Rapid improvement method for salt-resistant fertile soil in soda saline-alkali dry farmland

Abstract

The invention provides a method for quickly improving salt-resistant fertile soil in soda saline-alkali dry farmland, which comprises the following steps: adjusting a low-salt organic material, mixing and stirring with ferric sulfate powder, carrying out subcritical hydrolysis carbonization, and respectively collecting hydrolysate and solid hydrolyzed carbon; after autumn crops are harvested, conventional straw crushing and stubble cleaning treatment are carried out, hydrolysate and urea are mixed and then sprayed to straw, volcanic slag is spread, and then deep ploughing and field returning are carried out; hydrolyzed carbon and chemical fertilizer are mixed to serve as base fertilizer to be applied in furrows before sowing in spring, and then dry field crops are planted. The number of soil humus and water-stable large aggregates is synchronously and rapidly increased, the salt upward moving amount is reduced, the pH of the soil is reduced, the utilization rate of the fertilizer is increased, the soda saline-alkali soil is improved from the perspective of constructing healthy and fertile plough layer soil, and the grain yield is permanently guaranteed.

Description

Technical Field

[0001] The invention relates to the field of soil improvement and utilization, and relates to a method for quickly improving salt-blocking fertile soil in soda saline-alkali dry fields. Background Art

[0002] China's saline-alkali land is widely distributed and diverse in types. Among them, the soda saline-alkali land located in the Northeast Plain has high salinity and alkalinity, resulting in low soil nutrient effectiveness, low organic matter content, and poor permeability, which affects the growth of crops. Although soda saline-alkali land is mainly medium- and low-yield fields, or even wasteland, as an important arable land reserve resource in China, the investment in scientific research and technology for improving and utilizing soda saline-alkali soil has been increasing in recent years. Traditional methods for improving soda saline-alkali soil mainly include the use of gypsum, aluminum sulfate, organic fertilizer, crop straw, and polymer materials.

[0003] Chemical improvement of soda saline-alkali soil has the purpose of quickly reducing soil salinity and achieving improvement. Among them, exogenous calcium addition (mainly desulfurized gypsum) is a widely used method. Exogenous calcium ions replace exchangeable sodium ions in the soil, improve soil structure, and have a good improvement effect. For example, the patent document (publication number CN103204721A) discloses a method for preparing a rapid composite improver for soda alkaline soil. Soda saline-alkali soil is improved by compounding desulfurized gypsum with peat soil, decomposed farmyard manure and other materials. The patent document (publication number CN107182332A) discloses a method for improving severely soda alkaline soil. Soda saline-alkali soil is improved by compounding desulfurized gypsum with ferrous sulfate and citric acid. However, exogenous calcium addition will lead to an increase in soil ions, resulting in salt damage. Soda saline-alkali soil contains a large amount of calcium carbonate, and this part of the calcium source is fixed in an alkaline environment and cannot be replaced by calcium and sodium. The hydrogen ions in the acidic substance can activate the calcium ions in the soil, realize calcium and sodium replacement, improve the soil structure, and promote soil desalination and dealkali. This improvement method can reduce the addition of exogenous calcium amendments and improve the soil by using the "calcium ions" of the soil itself.

[0004] China is one of the countries with the richest crop straw resources. After returning the straw to the field, the straw composting process takes a long time, and the improvement of soda saline-alkali soil is slow. It needs to be combined with other physical, chemical and biological measures, such as applying soil conditioners while returning the straw to the field. The patent document (publication number CN107182332A) discloses a soda alkalization soil conditioner and its preparation method. Soda saline-alkali soil is improved by applying desulfurized gypsum, calcium chloride and other substances to the decomposed straw. At present, most of them use straw and microbial agents to mix and use microorganisms to decompose straw. The patent document (publication number CN107182332A) discloses a composite microbial agent for degrading crop straw and its preparation method and application. The composite microbial agent is used to degrade crop straw and improve the degradation rate of cellulose, hemicellulose and lignin. The patent document (publication number CN107182332A) discloses a multifunctional bacterium C1 for improving soda saline-alkali soil and its application. The degradation of rice straw is promoted by applying bacterial liquid, rice straw, ammonium sulfate and calcium phosphate into the soil, solving the problem of slow speed and single effect of improving soda saline-alkali soil with rice straw. However, it takes a long time for microorganisms to reproduce, and they are easily affected by external environmental factors. In saline-alkali environments, it is difficult for bacteria to survive and reproduce, resulting in slow decomposition of straw, slow growth of soil organic matter, nutrients and other nutrient elements, limiting the widespread application of returning straw to the field.

[0005] Considering that the decomposition rate of straw is relatively slow when returning straw to the field alone, and it is easily affected by external conditions when combined with microbial agents. As one of the acidic substances, acid-adjusting improvers can quickly reduce soil pH, neutralize soil alkalinity, and react with straw to promote the decomposition of cellulose, lignin and other components in straw. Studies have shown that dilute sulfuric acid can open the encapsulation structure of cellulose, hemicellulose and lignin, reduce the degree of polymerization, increase the contact area between cellulase and cellulose, and increase the reaction rate; sulfuric acid can hydrolyze straw at room temperature and pressure and obtain a high hydrolysis rate. As the concentration of sulfuric acid increases, the hydrolysis rate of rice straw also gradually increases. When the concentration of sulfuric acid is 70%, the hydrolysis rate reaches the maximum value; when the concentration of sulfuric acid is too low (the concentration of sulfuric acid is less than 50%), the effect on promoting straw hydrolysis is not obvious. However, if the concentration of sulfuric acid is too high, the carbonization degree of rice straw will be serious and the hydrolysis rate will be reduced. After carbonization, straw becomes a kind of highly aromatic and stable carbon-rich organic material. Applying it to the field can significantly improve the physical and chemical properties of farmland soil, effectively fix soil nutrients, and provide a good environment for crop growth. Therefore, using straw after carbonization has gradually become an important agronomic measure. Patent document (CN201710497372.3) discloses an inland soda saline-alkali land conditioner and its application. Soda saline-alkali soil is improved by sulfuric acid, natural minerals, organic materials and other materials, but the sulfuric acid concentration of this invention is 10%. It improves saline-alkali soil by adding exogenous ingredients such as straw carbon, cellulose, and humic acid.

[0006] Traditional methods for improving soda saline-alkali land have a single function, poor durability, cannot quickly increase the content of soil organic matter and functional humus, bring more salt into the soil, and are prone to secondary salt return and secondary pollution. There are certain limitations in the promotion and utilization, and the soda saline-alkali soil improved by these methods is mainly used for rice cultivation. Due to the limitation of water sources, a considerable part of saline-alkali land is forced to grow dryland crops. At present, there are few saline-alkali land improvement technologies for growing dryland crops, and they are often improved from the perspective of preventing salt from moving upward or improving fertilizer efficiency. It is impossible to simultaneously achieve rapid humification of straw, increase the number of water-stable large aggregates, reduce the amount of salt moving upward, increase the content of soil humus and increase the fertilizer efficiency of the soil, and it is impossible to establish fertile and healthy tillage layer soil for a long time, thus failing to ensure the continuous grain production. Summary of the invention

[0007] The purpose of the present invention is to provide a method for quickly improving salt-blocking fertile soil in soda saline-alkali dry fields, which improves soda saline-alkali land from the perspective of simultaneously and quickly increasing the amount of soil humus and water-stable macroaggregates, reducing the amount of salt migration, lowering the pH of the soil, and improving the utilization rate of fertilizers, thereby constructing a healthy and fertile topsoil layer, thereby improving grain production and durably ensuring grain production.

[0008] The purpose of the present invention is achieved through the following technical solutions: A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields, comprising the following steps: Step S1: adjusting the low-salt organic material and mixing it with iron sulfate powder to perform subcritical hydrolysis and carbonization, and collecting the hydrolyzed liquid and solid hydrolyzed carbon separately; The water content of the low-salt organic material is adjusted to 55%-65%, the subcritical hydrolysis carbonization temperature is 200°C-220°C, the pressure is 1.6Mpa-2.3Mpa; the mass ratio of ferric sulfate to organic material is 1:10-1:15, and the carbonization time is 0.5-1h; Step S2: After the autumn crops are harvested, conventional straw crushing and stubble removal treatment is performed, the hydrolyzate and urea are mixed and sprayed on the straw, and then volcanic ash is spread, and then deep plowing and returning to the field are performed; Step S3: Before sowing in spring, the hydrolyzed carbon is mixed with chemical fertilizers as base fertilizer for strip application, and then dryland crops are planted.

[0009] As a more preferred technical solution of the present invention, the low-salt organic material in step S1 is agricultural waste such as straw or fungus husks. The fungus husks preferably include wood ear fungus husks, which are wastes from growing fungi such as wood ear fungus using sawdust as the main raw material.

[0010] As a more optimal technical solution of the present invention, the amount of hydrolyzate used in step S2 is 40-50L / mu, the amount of urea used is 0.5-0.8kg / mu, the amount of volcanic slag used is 400-600kg / mu, and the diameter is 0.1-1mm; the soil is deep plowed 20-30cm.

[0011] As a more optimal technical solution of the present invention, the usage amount of the hydrolyzed carbon described in step S3 is 800-1200 kg / mu.

[0012] As a more optimal technical solution of the present invention, the fertilizer described in step S3 is a nitrogen, phosphorus and potassium compound fertilizer, and the fertilizer application amount is 40-50kg / mu.

[0013] Beneficial Effects The present invention is used to improve soda saline-alkali soil with a pH of 8.5-8.9 and a salt content of 0.2%-0.3%. After mixing iron sulfate and low-salt organic materials, subcritical hydrolysis and carbonization are performed, which not only reduces the pH of the hydrolyzate and the hydrolyzed carbon, but also provides iron elements for the soil, promotes the formation of water-stable macroaggregates, reduces the alkaline environment of the soil, is more conducive to the degradation of straw by microorganisms, improves the soil structure, makes the soil less likely to return to salt, and increases water permeability and air permeability, thereby systematically improving the improvement effect. The hydrolyzate prepared by the present invention contains humus-like substances, carbon sources and organic acids that are easily utilized by microorganisms, water-soluble nutrient salts, etc., which can provide initial carbon sources and energy for microbial degradation of straw, thereby promoting rapid degradation and humification of straw in a low temperature environment.

[0014] The hydrolyzed carbon prepared by the present invention can adsorb fertilizers and reduce the pH of rhizosphere soil, thereby improving the effectiveness of soil fertilizers, and can also play a slow-release effect. In addition, the hydrolyzed carbon is rich in iron and can also provide iron elements for plant growth, thereby having the common advantages of organic and inorganic modifiers. Volcanic slag can provide a growth carrier for microorganisms, increase ground temperature, improve soil structure, increase air permeability and water permeability, reduce the capillary effect of soda saline-alkali soil, thereby reducing salt migration, and can also play a role in slow release of trace elements and adsorption of organic carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0016] Figure 1 It is the effect diagram of the hydrolyzate and hydrolyzed carbon in Example 1; Figure 2 The figure is a diagram showing the effects of various treatments in Example 2 on the three-dimensional fluorescence spectrum of water-soluble organic carbon in corn stalk decomposition; Figure 3 This is a diagram showing the effects of various treatments in Example 2 on the humification of corn straw. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the embodiments, but is not intended to limit the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0018] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0019] The invention provides a method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields, comprising the following steps: mixing low-salt organic materials with ferric sulfate, performing subcritical hydrolysis and carbonization, and collecting hydrolyzed liquid and solid hydrolyzed carbon separately; performing conventional straw crushing and stubble-killing treatment after harvesting crops in autumn, mixing hydrolyzed liquid with a small amount of urea and spraying the mixture on the straw, spreading volcanic ash, and then deep plowing and returning the soil to the field; mixing hydrolyzed carbon with chemical fertilizer as base fertilizer before sowing in spring and performing strip application, and then planting and managing dry field crops according to conventional methods.

[0020] Example 1 The mixture of fungus chaff and ferric sulfate was subjected to subcritical hydrolysis carbonization, and the hydrolyzate and hydrolyzed carbon were functionally analyzed. The specific steps are as follows: After removing the outer plastic film of the fungus bran, the bran was broken to disperse the sawdust, and its moisture content was adjusted to 60% and then iron sulfate powder was added (the mass ratio of iron sulfate to bran was 1:10), and it was placed in a subcritical hydrolysis reactor with a volume of 270L, heated to 200℃ and 220℃, and the pressures were 1.6Mpa and 2.3Mpa respectively, and the carbonization time was 1h. After the carbonization, the hydrolyzate and hydrolyzed carbon were collected separately using a solid-liquid separator. The hydrolyzate was stored in a refrigerator at 4℃, and the relevant indicators were measured in time. After the hydrolyzed carbon was naturally air-dried, one part was used for characterization, and the other part was used for adsorption experiments.

[0021] The specific steps of the adsorption experiment are as follows: weigh 20 mg of hydrolyzed carbon and place it in 100 mL of NH4Cl and KNO3 solutions with concentrations of 20 mg / L, 40 mg / L, and 60 mg / L, and oscillate in a constant temperature shaking incubator at 25 °C and 200 r / min for 4 hours, then let it stand for 10 minutes, filter with a 0.45 µm syringe filter, and use a UV-visible spectrophotometer to measure the absorbance of the NH4Cl filtrate at 420 nm, and the absorbance of the KNO3 filtrate at 220 nm and 275 nm, and calculate the corresponding maximum adsorption of nitrate nitrogen and ammonium nitrogen.

[0022] The results show that when the subcritical hydrolysis carbonization temperature is 200℃ and 220℃, the hydrolyzate and hydrolyzed carbon appear dark in appearance, and the particle size of the hydrolyzed carbon becomes smaller ( Figure 1 ), the pH, organic acid concentration, COD and BOD5 content of the hydrolyzate were 1.86 and 1.83, 810.4 mg / L and 880.8 mg / L, 27648 mg / L and 28012 mg / L, 664 and 675 mg / L respectively; the pH of the hydrolyzed carbon was 2.34 and 2.28, and the yield was 53.5% and 52.6%. The maximum adsorption capacity of hydrolyzed carbon for nitrate nitrogen and ammonium nitrogen exceeded 120 mg / g and 50 mg / g respectively. The above results show that the hydrolyzate produced by subcritical hydrolysis and carbonization of the mixture of mushroom bran and ferric sulfate contains both active and inert carbon, and has a low pH, which can provide carbon source and energy for the growth of microorganisms in soda saline-alkali soil, and the hydrolyzed carbon has a high yield, has a good adsorption effect on nutrients, and can slowly release nutrients in the soil.

[0023] Example 2 In order to further confirm the effect of the present invention in promoting straw decomposition, this example is a straw return to the field bag burying experiment conducted in soda saline-alkali land in Da'an City, Jilin Province on October 15, 2021. The pH value of the soil was 8.55 and the soil salt content was 0.21%.

[0024] The specific steps are: cut the dried corn stalks into small pieces of about 1 cm, weigh 100g / piece evenly, set up one group of control and three groups of treatment. The specific design is as follows: The control group was: 200 ml of distilled water was mixed evenly with the straw and put into a nylon bag.

[0025] Treatment 1: The treatment group of straw + urea was as follows: 0.2 g urea was dissolved in 200 ml water, poured into the straw and mixed evenly with the straw, and then put into a nylon bag.

[0026] Treatment 2: The treatment group of straw + urea + hydrolyzate (a small amount) + volcanic ash is as follows: first dissolve 0.2g urea in 170ml distilled water, then add 30ml hydrolyzate, then mix evenly with the straw, then evenly add 5g into the volcanic ash and put it into a nylon bag.

[0027] Treatment 3: The treatment group of straw + urea + hydrolyzate (large amount) + volcanic ash is as follows: first dissolve 0.2g urea in 170ml distilled water, then add 60ml hydrolyzate, then mix evenly with the straw, then evenly add 5g volcanic ash and put it into a nylon bag.

[0028] The nylon bags were buried 25 cm below the soil between two corn plants. Each group was repeated 3 times and corn was planted conventionally.

[0029] On May 10, 2022, straw decomposition samples were collected for indicator determination.

[0030] The results showed that compared with the control, treatment 1, treatment 2 and treatment 3 ( Figure 2 The control, treatment 1, treatment 2 and treatment 3 respectively increased the straw decomposition rate by 15.8%, 43.0% and 48.2%; when urea was added to the straw and urea, volcanic ash and two amounts of carbonized liquid were mixed and added to the straw, the water-soluble organic carbon content in the straw decomposition product increased significantly compared with the control, increasing by 25.45%, 41.27% and 51.57% respectively, and the increase in humic acid-like substances was the most obvious (see Figure 2 ).

[0031] Further analysis found that the total humus content and humic acid content in the straw decomposition under different treatments increased significantly compared with the control. The total humus content of treatment 1, treatment 2, and treatment 3 increased by 6.42%, 21.39%, and 27.27% compared with the control, and the humic acid content increased by 18.75%, 37.90%, and 46.96%, respectively, compared with the control (see Figure 3 The above results show that the simultaneous addition of urea, hydrolyzate and volcanic ash can not only promote the decomposition of straw, but also transform the charcoal decomposed from the straw into more stable humus, which plays an important role in improving the quality of straw return to the field and improving soda saline-alkali soil.

[0032] Example 3 In order to further verify the actual improvement effect of the present invention on soda saline-alkali dry land and its influence on crop growth, a field test was conducted in Da'an City, Jilin Province. The soil pH and salt content of the test plot were 8.55 and 8.92, 0.21% and 0.29%, respectively. The plot area was 5*10=50m 2 .

[0033] The specific process is as follows: the outer packaging of the black fungus chaff, which is mainly wood chips, is removed, crushed, and the moisture content is adjusted to 60%. Iron sulfate powder with a dry weight of 10% of the chaff is added and mixed. The mixture is hydrolyzed and carbonized for 1 hour at a temperature of 220°C and a pressure of 2.3 MPa. The solid-liquid separator is used for solid-liquid separation, and the hydrolyzate and hydrolyzed carbon are collected separately.

[0034] Improved method: On October 10, 2022, after the autumn crops were harvested, conventional straw crushing and stubble treatment was carried out. The hydrolyzate was mixed with a small amount of urea and sprayed on the straw, and then volcanic ash was spread and deep plowing was carried out. The amount of hydrolyzate used in mildly and moderately salinized soils is 40L / mu and 50L / mu, the amount of urea used is 0.5kg / mu and 0.8kg / mu, the amount of volcanic ash used is 400kg / mu, and the depth of returning to the field is about 25cm.

[0035] Before sowing in the spring of 2023, hydrolyzed carbon will be mixed with chemical fertilizer as base fertilizer for strip application. The fertilizer used is disulfide-based compound fertilizer. The amount of fertilizer and hydrolyzed carbon used in mildly and moderately saline-alkali soils is 40kg / mu and 45kg / mu, 800kg / mu and 1200kg / mu respectively. The soybean variety planted is Zhongji 602, and the corn variety is Fumin 985. Planting and daily management are carried out according to local conventional methods.

[0036] Soil and plant samples were collected after harvest in October 2023 for indicator determination.

[0037] At the same time, the following comparative examples were made, and each treatment was repeated 3 times.

[0038] Comparative Example 1: The difference from the improved method is that no hydrolysis liquid and hydrolysis charcoal are added.

[0039] Comparative Example 2: The difference from the improved method is that the hydrolyzate and hydrolyzed carbon prepared by other methods are added. The other methods for preparing the hydrolyzate and hydrolyzed carbon are as follows: after removing the outer plastic film of the fungus chaff, the chaff is crushed through a 100-mesh sieve, the moisture content is adjusted to 60%, iron sulfate is added according to 40% of the dry weight of the chaff, and the mixture is heated to 180°C for carbonization for 4 hours, and the hydrolyzate and hydrolyzed carbon are collected respectively.

[0040] Compared with the control treatment 1, the improved treatment increased the organic matter content in the rhizosphere soil of corn and soybean in the improved soda saline-alkali soil by an average of more than 15%, decreased the pH by an average of 0.4 units, decreased the salt content by an average of 20%, increased the number of water-stable macroaggregates in the rhizosphere soil by an average of 18%, increased the nitrogen, phosphorus and potassium content in the plants by an average of 7%, and increased the yields of soybeans and corn by 16% and 14%, respectively.

[0041] Compared with control treatment 1, control treatment 2 can increase the organic matter content in the rhizosphere soil of corn and soybean in the improved soda saline-alkali soil by more than 8% on average, reduce the pH by 0.3 units on average, reduce the salt content by 10% on average, increase the number of water-stable macroaggregates in the rhizosphere soil by 10% on average, increase the nitrogen, phosphorus and potassium content in the plants by 2% on average, and increase the yields of soybean and corn by 8% and 5%, respectively.

[0042] The above results show that the method of the present invention can significantly increase the organic matter content of the cultivated layer soil, improve the soil structure, prevent the upward migration of salt in the soil, improve the utilization rate of fertilizers, promote the absorption of nutrients by crops, thereby increasing food yields, and the overall effect is significantly better than the hydrolyzate and hydrolyzed charcoal prepared under other conditions.

[0043] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields, comprising the following steps: Step S1: adjusting the low-salt organic material and mixing it with iron sulfate powder to perform subcritical hydrolysis and carbonization, and collecting the hydrolyzed liquid and solid hydrolyzed carbon separately; The water content of the low-salt organic material is adjusted to 55%-65%, the subcritical hydrolysis carbonization temperature is 200°C-220°C, the pressure is 1.6Mpa-2.3Mpa; the mass ratio of ferric sulfate to organic material is 1:10-1:15, and the carbonization time is 0.5-1h; Step S2: After the autumn crops are harvested, conventional straw crushing and stubble removal treatment is performed, the hydrolyzate and urea are mixed and sprayed on the straw, and then volcanic ash is spread, and then deep plowing and returning to the field are performed; Step S3: Before sowing in spring, the hydrolyzed carbon is mixed with chemical fertilizers as base fertilizer for strip application, and then dryland crops are planted.

2. A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields as described in claim 1, comprising the following steps: the low-salt organic material described in step S1 is agricultural waste such as straw or mushroom chaff.

3. The mushroom bran preferably includes wood ear mushroom bran, which is the waste from growing wood ear and other fungi with sawdust as the main raw material.

4. A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields as described in claim 1, comprising the following steps: using 40-50 L / mu of the hydrolyzate described in step S2, using 0.5-0.8 kg / mu of urea, using 400-600 kg / mu of volcanic slag with a diameter of 0.1-1 mm; deep plowing the soil by 20-30 cm.

5. A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields as described in claim 1, comprising the following steps: the amount of hydrolyzed carbon used in step S3 is 800-1200 kg / mu.

6. A method for rapidly improving salt-blocking fertile soil in soda saline-alkali dry fields as described in claim 1, comprising the following steps: the fertilizer described in step S3 is a nitrogen, phosphorus and potassium compound fertilizer, and the fertilizer application amount is 40-50 kg / mu.

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