Method for improving slightly salinized soil and use thereof

Abstract

The application belongs to the technical field of soil improvement, and particularly relates to a method for improving slightly salinized soil and application thereof. The iron modified bacteria-straw hydrothermal carbon can remove the adsorbed sodium ions in the slightly salinized soil through displacement; meanwhile, the bacteria-straw hydrothermal carbon can supplement the organic carbon content in the soil, improve the soil structure through soil particle combination, reduce the soil bulk density, and thus improve the soil environmental conditions, so as to achieve the effect of improving the slightly salinized soil. On this basis, the bacteria-straw co-fermentation is added to further improve the soil structure, reduce the soil bulk density, form humus in the soil, and be beneficial to the improvement of the soil texture. On the basis of the bacteria-straw co-fermentation, the bacteria-straw based solid acid is added to neutralize the alkaline substances in the soil, further reduce the pH of the soil, realize the multi-stage utilization of the bacteria-straw, and make the improved soil be able to be used efficiently, especially as rice seedling soil, promote the rapid growth of rice seedlings, and improve the rice yield.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a method for improving slightly saline-alkali soil and its application. Background Technology

[0002] Saline-alkali soils are characterized by poor physical and chemical properties, soil compaction, low nutrient availability, low organic matter content, and poor permeability, which seriously affect crop growth. Current production practices show that planting rice in saline-alkali soils is an important way to improve and utilize them.

[0003] Rice cultivation requires a large amount of rice seedling bed soil for raising seedlings. In the past, rice seedling bed soil was mostly taken from riverbed soil or black soil arable land. However, with the environmental damage caused by soil extraction, the implementation of black soil protection policies, and the large expenses incurred in the production and transportation of seedling bed soil, there is an urgent need to develop new alternative seedling substrates and to use improved slightly saline-alkali soil for rice seedling raising.

[0004] Currently, the main approach in this field is to improve saline-alkali soils by adjusting the acidity with concentrated sulfuric acid, adding highly acidic organic materials such as furfural, agricultural and forestry waste, and gypsum, in order to obtain slightly saline-alkali soils suitable for rice seedling cultivation. However, due to the low microbial activity, poor structure, high pH value, and high salt content in slightly saline-alkali soils, coupled with the simplistic improvement process of traditional techniques, the overall soil quality cannot meet the requirements for rice seedling cultivation, resulting in poor seedling quality that cannot grow in saline-alkali soils, thus affecting yield. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving slightly saline-alkali soil and its application. The method can rapidly reduce alkali and salt, improve soil structure, activate and maintain the nutrients required for plant growth, and increase organic carbon in the soil, thereby improving slightly saline-alkali soil.

[0006] This invention provides a method for improving slightly saline-alkali soil, comprising the following steps: applying iron-modified biochar hydrothermal char at a mass ratio of 2% to 6% into slightly saline-alkali soil, followed by soaking and washing the soil to obtain iron-modified biochar hydrothermal char-improved soil.

[0007] The iron-modified bacterial bran hydrothermal char comprises bacterial bran hydrothermal char and iron atoms loaded on the bacterial bran hydrothermal char.

[0008] Preferably, the loading of iron atoms in the bacterial bran hydrothermal charcoal is 19.6% to 28%.

[0009] Preferably, the soil is washed in the field 3 to 4 times.

[0010] Preferably, the method further includes: mixing the mushroom residue with the iron-modified mushroom residue hydrothermal char soil amendment at a mass ratio of 20% to 30%, and fermenting and culturing it under a moisture content of 50% to 60% to obtain mushroom residue co-fermented soil amendment.

[0011] Preferably, the fermentation culture time is 30 to 40 days and the temperature is 15 to 25°C.

[0012] Preferably, the method further includes: mixing the bacterial bran-based solid acid with the bacterial bran at a mass ratio of 5% to 10% to co-ferment and improve the soil, thereby obtaining mildly salinized improved soil;

[0013] The preparation method of the bacterial bran-based solid acid includes: mixing bacterial bran with concentrated sulfuric acid, carbonizing, and drying to obtain the bacterial bran-based solid acid.

[0014] Preferably, the concentrated sulfuric acid has a mass fraction of 98%.

[0015] Preferably, the mass ratio of the bacterial bran to the volume ratio of the concentrated sulfuric acid is 1g:(0.5-5)mL.

[0016] The present invention also provides improved soil obtained by the method described in the above technical solution, wherein the pH value of the improved soil is 5.20 to 7.50.

[0017] This invention also provides the application of the improved soil described in the above technical solution as rice seedbed soil.

[0018] Beneficial effects:

[0019] This invention provides a method for improving slightly saline-alkali soil, comprising the following steps: applying iron-modified biochar hydrothermal char at a mass ratio of 2% to 6% to the slightly saline-alkali soil, followed by soaking and washing the soil to obtain iron-modified biochar hydrothermal char-improved soil; the iron-modified biochar hydrothermal char comprises biochar hydrothermal char and iron atoms loaded on the biochar hydrothermal char. The iron-modified biochar hydrothermal char of this invention can remove adsorbed sodium ions in slightly saline-alkali soil through displacement, and reduce carbonate ions through carboxyl and hydroxyl groups; simultaneously, the biochar hydrothermal char can replenish the organic carbon content in the soil, improve soil structure through soil particle binding, activate and maintain nutrients required for plant growth, reduce soil bulk density, thereby improving soil environmental conditions and achieving the effect of improving slightly saline-alkali soil.

[0020] Based on the improvement of slightly saline-alkali soil by iron-modified biochar, biochar is added to provide an environment conducive to microbial growth. In turn, the co-fermentation of biochar reduces the soil bulk density and forms humus in the soil, which is beneficial to the improvement of soil texture.

[0021] Based on the co-fermentation of inoculum residue, inoculum residue-based solid acid is added to neutralize alkaline substances in the soil, including carbonate and bicarbonate ions, further reducing the soil pH and realizing the multi-level utilization of inoculum residue. This allows the improved soil to be used efficiently, especially as rice seedling soil, promoting the rapid growth of rice seedlings and increasing rice yield. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0023] Figure 1 This is a scanning electron microscope image of the iron-modified bacterial residue hydrothermal char from Example 1;

[0024] Figure 2 This is a diagram illustrating the effect of iron-modified bacterial residue hydrothermal char in reducing the pH of mildly saline-alkali soil in Example 1.

[0025] Figure 3 The image shows the effect of iron-modified bacterial residue hydrothermal char on sodium ion removal in mildly saline-alkali soil in Example 1.

[0026] Figure 4 This is a diagram illustrating the effect of iron-modified bacterial residue hydrothermal char on organic carbon in mildly saline-alkali soil in Example 1.

[0027] Figure 5 This is a diagram illustrating the effect of iron-modified bacterial residue hydrothermal char on phosphorus in mildly saline-alkali soil in Example 1.

[0028] Figure 6 This is a graph showing the effect of iron-modified bacterial residue hydrothermal char on the electrical conductivity of mildly saline-alkali soil in Example 1.

[0029] Figure 7 This is a graph showing the effect of co-fermentation of bacterial residues on the particle size distribution of water-stable aggregates in Example 2;

[0030] Figure 8 This is a visual representation of the bacterial bran-based solid acid prepared in Example 3. Detailed Implementation

[0031] This invention provides a method for improving slightly saline-alkali soil, characterized by the following steps: applying iron-modified biochar hydrothermal char at a mass ratio of 2% to 6% to the slightly saline-alkali soil, followed by soaking and washing the soil to obtain iron-modified biochar hydrothermal char-improved soil; the iron-modified biochar hydrothermal char comprises biochar hydrothermal char and iron atoms loaded on the biochar hydrothermal char.

[0032] The pH value of the slightly saline-alkali soil described in this invention is preferably 8.5 to 9.0, and the total salt content is preferably 0.1% to 0.2%.

[0033] The iron-modified biomass hydrothermal char of this invention preferably comprises biomass hydrothermal char and iron atoms loaded in the biomass hydrothermal char. The loading of iron atoms in the biomass hydrothermal char is preferably 19.6% to 28%, more preferably 28%, that is, 4.9 to 7g of iron atoms are loaded per 25g of biomass hydrothermal char, more preferably 7g of iron atoms are loaded per 25g of biomass hydrothermal char. The iron-modified biomass hydrothermal char of this invention has an unevenly distributed porous structure and large pores on its surface, which has strong ion adsorption and exchange effects.

[0034] The preferred method for preparing iron-modified bacterial residue hydrothermal char of the present invention includes: mixing bacterial residue with ferric sulfate solution and then carrying out a hydrothermal carbonization reaction to obtain the carbonization product;

[0035] The carbonized product is filtered, and the resulting solid product is dried to obtain the iron-modified bacterial bran hydrothermal carbon.

[0036] In this invention, the mushroom residue is preferably crushed and sieved to obtain mushroom residue granules. The mushroom residue granules are preferably the undersize material after passing through a 100-mesh sieve, meaning the particle size of the mushroom residue granules is preferably ≤100 mesh, more preferably 100 mesh.

[0037] After obtaining the mushroom residue granules, the present invention preferably mixes the mushroom residue granules with ferric sulfate solution for hydrothermal carbonization to obtain carbonized products. The mushroom residue of the present invention preferably includes *Auricularia auricula-judae* mushroom residue, which is waste material from the cultivation of fungi such as *Auricularia auricula-judae* using sawdust as the main raw material. The mass ratio of the mushroom residue granules to the ferric sulfate solution of the present invention is preferably 0.5–0.71, more preferably 0.5. The present invention preferably conducts the hydrothermal carbonization reaction in a hydrothermal reactor. The specifications and source of the hydrothermal reactor are not particularly limited; commercially available hydrothermal reactors in the art are acceptable. The temperature of the hydrothermal carbonization reaction of the present invention is preferably 180–220°C, more preferably 180°C; the time is preferably 0.5–4 hours, more preferably 4 hours. During the hydrothermal carbonization process of the present invention, the -OH groups on the surface of the hydrothermal carbon can react with Fe... 3+ Complexation occurs, allowing Fe to 3+ It is loaded on the surface of hydrothermal carbon in the form of oxides, and thus exists in the form of iron atoms.

[0038] After obtaining the carbonized product, the present invention preferably filters the carbonized product and dries the resulting solid product to obtain the iron-modified bacterial bran hydrothermal carbon. The preferred flow rate of the water pump used for filtration is 40–60 L / min, more preferably 60 L / min; the preferred vacuum degree is 0.05–0.098 MPa, more preferably 0.098 MPa. The preferred drying temperature is 75–85°C, more preferably 75°C; the preferred drying time is 12–18 h, more preferably 12 h.

[0039] After obtaining the iron-modified biochar, the present invention applies the iron-modified biochar to slightly saline-alkali soil at a mass ratio of 2% to 6%, followed by soaking and washing the soil. The preferred mass ratio of the iron-modified biochar is 2% to 4%, more preferably 2%. The present invention preferably mixes the modified biochar and the slightly saline-alkali soil thoroughly and evenly. The soaking and washing process is preferably performed 3 to 4 times, more preferably 4 times. Specifically, the mixture of iron-modified biochar and slightly saline-alkali soil is irrigated until saturated, and after the moisture content drops to 40%, water is added again until saturated, for a total of 3 to 4 soaking and washing processes.

[0040] After soaking and washing the soil, the present invention preferably removes the covering water to obtain iron-modified bacterial residue hydrothermal char for soil improvement. The soil improved by the iron-modified bacterial residue hydrothermal char of the present invention has a pH value reduced to below 7.5, and the sodium ion dissolution rate reaches 1491.35–1831.43 mg / kg. The method of improving slightly saline-alkali soil with iron-modified bacterial residue hydrothermal char of the present invention can effectively reduce the soil pH value, promote the leaching of sodium ions, and effectively slow down the loss of organic carbon and phosphorus in slightly saline-alkali soil.

[0041] The iron-modified biochar of this invention can remove adsorbed sodium ions in mildly saline-alkali soil through iron displacement and reduce carbonate ions through carboxyl and hydroxyl groups. At the same time, the biochar can replenish the organic carbon content in the soil and reduce the soil bulk density, thereby improving soil environmental conditions and achieving the effect of improving mildly saline-alkali soil.

[0042] After obtaining the iron-modified bacterial residue hydrothermal char soil amendment, the present invention preferably further includes further amendment of the iron-modified bacterial residue hydrothermal char soil amendment, preferably including:

[0043] The inoculum residue is mixed with the iron-modified inoculum residue hydrothermal char soil at a mass ratio of 20% to 30%, and fermented under conditions of 50% to 60% moisture content to obtain inoculum residue co-fermented soil.

[0044] The preferred mass of the inoculum residue in this invention is 20%–25% of the mass of the iron-modified inoculum residue hydrothermal char used to improve the soil, more preferably 25%. The preferred fermentation temperature is 15–25°C, more preferably 20°C; the preferred fermentation time is 30–40 days, more preferably 30 days. The preferred inoculum residue is inoculum residue particles that have been crushed through a 2mm sieve. The method of mixing and fermenting the iron-modified inoculum residue hydrothermal char used to improve the soil with the inoculum residue in this invention can effectively reduce the soil bulk density, increase the organic matter content in the soil, and further reduce the soil pH value, specifically preferably to 6.96–7.32.

[0045] The inoculum residue described in this invention can provide environmental conditions conducive to microbial growth, reduce soil bulk density, form humus in the soil, improve soil texture, and improve soil structure. The inoculum residue-based solid acid described in this invention can neutralize alkaline substances in the soil, including carbonate and bicarbonate ions, further reducing the soil pH and enabling the improved soil to be used efficiently.

[0046] After obtaining the soil improved by co-fermentation of the bacterial residue, the present invention preferably further improves the soil improved by co-fermentation of the bacterial residue, specifically preferably by mixing the bacterial residue-based solid acid with the soil improved by co-fermentation of the bacterial residue at a mass ratio of 5% to 10% to obtain mildly salinized improved soil.

[0047] The preparation method of the bacterial bran-based solid acid of the present invention includes: mixing bacterial bran with concentrated sulfuric acid and drying to obtain the bacterial bran-based solid acid.

[0048] The preferred method for preparing the bacterial bran-based solid acid of the present invention includes: mixing bacterial bran with concentrated sulfuric acid and drying to obtain the bacterial bran-based solid acid.

[0049] In this invention, the mushroom residue is preferably crushed and sieved to obtain mushroom residue granules. The particle size of the mushroom residue granules in this invention is preferably the same as that in the above-described technical solutions, and will not be repeated here.

[0050] After obtaining the mushroom bran granules, the present invention preferably mixes the mushroom bran granules with concentrated sulfuric acid for carbonization and drying to obtain the mushroom bran-based solid acid. The concentrated sulfuric acid in the present invention preferably has a mass fraction of 98%; the mass ratio of the mushroom bran granules to the volume of the concentrated sulfuric acid is preferably 1 g:(0.5-5) mL. The drying process in the present invention is preferably natural air drying, and the drying temperature is preferably room temperature. The present invention achieves thorough and uniform carbonization by mixing the mushroom bran with concentrated sulfuric acid.

[0051] The preferred mass of the bacterial bran-based solid acid in this invention is 1-10% of the amount of the bacterial bran-based solid acid used in the soil improvement process. Preferably, after mixing, the mixed soil is moistened with water for 3 days to stabilize soil properties. This water moistening ensures the mixed soil maintains a moisture content of approximately 60%. By mixing the bacterial bran-based solid acid with the soil improved through bacterial bran co-fermentation, this invention can lower the pH value of the soil to 5.20-6.56, while simultaneously promoting rice growth. Therefore, the mildly saline-alkali improved soil obtained using the above-described method also falls within the scope of protection of this invention.

[0052] This invention improves mildly salinized soil through a phased process. Specifically, firstly, iron-modified biochar is used to remove and replace sodium ions in the mildly salinized soil, replenishing the organic carbon content. This improves soil structure and reduces soil bulk density through soil particle bonding, thereby improving soil environmental conditions. Secondly, biochar is added to provide favorable conditions for microbial growth, further improving soil structure and reducing bulk density through fermentation, forming humus and improving soil texture. Thirdly, biochar-based solid acid is added to neutralize alkaline substances in the soil, including carbonate and bicarbonate ions, further reducing the soil pH. This allows the improved soil to be used efficiently, especially as rice seedling soil, promoting rapid rice seedling growth and increasing rice yield. This multi-stage utilization of biochar simultaneously improves mildly salinized soil.

[0053] Based on the above advantages, this invention also provides the application of the method described in the above technical solution in rice seedling cultivation. Using the iron-modified biochar hydrothermal char soil, biochar co-fermentation soil, or slightly saline-alkali soil obtained by the method of this invention as rice seedbed soil for rice seedling cultivation can eliminate the harm of salinity to seedlings, activate and maintain the nutrients needed for plant growth, promote rapid seedling growth, and the high content of carbonized substances can reduce problems such as frost damage caused by sudden weather changes during rice seedling cultivation. While protecting soil resources, including black soil, it efficiently utilizes slightly saline-alkali soil, showing great application potential in improving rice yield and quality, especially for slightly saline-alkali soil. This invention does not specifically limit the specific method of rice seedling cultivation; any scheme using the iron-modified biochar hydrothermal char soil, biochar co-fermentation soil, or slightly saline-alkali soil improved by this invention for rice seedling cultivation falls within the protection scope of this invention.

[0054] To further illustrate the present invention, the technical effects provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] The preparation method of iron-modified bacterial residue hydrothermal charcoal and its application in improving slightly saline-alkali soil are as follows:

[0057] 1. The mushroom substrate (from the Engineering Center for Edible and Medicinal Fungi of the Ministry of Education, Jilin Agricultural University) was pulverized and passed through a 100-mesh sieve. 50g of the pulverized substrate was placed in a high-pressure reactor. 500mL of 0.5mol / L ferric sulfate solution was thoroughly mixed with the mushroom substrate powder and poured into a hydrothermal reactor. The reactor was sealed and placed in an oven for hydrothermal carbonization at 180°C for 4 hours. After the reaction, the carbonized product in the reactor was removed and filtered. The resulting solid product was dried in an oven at 75°C for 12 hours. After drying, it was ground and passed through a 100-mesh sieve to obtain iron-modified mushroom substrate hydrothermal carbon.

[0058] The obtained iron-modified bacterial residue hydrothermal char was analyzed by scanning electron microscopy, and the results are as follows: Figure 1 As shown; by Figure 1 It can be concluded that the surface of iron-modified bacterial bran hydrothermal char has an uneven porous structure and large pores.

[0059] The pH value and yield of iron-modified mushroom residue hydrothermal char were determined. The results showed that the pH value of iron-modified mushroom residue hydrothermal char was 2.43 and the yield was 60.5%, where the yield = mass of dried hydrothermal char / mass of mushroom residue used to prepare hydrothermal char.

[0060] 2. The iron-modified biochar prepared in step 1 was added to 200g of slightly saline-alkali soil at mass ratios of 2%, 4%, and 6% respectively (the pH value of the slightly saline-alkali soil was 8.5, the total salt content was 0.12%, and it was collected from Qian'an County, Songyuan City, Jilin Province). After thorough mixing, the mixture was placed into a culture pot. At the same time, a control treatment without any addition was set up, that is, the amount of iron-modified biochar added was 0.

[0061] First, slowly add 400mL of distilled water multiple times to gradually saturate the soil. Then, add 100mL of distilled water each time to soak the soil, for a total of four times. Collect the topsoil and allow the soaked soil to air dry naturally to obtain iron-modified bacterial residue hydrothermal char soil. The air-dried soil was used for soil index determination, specifically including pH value, sodium ion dissolution, organic carbon loss, phosphorus loss, and soil conductivity. The determination of soil pH value, conductivity, and sodium and phosphorus content in the washing solution was based on the method described in "Soil Agricultural Chemical Analysis Methods" by Lu Rukun, China Agricultural Science and Technology Press, 2000. The method for determining the organic carbon content in the washing solution was as follows: the collected washing solution was filtered through a 0.45µm filter membrane and then measured using a total organic carbon analyzer. The results for pH value, sodium ion dissolution, organic carbon loss, phosphorus loss, and soil conductivity for each group are shown below. Figures 2-6 As shown, Figures 2-6 The iron-modified hydrothermal carbon mentioned refers to iron-modified bacterial bran hydrothermal carbon.

[0062] Depend on Figure 2It can be concluded that the pH of the soil after soaking in the control treatment decreased to 8.31, while the pH of the soil after soaking with 2%, 4%, and 6% iron-modified bacterial residue hydrothermal char decreased to 7.50, 7.15, and 6.94, respectively, showing a very significant decrease.

[0063] Depend on Figure 3 It can be concluded that the sodium ion leaching amount per kilogram of soil in the control treatment was 1206.3 mg, while the sodium ion leaching amounts per kilogram of slightly saline-alkali soil in the treatments with 2%, 4%, and 6% iron-modified hydrothermal char were 1491.35 mg, 1773.25 mg, and 1831.43 mg, respectively, showing a significant increase. This indicates that the iron-modified biochar prepared in step 1 can rapidly and effectively reduce soil pH and promote the leaching of sodium ions.

[0064] Depend on Figure 4 It can be concluded that: after soaking and washing the soil in the control treatment, the loss of organic carbon per kilogram of soil was 1120.5 mg. In the slightly saline-alkali soil after water washing with 2%, 4%, and 6% iron-modified bacterial residue hydrothermal carbon, the leaching of organic carbon per kilogram of soil was 776.05 mg, 582.2 mg, and 505.84 mg, respectively, showing a significant decrease.

[0065] Depend on Figure 5 It can be concluded that: the phosphorus loss per kilogram of soil in the control treatment was 8.63 mg; the phosphorus leaching losses per kilogram of soil in the treatments with the addition of 2%, 4%, and 6% iron-modified hydrothermal carbon were 6.03 mg, 3.81 mg, and 2.80 mg, respectively. Figure 4 This indicates that the iron-modified bacterial residue hydrothermal char prepared in step 1 can effectively slow down the loss of organic carbon and phosphorus in mildly saline-alkali soil.

[0066] Depend on Figure 6 It can be concluded that the soil electrical conductivity decreased by 12 μS / cm when 2% iron-modified biochar was added, while the soil electrical conductivity increased by 35 μS / cm and 74 μS / cm when 4% and 6% iron-modified biochar were added, respectively. This indicates that iron-modified biochar can effectively reduce the pH value of mildly saline-alkali soil and slow down its nutrient loss. However, as the amount used increases, it will increase the salt content in the soil, which is not conducive to the removal of soil salt during the washing process. Therefore, the addition of 2% iron-modified biochar can achieve better results.

[0067] Example 2

[0068] Iron-modified inoculant residue hydrothermal charcoal is used to further improve soil by co-fermentation with inoculant residue. The steps are as follows:

[0069] Soil improved with 2% iron-modified biomass hydrothermal char was mixed with biomass that had passed through a 2mm sieve for fermentation. The biomass addition ratios were 0%, 15%, 20%, 25%, and 30%. During fermentation, the moisture content was maintained at 50-60%, the temperature was 20℃, and the fermentation time was 30 days, resulting in biomass co-fermented improved soil.

[0070] The soil bulk density, pH value, and organic matter content of the soils improved by co-fermentation of inoculum residues were measured in each group, and the results are as follows:

[0071] After co-fermentation with 15%, 20%, 25%, and 30% of inoculum, the soil bulk density decreased from 0.91 g / cm³ to 0.91 g / cm³. 3 Reduced to 0.66 g / cm³ 3 0.55g / cm 3 0.49g / cm 3 0.46 g / cm 3 .

[0072] After adding 15%, 20%, 25%, and 30% of the inoculum and co-fermenting, the pH value of the soil decreased from the original 7.50 to 7.32, 7.24, 7.11, and 6.96, respectively, indicating that co-fermentation can further reduce the pH value of saline-alkali soil.

[0073] After co-fermentation with 15%, 20%, 25%, and 30% of inoculum residue, the soil organic matter content increased from 2.6% to 5.23%, 6.62%, 8.46%, and 10.22%, respectively.

[0074] The proportion of water-stable aggregates in the soil obtained from the co-fermentation of inoculum residue in each group was determined, and the results are as follows: Figure 7 As shown.

[0075] Depend on Figure 7 It can be seen that adding different proportions of inoculum residue can significantly increase the number of water-stable aggregates with a particle size >0.25mm in the soil, and the number of water-stable aggregates with a particle size >0.25mm increases the most when the inoculum residue addition ratio is 30%.

[0076] Example 3

[0077] The preparation of bacterial bran-based solid acid and its further improvement of soil modified by bacterial bran co-fermentation are detailed in the following steps:

[0078] 1. After pulverizing the mushroom residue and passing it through a 100-mesh sieve, mix it evenly with 98% concentrated sulfuric acid at mass-volume ratios of 1:0.5, 1:1, and 1:2 (g / mL). Air dry the mixture at room temperature to obtain three types of mushroom residue-based solid acids. The morphological images of the prepared mushroom residue-based solid acids are shown in the figure. Figure 8 As shown, from Figure 8As can be seen, the obtained bacterial bran-based solid acid is dark black.

[0079] 2. The bacterial bran-based solid acid prepared in step 1 was added to the bacterial bran-fermented soil with a pH of 7.11 obtained by co-fermentation of 25% bacterial bran in Example 2 at a mass ratio of 1%, 5%, and 10%, respectively. After thorough mixing and stabilization with water for 3 days, the improved saline-alkali soil was obtained. The pH values ​​of the soil improved by adding 1%, 5%, and 10% bacterial bran-based solid acid were reduced to 6.56, 5.83, and 5.20, respectively.

[0080] 3. Fill rigid plastic seedling trays (58cm×28cm×3cm) with soil that has been lowered to a pH of 5.20. The soil layer should be 2.5cm thick, and the covering soil layer should be about 0.5cm thick. One week before sowing, dry the seeds in a well-ventilated, shady place. Then, screen the seeds using a salt solution (sodium chloride to water ratio approximately 1:5). Rinse the seeds three times with clean water, removing empty and semi-empty seeds. Disinfect the seeds by soaking them in a 1500-fold dilution of 50% strong chlorine wettable powder for one day. After thoroughly irrigating the rice seedling bed soil, sow (120±1.6)g of sprouted rice per tray. Before emergence, the temperature was controlled at 25-30℃, and after emergence, the temperature was controlled at 20-25℃. The rice seedling period was 30 days. At the same time, a control treatment was carried out, that is, rice seedlings were raised in slightly saline-alkali soil without any treatment (without adding iron-modified hydrothermal carbon, without adding inoculum for co-fermentation, and without adding inoculum-based solid acid). All other operations were the same as those in the above experiment.

[0081] The results showed that the plant height, stem and leaf dry weight, root dry weight, root-to-shoot ratio, and total dry weight of rice increased by 75%, 100%, 50%, 40%, and 88%, respectively, compared with the control. The number of bacteria, fungi, and actinomycetes in the rhizosphere soil of rice seedlings increased by 10%, 30%, and 15%, respectively.

[0082] Example 4

[0083] The impact of improved, slightly saline-alkali soil on rice yield was investigated through the following steps:

[0084] The rice seedlings cultivated in the improved slightly saline-alkaline soil in Example 3 were transplanted into saline-alkaline soils with pH values ​​of 8.5, 8.7, and 8.9, respectively. The row spacing and plant spacing were 20.0 cm × 13.3 cm, with 5-6 seedlings per hill. Chemical fertilizers were applied as base fertilizer before rice planting, with urea, diammonium phosphate, and potassium sulfate applied at 334 kg / hm², respectively. 2 196kg / hm 2 96kg / hm 2 Water management should be carried out using standard methods.

[0085] After harvest, the rice yields reached 358, 320, and 318 kg / mu, respectively. This demonstrates that the method of this invention for improving slightly saline-alkali soil can not only be used for rice seedling cultivation, but also that the cultivated rice seedlings can adapt to the field environment of slightly soda saline-alkali soil and maintain a high rice yield.

[0086] From the above examples, it can be concluded that the iron-modified biochar hydrothermal char of the present invention, whether used alone or in combination with biochar or in combination with biochar and biochar-based solid acid, can improve slightly saline-alkali soil. In particular, the soil improved by iron-modified biochar hydrothermal char in combination with biochar and biochar-based solid acid can be used for rice seedling cultivation and can increase rice yield.

[0087] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method of ameliorating a slightly saline and alkaline soil, characterized by, The method comprises the following steps: adding iron modified fungus straw hydrothermal carbon into slightly salinized soil in a mass ratio of 2%-6%, and then performing bubble field washing to obtain iron modified fungus straw hydrothermal carbon improved soil; The fungus straw is mixed with the iron modified fungus straw hydrothermal carbon improved soil in a mass ratio of 20%-30%, and then fermented and cultured under the condition of a water content of 50%-60% to obtain fungus straw co-fermentation improved soil; the fermentation and culture is performed for 30-40 days at a temperature of 15-25 DEG C; The fungus straw based solid acid is mixed with the fungus straw co-fermentation improved soil in a mass ratio of 5%-10% to obtain slightly salinized improved soil; the fungus straw based solid acid is prepared by mixing fungus straw with concentrated sulfuric acid and carbonizing, and then drying to obtain the fungus straw based solid acid; The iron modified fungus straw hydrothermal carbon comprises fungus straw hydrothermal carbon and iron oxide loaded on the fungus straw hydrothermal carbon; The preparation method of the iron modified fungus straw hydrothermal carbon comprises the following steps: mixing fungus straw with a ferric sulfate solution, and then performing a hydrothermal carbonization reaction to obtain the iron modified fungus straw hydrothermal carbon; the hydrothermal carbonization reaction is performed at a temperature of 180-220 DEG C for 0.5-4 h.

2. The method of claim 1, wherein, The bubble field washing is performed for 3-4 times.

3. The method of claim 1, wherein, The mass fraction of the concentrated sulfuric acid is 98%.

4. The method according to claim 1 or 3, characterized in that, The mass of the fungus straw is 1g, and the volume of the concentrated sulfuric acid is (0.5-5)mL.

5. The improved soil obtained by the method according to any one of claims 1 to 4, characterized in that, The pH value of the improved soil is 5.20-7.

50.

6. Application of the improved soil of claim 5 as rice seedling bed soil.

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