the process in Example 1, wherein the amount of oxalic acid was 2%, the mass of ferrous sulfate was controlled at 0.2% of the solution mass, tartaric acid was 0.04 g, potassium pyroantimonate was 0.02 g, the reaction temperature was controlled at 25℃, and other conditions remained unchanged. The prepared modified cotton stalk material and decomposition liquid were stored for later use. The pretreated cotton stalk solid powder prepared above was spread evenly to 10 cm below the surface of the saline-alkali soil, and 1.0 kg of pretreated cotton stalk solid powder per square meter was evenly sprinkled on the surface of the saline-alkali soil, with a plot area of ​​1 m². 2 The initial total salt content in the soil was 8.6 g / kg. The obtained cotton stalk decomposition solution was used to slowly leach the saline-alkali soil. The leaching was carried out at different rates: 0 kg, 1 kg, 2 kg, and 4 kg of cotton stalk decomposition solution per square meter per day, once a day for 3 days, with 3 replicates per group. The total salt content in the soil layer covering the cotton stalk solid material was then tested. The results are shown in the attached figure. Figure 5 As shown, with the increase in the amount of cotton stalk decomposition liquid, the total salt content in the soil decreased from 7.9 g / kg to 2.7 g / kg, a reduction of 65.8%.

Claims

1. A method for improving saline-alkali soil by pretreating straw decomposition liquid with organic acid, characterized in that, The steps are as follows: (1) Decomposition of straw by pretreatment with organic acid solution Fresh straw was collected from farmland, naturally air-dried, and then crushed into small solid particles. The straw was soaked in a mixed aqueous solution of organic acid at a solid-liquid ratio of 1:20 (g straw mass to ml solution volume) for 1-2 days at 20-40℃. Fresh soil from 1-5 cm below the surface of the farmland was taken and thoroughly mixed with water at a soil-water ratio of 1:5 (ml water volume to g soil mass). The mixture was then centrifuged at 3000 rpm for 1-5 minutes. The soil supernatant was collected and added to the reaction vessel at 10-20% of the initial air-dried straw mass. Then, add 0.1-2% tartaric acid and 0.1-5% potassium pyroantimonate by the initial straw mass, and continue the decomposition reaction at 20-40℃ for 3-5 days. Then, perform solid-liquid separation. Wash the straw solid with clean water, dry it thoroughly in a forced-air drying oven at 60-80℃ for 24-36 hours, and pulverize it to obtain pretreated straw solid powder (a), which is then packed into a self-sealing bag for later use. The straw decomposition liquid obtained above is filtered twice to obtain filtered straw decomposition liquid (b), which is then packed into a brown glass bottle or an opaque plastic bottle for later use. (2) Conditions for washing and improving saline-alkali soil with salt ions Apply 0.5-2.0 kg of pretreated straw solid powder (a) obtained in step (1) per square meter of land. Spread the pretreated straw solid powder evenly to 10 cm below the surface of the saline-alkali soil. Then cover the pretreated straw solid powder evenly with soil. Apply the straw decomposition liquid (b) obtained in step (1) to the saline-alkali soil that needs to be repaired by slow irrigation or spraying. Apply 1-5 kg ​​of straw decomposition liquid per square meter of land per day, 1-2 times a day, for a total cycle of 3-7 days. Finally, apply 0.1-2.0 kg of pretreated straw solid powder (a) evenly to the surface of the saline-alkali soil to prevent surface moisture evaporation and play a role in water and fertilizer retention.

2. The method for improving saline-alkali soil by pretreating straw decomposition liquid with organic acid according to claim 1, characterized in that, The straw mentioned includes cotton, corn, and wheat.

3. The method for improving saline-alkali soil by pretreating straw decomposition liquid with organic acid according to claim 1, characterized in that, The organic acid mixed aqueous solution contains 1-5% organic acid by mass and 0.1-0.2% ferrous sulfate by mass.

4. The method for improving saline-alkali soil by pretreating straw decomposition liquid with organic acid according to claim 3, characterized in that, The organic acids mentioned include one or more of acetic acid, oxalic acid, fumaric acid, citric acid, and salicylic acid.

5. The method for improving saline-alkali soil by pretreating straw decomposition liquid with organic acid according to claim 3, characterized in that, The soil types mentioned include black calcareous soil, alluvial soil, brown soil, sandy soil, and clay soil.

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