Method for improving saline-alkali soil quality of western Jilin paddy field

Abstract

A method for improving saline-alkali soil quality of a paddy field in western Jilin comprises the steps that firstly, according to the conditions that part of the paddy field in Western Jilin is extremely high in saline-alkali content and poor in rice growth, a deep ploughing and straw burying method is adopted, materials are taken nearby, corn straw is smashed into straw sections of 1-5 cm, the straw sections are deeply ploughed into the land by 30-50 cm, the thickness of a straw layer is 10-20 cm, underground salt return is prevented, and the saline-alkali content of the paddy field in the Western Jilin is increased; the operation is carried out after autumn harvest in October; secondly, aiming at the conditions that the sludge layer of the paddy field is thin, most of the soil is sand and the paddy field is shallowly rooted, covering the surface layer by utilizing sludge which is treated in a domestic sewage plant and meets the standard, measuring the heavy metal content of the sludge of the domestic sewage plant before covering, then performing pyrolysis treatment on the sludge, and mixing with activated carbon after pyrolysis treatment, so as to obtain a mixture; surface layer covering is conducted, the application thickness is 5-10 cm, and it is guaranteed that the amount of sludge is smaller than 0.74 kg per square meter; 3, continuously applying the sludge for 5 years and repeatedly applying the corn straws for 5 years according to the saline-alkaline degree of the paddy field soil.

Description

Technical Field

[0001] The invention belongs to the field of soil ecological restoration, and specifically relates to a method for improving the quality of saline-alkali land in rice fields in western Jilin by utilizing nutrients of plant straw, sludge and straw organic carbon. Background Art

[0002] Saline-alkali farmland soil is an important type of terrestrial ecosystem. Due to its wide distribution, according to statistics, its area accounts for about 7% of the total cultivated land in the world, and its area in my country reaches 3.73 million hm2. 2 The saline-alkali land area in western Jilin reached 1.6685 million hm2 2 , making it an important carbon source and carbon pool in terrestrial ecosystems (TC of saline-alkali soil in western Jilin: 24.861±0.786 g·kg -1 ).

[0003] Western Jilin belongs to the Northeast China Transect of Global Climate Change. The region has experienced the evolution of salinization and desertification. It is one of the three major regions in the world where salinization and alkali soil are widely and concentratedly distributed. The area of ​​soda salinization and alkali soil here ranks first in the country. The environmental characteristics of saline-alkali soils largely determine the nutritional status of farmland soils and the physical and chemical properties of the matrix. For example, soil salinization can lead to increased nitrogen fertilizer loss, affect nitrogen denitrification and ammonia volatilization, and affect the activity of microorganisms and their community structure and function; changes in the ionic strength of soil solutions caused by salt can change the activity of organic matter on the surface of soil aggregates; the biogeochemical mechanism of the above-mentioned saline-alkali soil action regulates the soil carbon decomposition and mineralization process. In addition, salinization and alkaliization are serious in western Jilin, and some areas have been converted into rice fields, but the soil has a high alkali content and the soil texture is sandy. Compared with rice fields in Panjin and other places, the soil in some rice fields in Tongyu County in western Jilin is not soft and does not sink deeply when stepped on, resulting in shallow rice roots and extremely low yields. Excluding the costs of seeds and fertilizers, there is almost no income from rice fields.

[0004] At present, the main measures for the treatment of saline-alkali land in western Jilin include engineering measures, chemical measures, physical measures, biological measures, agronomic measures and comprehensive measures. The main engineering measures include land leveling and irrigation and drainage. Land leveling can promote uniform water infiltration and improve the effect of salt leaching and washing, but this method is not suitable for the high salinity of the soil caused by the high groundwater level. Irrigation and drainage is one of the core engineering measures for the treatment of saline-alkali land, including water sources, electricity, pipelines and drainage canal projects, but it has high investment, large engineering volume, and is restricted by terrain and hydrological conditions. It requires top-level design at the national and local levels, and cooperates with soil improvement measures to ensure the implementation of engineering measures. Chemical measures often adjust soil pH by applying chemical modifiers (such as phosphogypsum, desulfurized gypsum, aluminum sulfate, humic acid, etc.), promote calcium-sodium replacement, reduce the concentration of harmful salt ions in the soil, improve soil compaction and air permeability, and help crop growth, but the application of phosphogypsum reduces the content of Fe, Mn and Zn in the soil. Increasing the application of desulfurized gypsum can improve the cohesion of soil particles, improve the aggregate structure, increase porosity, enhance water conductivity, and accelerate salt discharge, but desulfurized gypsum contains alkali metal ions and may return salt when wet. Increasing the application of aluminum sulfate can reduce the soil pH value, but the current price of aluminum sulfate is relatively high. Increasing the application of humic acid can promote the formation of soil aggregate structure and reduce soil alkalinity, but the composition, structure and properties of different humic acids vary significantly, and the improvement effect is different. The main physical measures are the imported soil method and the tillage method. The imported soil method has a large amount of engineering, few soil sources, high investment, and problems in saline-alkali soil treatment, which limits its wide application. Biological measures mainly include salt-alkali tolerant crops, microbial agents, growth regulators and other methods. Biological measures are one of the most effective methods for improving soda saline-alkali land, but the screening of salt-alkali tolerant plants and microbial varieties is limited, and there is a problem of difficulty in adapting to the complex and diverse saline-alkali land environment. It is time-consuming and costly, and cannot fundamentally solve the problem of salt accumulation in the surface layer of saline-alkali land. Agronomic measures mainly include cultivation, fertilization, irrigation, etc. At present, soda saline-alkali paddy fields mostly use agronomic measures for non-saline-alkali land or mild saline-alkali land, lacking special agronomic measures and precise water and fertilizer control technology for medium and severe saline-alkali land. Comprehensive measures are the comprehensive application of the above measures, with better results.

[0005] In Tongyu County in western Jilin, most of the crops are corn and other field crops. A large amount of corn straw resources can be used. Mechanical crushing and burying technology is one of the common methods of returning straw to the field. It is mainly to crush the harvested corn straw into small pieces through a special straw crusher, and bury the crushed straw evenly in the soil through a tillage machine. The purpose is to increase soil organic matter. In this treatment, not only the soil organic matter is increased, but also the groundwater salt return is prevented. After a few years of tillage, the completely decomposed corn straw can increase the soil organic matter. Compared with engineering measures such as drainage and soil addition, it is highly operational, the engineering volume is relatively small, and the effect is obvious.

[0006] The use of sludge to improve the problem of soil desertification in saline-alkali land is mainly considered from the following aspects: the sludge mainly comes from the sludge of sewage treatment plants where no industrial wastewater is collected in urban wastewater. After testing, the heavy metal content in the sludge meets the requirements of the "Pollutant Emission Standard for Urban Sewage Treatment Plants" (GB18918-2002). About 90% of the organic pollutants such as polycyclic aromatic hydrocarbons in the sludge are eliminated during the sewage treatment process, and then fermentation treatment is carried out for 1-2 months to degrade the organic pollutants to meet the standards. Therefore, according to regulations, sludge organic fertilizer can be applied in a limited amount according to the actual situation 1-5 years after the improvement.

[0007] Corn straw and sewage sludge are beneficial to improving the quality of saline-alkali land in rice fields in western Jilin. The advantages are small engineering workload and obvious effect. It prevents salinization caused by rising water levels and salt return, and also improves problems such as shallow crop roots and nutrient deficiencies due to high sand content in the soil, thereby increasing rice yields. Summary of the invention

[0008] The purpose of the present invention is to provide a method for improving the quality of saline-alkali land in rice fields in western Jilin. The method uniformly buries mechanically crushed straw into the soil through tillage to increase soil organic matter and prevent groundwater from returning to salt. After a few years, the fully decomposed corn stalks can increase soil organic matter. Compared with engineering measures such as drainage and irrigation, soil import, etc., the method has strong operability, relatively small engineering volume and obvious effect. The method uses sludge to improve the problem of soil desertification in saline-alkali land, improves the problems of shallow rooting of crops and lack of nutrition due to high sand content in the soil, and increases the yield of rice.

[0009] The present invention is achieved through the following technical solutions: 1. First, ferment and bury the corn stalks: (1) Corn stalk fermentation method: Use an electric stalk crusher to crush the corn stalks before they dry up after the autumn harvest. After crushing, perform simple fermentation for 1-2 months. During fermentation, you can mix cow dung with straw in a ratio of 10:1, or add a fermentation agent. During fermentation, the water management should be such that water just comes out of the hand. During this period, turn the pile 5-6 times. After fermentation, the volume will shrink and the corn stalk will turn brown. (2) Deep burying of straw: Use an orchard trencher with adjustable depth and single-side excavation to dig a 40-50 cm deep trench in the rice field, put the fermented straw 10-20 cm deep, and then dig a trench on one side of the trench so that the soil in the trench can be turned into the previous trench. (3) Finally, use a grader to level the soil.

[0010] 2. Detection and harmless treatment of sludge from domestic sewage treatment plants: (1) Detect the heavy metal content in the sludge, including the eight heavy metals Zn, Cr, Cu, Ni, Pb, As, Hg, and Cd, to see if they comply with the "Agricultural Sludge Pollutant Control Standards" (GB 4284-2018). If they comply, they can be used for agricultural purposes; if they do not comply, they cannot be used, because Article 28 of the "Soil Pollution Prevention and Control Law of the People's Republic of China" clearly prohibits the discharge of sewage and sludge containing excessive amounts of heavy metals or other toxic and hazardous substances, as well as dredging sludge, tailings, slag, etc. that may cause soil pollution, into agricultural land; (2) The amount of sludge applied: Strictly implement the "Agricultural Sludge Pollutant Control Standard" (GB4284-2018), the pollutant limit for the application of sludge from urban sewage treatment plants on agricultural land (Class A sludge ≤ 500 kg / mu per year, continuous use ≤ 5 years), and Class B sludge is prohibited from being used on farmland for growing food; (3) Sludge that has passed the heavy metal and other pollutant tests must be fermented to facilitate the volatilization and degradation of organic pollutants and the removal of harmful microorganisms. The sludge fermentation site is first spread on the ground with plastic sheeting, and then the mixture of sludge and fermentation agent is placed, leaving a number of abandonment holes. The top of the fermentation pile is covered with plastic sheeting, and the fermentation time is 1-2 months, depending on the temperature. Finally, the fermented sludge has no odor or very little odor; (4) The fermented sludge is mixed with corn straw activated carbon, and the application amount of the activated carbon and sludge mixture is 5-10 cm, wherein the amount of sludge is less than 0.74 kg per square meter; (5) After applying the mixture of sludge and activated carbon, the soil is leveled using a grader.

[0011] 3. Repeat application time and subsequent soil management: (1) Sludge and straw activated carbon can be applied continuously for 5 years and cannot be applied again after that; (2) Deep application of corn stalks can be carried out once every five years, and the time interval for deep application of corn stalks can be determined based on the improvement effect of saline-alkali land; (3) Soil management When diverting water for irrigation, the irrigation water can be first filtered through sand to prevent water with too high salt content from entering the field.

[0012] The invention has the advantages of corn straw and sludge improving the quality of saline-alkali land in rice fields in western Jilin. The method buries mechanically crushed straw into the soil evenly through tillage, increases soil organic matter, and prevents groundwater from returning to salt. After a few years, the completely decomposed corn straw can increase soil organic matter. Compared with engineering measures such as drainage and soil addition, the invention has strong operability, relatively small engineering workload, and obvious effect, and prevents salinization caused by returning to salt due to rising water levels. The mixture of sludge and straw organic carbon is applied to the soil surface to improve the problems of shallow crop rooting and nutrient deficiency due to high sand content in the soil, thereby increasing the yield of rice. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The content of heavy metal pollutants in the sludge treated in Example 1; Figure 2 The content of heavy metal pollutants in the sludge treated in Example 2. DETAILED DESCRIPTION

[0014] The present invention will be further described below in conjunction with the embodiments shown in the accompanying tables of the drawings. Example 1

[0015] 1. In Lujiawopu Village, Wulanhua Town, Tongyu County, Jilin Province, corn straw fermentation was carried out: using an electric straw crusher, in early October 2023, after the autumn harvest of corn, the corn straw was crushed, and then a simple fermentation was carried out for 1 month. During the fermentation, the cow dung was mixed with straw at a ratio of 10:1, and 450 g of organic fertilizer fermentation agent was added. The fermented corn straw was about 1000 kg, and it was turned over every 5-7 days during fermentation. When turning the pile, an appropriate amount of water was added, and it was appropriate to just hold the straw and let it come out of water. The pile was turned over 5 times during the period. After fermentation, the volume was reduced and the corn straw was brown; 2. From November 5 to 8, 2023, use a depth-adjustable single-side excavation orchard trencher to dig a 50 cm deep trench in the rice field, put in fermented straw 20 cm deep, and then dig a trench on one side of the trench so that the soil from the trench can be turned into the previous trench. The total area is 20 m 2 ; 3. Finally, use a grader to level the soil; 4. In early March 2023, sludge was collected from the Shangjiahe Sewage Treatment Plant in Shenyang City, and the contents of eight heavy metals, including Zn, Cr, Cu, Ni, Pb, As, Hg, and Cd, were tested. The results were in line with the "Agricultural Sludge Pollutant Control Standards" (GB 4284-2018) and were suitable for agricultural use; 5. According to the application amount, take 15 kg of sludge for fermentation. The sludge fermentation site is first spread on the ground with plastic sheeting, and then 200 g of fermentation agent is placed for fermentation, leaving several abandonment holes. The top of the fermentation pile is covered with plastic sheeting, and the fermentation time is 2 months. Finally, the fermented sludge has no odor or very little odor. Finally, add 150 kg of straw activated carbon and mix evenly for application; 6. On February 20, 2024, 165 kg of the mixture of sludge and straw activated carbon was evenly applied to the saline-alkali land in Lujiawobao Village, Wulanhua Town, Tongyu County, Jilin Province; 7. After applying the mixture of sludge and activated carbon, use a grader to level the soil; 8. On May 20, 2024, rice seedlings will be planted in the improved saline-alkali land; 9. Soil management: When diverting water for irrigation, the irrigation water can be filtered through 1 m thick sand to prevent water with too high salt content from entering the field; 10. On October 28, 2024, production measurement was carried out, 20 m 2 The yield was 17.99 catties, 10% higher than the control. Example 2

[0016] 1. In Sanjiazi Village, Xianghai Township, Tongyu County, Jilin Province, corn straw fermentation was carried out: using an electric straw crusher, in early October 2023, after the autumn harvest of corn, the corn straw was crushed, and then a simple fermentation was carried out for 1 month. During the fermentation, the cow dung was mixed with straw at a ratio of 10:1, and 450 g of organic fertilizer fermentation agent was added. The fermented corn straw was about 1000 kg, and it was turned over every 5-7 days during fermentation. When turning the pile, an appropriate amount of water was added, and it was appropriate to just hold the straw and let it come out of water. The pile was turned over 5 times during the period. After fermentation, the volume was reduced and the corn straw was brown; 2. From November 5 to 8, 2023, use a depth-adjustable single-side excavation orchard trencher to dig a 50 cm deep trench in the rice field, put in fermented straw 20 cm deep, and then dig a trench on one side of the trench so that the soil from the trench can be turned into the previous trench. The total area is 20 m 2 ; 3. Finally, use a grader to level the soil; 4. In early March 2023, sludge was collected from Shenshuiwan Wastewater Treatment Plant in Shenyang City, and the contents of eight heavy metals, including Zn, Cr, Cu, Ni, Pb, As, Hg, and Cd, were tested. The results were in line with the "Agricultural Sludge Pollutant Control Standards" (GB 4284-2018) and were suitable for agricultural use; 5. According to the application amount, take 15 kg of sludge for fermentation. The sludge fermentation site is first spread on the ground with plastic sheeting, and then 200 g of fermentation agent is placed for fermentation, leaving several abandonment holes. The top of the fermentation pile is covered with plastic sheeting, and the fermentation time is 2 months. Finally, the fermented sludge has no odor or very little odor. Finally, add 150 kg of straw activated carbon and mix evenly for application; 6. On February 20, 2024, 165 kg of the mixture of sludge and straw activated carbon was evenly applied to the saline-alkali land in Sanjiazi Village, Xianghai Township, Tongyu County, Jilin Province; 7. After applying the mixture of sludge and activated carbon, use a grader to level the soil; 8. On May 21, 2024, rice seedlings will be planted in the improved saline-alkali land; 9. Soil management: When diverting water for irrigation, the irrigation water can be filtered through 1 m thick sand to prevent water with too high salt content from entering the field; 10. On October 29, 2024, production measurement was carried out, 20 m 2 The yield was 15.65 catties, 12% higher than the control.

Claims

1. A method for improving the quality of saline-alkali land in rice fields in western Jilin, characterized in that: The method comprises the following technical measures: 1) Deep plowing and burying of corn stalks in saline-alkali land of rice fields in western Jilin: Use electric straw crusher to crush corn stalks before they dry up after autumn harvest, and then carry out simple fermentation for 1-2 months. During fermentation, cow dung can be mixed with straw in a ratio of 10:1, or fermentation agent can be added. During fermentation, the water content should be just enough to produce water when held by hand. Turn the pile 5-6 times during the period. After fermentation, the volume will be reduced and the corn stalks will be brown. 2) Deep burying of straw: Use an orchard trencher with adjustable depth and single-side excavation to dig a 40-50 cm deep trench in the rice field, put the fermented straw 10-20 cm deep, and then dig a trench on one side of the trench so that the soil in the trench can be turned into the previous trench; 3) Finally, use a grader to level the soil.

2. The method for improving the quality of saline-alkali land in rice fields in western Jilin according to claim 1, characterized in that: The method comprises detecting and harmlessly treating sludge from a domestic sewage treatment plant: 1) Determine the pollutant content of sludge to see whether it meets the "Agricultural Sludge Pollutant Control Standard" (GB 4284-2018). If it meets the requirements, it can be used for agricultural purposes. If it does not meet the requirements, it cannot be used. This is because Article 28 of the "Soil Pollution Prevention and Control Law of the People's Republic of China" clearly prohibits the discharge of sewage and sludge containing excessive amounts of heavy metals or other toxic and hazardous substances, as well as dredging sludge, tailings, slag, etc. that may cause soil pollution into agricultural land; 2) The amount of sludge applied must strictly follow the "Agricultural Sludge Pollutant Control Standard" (GB4284-2018), the pollutant limit for the application of sludge from urban sewage treatment plants on agricultural land (Class A sludge ≤ 500kg / mu per year, continuous use ≤ 5 years), and Class B sludge is prohibited from being used on farmland for growing food; 3) Sludge that has passed the heavy metal and other pollutant tests must be fermented to facilitate the volatilization and degradation of organic pollutants and the removal of harmful microorganisms. The sludge fermentation site is first spread on the ground with plastic sheets, and then the mixture of sludge and fermentation agent is placed, leaving a number of abandonment holes, and the top of the fermentation pile is covered with plastic sheets. The fermentation time is 1-2 months, depending on the temperature. The fermented sludge has no odor or very little odor; 4) The fermented sludge is mixed with corn straw activated carbon. The application amount of the mixture of activated carbon and sludge is 5-10 cm, and the amount of sludge is less than 0.74 kg per square meter; 5) After applying the mixture of sludge and activated carbon, use a grader to level the soil.

3. The method for improving the quality of saline-alkali land in rice fields in western Jilin according to claim 1, characterized in that: The repeat application schedule and subsequent soil management: 1) Sludge and straw activated carbon can be applied continuously for 5 years and cannot be applied again after that; 2) Deep application of corn stalks can be carried out once every five years, and the time interval for deep application of corn stalks again is determined based on the improvement effect of saline-alkali land; 3) Soil management: When diverting water for irrigation, the irrigation water can be filtered through sand first to prevent water with too high salt content from entering the field.

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