Rice straw returning method for improving soil fertility

Abstract

The invention relates to the technical field of crop straw treatment and soil improvement, in particular to a rice straw returning method for improving soil fertility, which mainly comprises the following steps: crushing rice straws, soaking with a sodium hydroxide solution, and drying; then selecting specific strains, mixing and fermenting to prepare a microbial agent; preparing a composite additive in proportion; within 1-2 days after the rice is harvested, the pretreated straw, the microbial agent and the composite additive are applied to the field, deep ploughing is conducted, and irrigation is conducted; and finally, performing rotary tillage and soil preparation after straw decomposition, and monitoring and adjusting the pH value of the soil when next-stubble crops are planted. According to the method, straw is pretreated, lignin is destroyed through a sodium hydroxide solution, the particle size is accurately controlled, drying is conducted in cooperation, the microbial decomposition efficiency is improved, straw and soil are fully mixed through accurate ploughing in the field, decomposition is accelerated into nutrients, the straw can be powerfully decomposed through a microbial agent, and the soil micro-ecology is improved; the composite additive supplements various nutrients and enhances the water and fertilizer retention capability of soil.

Description

Technical Field

[0001] The invention relates to the technical field of crop straw processing and soil improvement, and in particular to a method for returning rice straw to fields for improving soil fertility. Background Art

[0002] In agricultural production, soil fertility is a key factor influencing crop yield and quality. With the development of modern agriculture, effectively improving soil fertility and achieving sustainable agricultural development has become a crucial issue. Rice, a globally important food crop, produces a significant amount of rice straw. Traditional methods of rice straw disposal, such as burning, not only waste resources but also cause environmental pollution and damage soil structure. Simply returning rice straw to the fields, however, fails to fully enhance soil fertility due to slow straw decomposition and uneven nutrient release, failing to meet the soil quality requirements of modern agriculture.

[0003] Currently, common straw return methods suffer from deficiencies in their pretreatment phase. Some methods fail to effectively treat the straw, leaving its lignin structure intact and difficult for microorganisms to decompose. This results in the straw remaining in the soil for extended periods, impacting soil aeration and subsequent farming operations. Even some methods employ treatment, but lack precise control over particle size and drying, failing to create optimal conditions for microbial decomposition, significantly reducing the effectiveness of straw return.

[0004] In terms of the application of microbial agents, most existing agents use a single strain or an irrational strain ratio, resulting in limited ability to decompose straw. Furthermore, most agents fail to protect the microorganisms in complex field environments, making them susceptible to inactivation by adverse external factors. This makes it difficult for the microorganisms to survive in the soil for long periods of time and continue to function. Consequently, they are unable to fully decompose straw and effectively improve the soil microecological environment.

[0005] The use of compound additives also presents challenges. Traditional compound additives are simple in formulation and fail to fully replenish the soil's nutrients, resulting in limited improvement in soil water and nutrient retention. The lack of ingredients like polyglutamic acid, which enhance the soil's ability to retain water and nutrients, leads to significant leaching losses of phosphorus, potassium, and trace elements. This prevents crops from continuously and efficiently absorbing nutrients, impacting growth, development, and yield.

[0006] Furthermore, field management also suffers from flaws. Imprecise tillage depth control leads to uneven mixing of straw and soil, resulting in low straw coverage, which hinders straw decomposition and improves soil fertility. Furthermore, a lack of real-time monitoring and precise control of environmental factors such as soil temperature and humidity prevents optimal conditions for microbial activity and straw decomposition, resulting in inefficient straw return.

[0007] In summary, existing rice straw return to fields and related technologies have many shortcomings, failing to effectively improve soil fertility, promote crop growth, and achieve sustainable agricultural development. Therefore, an innovative rice straw return method is urgently needed to address these issues and meet the actual needs of agricultural production. Summary of the Invention

[0008] Technical problems solved

[0009] In response to the above-mentioned shortcomings of the prior art, the present invention provides a method for returning rice straw to the field to improve soil fertility. The present invention pretreats the straw, uses sodium hydroxide solution to destroy lignin, and accurately controls the particle size and conducts drying to improve the efficiency of microbial decomposition. In the field, precise plowing is performed to fully mix the straw with the soil, accelerating the decomposition into nutrients. The microbial agent can strongly decompose the straw and improve the soil microecology. The composite additive supplements a variety of nutrients, enhances the soil's ability to retain water and fertilizer, comprehensively improves soil fertility, and promotes healthy crop growth.

[0010] Technical Solution

[0011] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0012] A method for returning rice straw to fields to improve soil fertility, the method comprising the following steps:

[0013] Step 1: Pre-treating the straw: Harvested rice straw is crushed using a straw crusher to control the particle size of the crushed straw to 2-5 cm. The crushed straw is then placed in a 0.5-1.5% sodium hydroxide solution at a straw to sodium hydroxide solution mass ratio of 1:3-5, and soaked at room temperature for 24-48 hours to allow the straw to fully contact the alkali solution to destroy the lignin structure. After soaking, the straw is transferred to a forced air drying oven and dried at 60-80°C to a moisture content of ≤15% to facilitate subsequent field application and microbial decomposition.

[0014] Step 2, preparation of microbial inoculant: Bacillus subtilis, Bacillus amyloliquefaciens and Brevibacillus laterosporus are selected as functional strains, mixed in a volume ratio of 3:2:1, and inoculated into a liquid culture medium containing 20-30 g / L of glucose, 10-15 g / L of peptone, 2-3 g / L of potassium dihydrogen phosphate, and the balance of deionized water; the inoculated culture medium is placed in a constant temperature shaker, fermented and cultured at a temperature of 30-35° C. and a speed of 180-220 rpm for 48-72 hours, and after the bacterial cell concentration reaches a peak, the cells are collected by centrifugation at a speed of 4000-6000 rpm for 10-15 minutes, and then freeze-dried to prepare a bacterial agent;

[0015] Step 3, preparing a composite additive: weighing humic acid, superphosphate, potassium sulfate and trace elements, and mixing them in a mass ratio of 10:5:3:1, wherein the trace elements are composed of zinc sulfate, boric acid and manganese sulfate in a mass ratio of 3:1:1; putting the mixed materials into a grinder and grinding them into 100-200 meshes to ensure that the components are fully and evenly dispersed to form a composite additive;

[0016] Step 4, field application: Within 1-2 days after rice harvest, evenly spread the pretreated straw on the field surface at a rate of 800-1000 kg per mu; spray the microbial agent prepared in step 2 at a rate of 0.5-1.0% of the mass of the straw, and simultaneously apply the composite additive prepared in step 3 at a rate of 20-30 kg per mu; then use deep plowing machinery equipped with a hydraulic reversing plow to plow the field to a depth of 20-25 cm, ensuring that the straw is completely pressed below the tillage layer and that the straw coverage rate is ≥95%. After plowing, irrigate the field to 60-70% of the soil's saturated water holding capacity and keep the field moist for 15-20 days to create suitable moisture conditions for straw decomposition;

[0017] Step 5. Subsequent management: After the straw decomposition period is over, use a rotary tiller to prepare the land with a tillage depth of 10-15 cm to fully mix the soil with the straw decomposition products; after planting the next crop, monitor the soil pH in real time during the crop growth period using a soil pH sensor. When the pH value is lower than 6.5, add 0.1-0.3% lime water solution through the drip irrigation system to adjust and maintain the soil pH in the appropriate range of 6.5-7.5 to promote the absorption and utilization of nutrients by the crop roots.

[0018] Furthermore, during the soaking process in the sodium hydroxide solution described in step one, 10-15 g of a cellulase preparation is added per cubic meter of straw, and the enzymatic activity of the cellulase is ≥10,000 U / g; after adding the cellulase, the temperature of the soaking system is adjusted to 45-55°C, and the stirring is continued to allow the enzymatic hydrolysis reaction to proceed at this temperature for 6-8 hours. Through the synergistic effect of alkaline treatment and enzymatic hydrolysis, the cell wall structure of the straw is further destroyed, the degradation efficiency of cellulose and hemicellulose is improved, and more available carbon sources are provided for subsequent microbial decomposition.

[0019] Furthermore, during the preparation of the microbial agent described in step 2, a montmorillonite carrier with a mass fraction of 5-10% is added to the bacteria before freeze-drying, and the particle size of the montmorillonite carrier is 5-10 μm; the bacteria and montmorillonite are fully mixed by a high-speed mixer, so that the bacteria are evenly adsorbed in the porous structure of the montmorillonite to form a stable bacterial agent composition. The carrier can not only protect the bacteria from damage from the external environment during storage and application, but also prolong the survival time of the bacteria in the soil, so that its survival time in the field environment is ≥60 days, and it continues to play a role in decomposing straw and improving the soil microecology.

[0020] Furthermore, during the preparation of the composite additive described in step three, 0.5-1.0% by mass of polyglutamic acid, wherein the molecular weight of the polyglutamic acid is 50,000-100,000 Da, needs to be added; the polyglutamic acid is pulverized and mixed with humic acid, superphosphate, potassium sulfate, and trace elements. The high molecular weight hydrophilicity and chelating ability of the polyglutamic acid are utilized to enhance the soil's ability to retain water and nutrients, thereby increasing the soil's water holding capacity by 10-15%, while reducing the leaching loss of phosphorus, potassium, and trace elements, and promoting the continuous absorption of nutrients by crops.

[0021] Furthermore, the deep plowing machinery described in step four adopts a hydraulic reversible plow with a soil crushing device, the plow body depth adjustment accuracy of the hydraulic reversible plow is ≤2cm, and the blade speed of the soil crushing device is 200-300rpm; during the plowing process, the hydraulic system is used to accurately control the plowing depth to 20-25cm, and at the same time, the soil crushing device crushes the soil particles to a particle size of ≤5cm, so that the straw is in full contact with the soil, and the straw coverage rate is ≥95%, avoiding the exposure or accumulation of straw, providing a uniform microenvironment for straw decomposition, and improving the soil permeability and water retention.

[0022] Furthermore, after the irrigation described in step 4 is completed, the field surface is covered with a transparent polyethylene film with a thickness of 0.08-0.12 mm and sealed with soil on all sides; the film covering forms a greenhouse effect, so that the temperature inside the film is maintained at 35-40°C. This temperature range can significantly promote microbial activity, accelerate the straw decomposition process, and shorten the straw decomposition cycle by 5-7 days compared with the uncovered treatment; at the same time, the film covering can also inhibit the germination of weed seeds, reduce the growth of weeds in the field, and reduce the cost of subsequent weeding operations.

[0023] Furthermore, in the subsequent management process described in step five, sunny and windless weather is selected during the tillering period of the crop, and 0.2-0.5% humic acid foliar fertilizer is sprayed with a high-pressure sprayer, wherein the humic acid content in the humic acid foliar fertilizer is ≥50g / L, and the total nutrients of nitrogen, phosphorus and potassium are ≥200g / L; the spraying time is 9-11 am or 3-5 pm, and the spraying amount is 50-60L per mu. Humic acid is supplemented through foliar absorption, which promotes the development of the crop root system, increases the root length by 20-30%, enhances the root system's ability to absorb nutrients in the soil, and thereby improves the crop resistance and yield.

[0024] Furthermore, the trace elements described in step three are composed of zinc sulfate, boric acid, and manganese sulfate, and the mass ratio of the three is 3:1:1, wherein the zinc content of zinc sulfate is ≥35%, the boron content of boric acid is ≥17%, and the manganese content of manganese sulfate is ≥32%; the trace element combination in this ratio can specifically supplement the zinc, boron, manganese and other trace elements required for rice growth, effectively preventing and alleviating problems such as leaf chlorosis caused by zinc deficiency, abnormal flower organ development caused by boron deficiency, and weakened photosynthesis caused by manganese deficiency, making crops grow more robust and increasing yield by 10-15%.

[0025] Furthermore, during the field application process in step four, IoT sensors are arranged in the field to monitor soil temperature and humidity in real time. The temperature measurement accuracy of the sensors is ±0.5°C, and the humidity measurement accuracy is ±2%. When the soil temperature is lower than 30°C or higher than 35°C, or the soil moisture is lower than 60% or higher than 70% of the saturated water holding capacity, the system automatically triggers the irrigation equipment or ventilation device to adjust the irrigation amount and ventilation frequency in real time, control the soil temperature at 30-35°C, and the humidity at 60-70% of the saturated water holding capacity, provide the best environmental conditions for microbial activity and straw decomposition, and realize intelligent and precise management of the straw return process.

[0026] Beneficial effects

[0027] Compared with the known public technology, the technical solution provided by the present invention has the following advantages:

[0028] Beneficial effects:

[0029] 1. The present invention pre-treats the straw, soaks it in sodium hydroxide solution to destroy the lignin structure, and combines it with precisely controlled crushing particle size and drying treatment to greatly improve the efficiency of subsequent microbial decomposition of the straw. When applied in the field, precise tillage depth control and high straw coverage rate allow the straw to be fully mixed with the soil, accelerating the decomposition and conversion of the straw into soil nutrients. The scientific ratio of the composite additives specifically supplements the soil with multiple nutrients, effectively increasing the content of key nutrients such as organic matter, total nitrogen, available phosphorus and fast-acting potassium in the soil, significantly improving soil fertility and creating an excellent soil environment for crop growth.

[0030] 2. The present invention prepares a microbial agent by mixing and fermenting Bacillus subtilis, Bacillus amyloliquefaciens and Brevibacillus laterosporus in precise proportions. The microbial agent has a strong ability to decompose straw. The addition of montmorillonite carrier not only protects the bacteria from environmental damage, but also prolongs their survival time in the soil, and can sustainably play the role of decomposing straw and improving soil microecology. Polyglutamic acid is added to the composite additive to utilize its high molecular hydrophilicity and chelating ability to enhance the soil's ability to retain water and nutrients, reduce nutrient leaching losses, promote the continuous and efficient absorption of nutrients by crops, comprehensively improve the soil's fertilizer and water retention properties, and promote the healthy growth of crops. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Example 1

[0034] Straw pretreatment:

[0035] After the rice is harvested, an appropriate amount of rice straw is selected and crushed using a straw crusher, with the particle size of the crushed straw strictly controlled to be within the range of 2-5 cm; the crushed straw is added to a sodium hydroxide solution with a concentration of 0.5% according to a mass ratio of straw to sodium hydroxide solution of 1:3; during the soaking process, 10 g of cellulase preparation (enzyme activity ≥ 10,000 U / g) is added per cubic meter of straw, the soaking system temperature is adjusted to 45°C, and continuous stirring is carried out to allow the enzymatic hydrolysis reaction to proceed for 6 hours; this operation further destroys the straw cell wall structure through the synergistic effect of alkaline treatment and enzymatic hydrolysis, providing more available carbon source for subsequent microbial decomposition; after the soaking is completed, the straw is transferred to a forced air drying oven and dried at 60°C to a moisture content of ≤15% for subsequent field application and microbial decomposition.

[0036] Preparation of microbial agents:

[0037] Bacillus subtilis, Bacillus amyloliquefaciens and Brevibacillus laterosporus were selected and mixed in a volume ratio of 3:2:1; the mixed strains were inoculated into a liquid culture medium containing 20 g / L glucose, 10 g / L peptone, 2 g / L potassium dihydrogen phosphate and the remainder deionized water; the inoculated culture medium was placed in a constant temperature shaker and fermented and cultured at a temperature of 30°C and a speed of 180 rpm for 48 hours; when the bacterial cell concentration reached a peak, the cells were collected by centrifugation at a speed of 4000 rpm for 10 minutes; before freeze-drying, a 5% by mass fraction of montmorillonite carrier (particle size of 5 μm) was added to the cells, and the cells were fully mixed using a high-speed stirrer so that the cells were evenly adsorbed in the porous structure of the montmorillonite to prepare a microbial agent; the montmorillonite carrier can protect the cells from damage from the external environment during storage and application, prolong the survival time of the cells in the soil, enable the cells to survive for ≥60 days in the field environment, and continuously play a role in decomposing straw and improving soil microecology.

[0038] Compound additive preparation:

[0039] Humic acid, superphosphate, potassium sulfate and trace elements (zinc sulfate, boric acid and manganese sulfate are composed in a mass ratio of 3:1:1, with a zinc sulfate zinc content of ≥35%, a boric acid boron content of ≥17%, and a manganese sulfate manganese content of ≥32%) are weighed and mixed in a mass ratio of 10:5:3:1; during the mixing process, 0.5% by mass of polyglutamic acid (molecular weight of 50,000 Da) is added; all materials are put into a grinder and crushed to 100 mesh so that each component is fully and evenly dispersed to form a composite additive; the addition of polyglutamic acid utilizes its high molecular weight hydrophilicity and chelating ability to enhance the soil's ability to retain water and nutrients, reduce the leaching loss of phosphorus, potassium and trace elements, and promote the continuous absorption of nutrients by crops.

[0040] Field application:

[0041] On the first day after rice harvest, the pretreated straw was evenly spread on the field surface at a rate of 800 kg per mu. The prepared microbial agent was sprayed at 0.5% of the straw mass, and a composite additive was applied at a rate of 20 kg per mu. A hydraulic reversible plow with a soil crushing device (the plow depth adjustment accuracy was ≤ 2 cm, and the soil crushing device blade speed was 200 rpm) was used for plowing. The hydraulic system precisely controlled the plowing depth to 20 cm to ensure that the straw was completely pressed below the tillage layer and the straw coverage rate was ≥ 95%. After plowing, the soil was irrigated to 60% of its saturated water holding capacity, and the field was covered with a transparent polyethylene layer with a thickness of 0.08 mm. The film is covered with a film and sealed with soil on all sides; the film covers form a greenhouse effect, maintaining the temperature inside the film at 35°C, promoting microbial activity, accelerating the straw decomposition process, and inhibiting the germination of weed seeds, reducing the growth of weeds in the field; Internet of Things sensors are arranged in the field (temperature measurement accuracy is ±0.5°C, humidity measurement accuracy is ±2%) to monitor soil temperature and humidity in real time; when the soil temperature is lower than 30°C or higher than 35°C, or the soil humidity is lower than 60% or higher than 70% of the saturated water holding capacity, the system automatically triggers the irrigation equipment or ventilation device to adjust the irrigation amount and ventilation frequency to provide the best environmental conditions for microbial activity and straw decomposition.

[0042] Follow-up management:

[0043] After the straw decomposition period is over, a rotary tiller is used to prepare the land with a tillage depth of 10 cm to fully mix the soil with the straw decomposition products; after planting the next crop, the soil pH is monitored in real time by a soil pH sensor during the crop growth period; when the pH value is lower than 6.5, 0.1% lime water solution is added through a drip irrigation system to adjust the soil pH and maintain it within the appropriate range of 6.5-7.5, thereby promoting the absorption and utilization of nutrients by the crop roots; during the crop tillering period, clear and windless weather is selected, and 0.2% humic acid foliar fertilizer (humic acid content ≥50g / L, total nitrogen, phosphorus and potassium nutrients ≥200g / L) is sprayed with a high-pressure sprayer at a spraying rate of 50L per mu between 9 and 11 am; humic acid is supplemented through foliar absorption, thereby promoting the development of the crop root system and enhancing the root system's ability to absorb nutrients in the soil, thereby improving the crop resistance and yield.

[0044] Example 2

[0045] Straw pretreatment:

[0046] After rice straw is harvested, it is crushed to a particle size of 2-5 cm using a straw crusher; the straw is placed in a 1.0% sodium hydroxide solution at a straw to sodium hydroxide solution mass ratio of 1:4; 12 g of a cellulase preparation (enzyme activity ≥ 10,000 U / g) is added per cubic meter of straw, the soaking system temperature is adjusted to 50°C, and the enzymatic hydrolysis reaction is carried out with continuous stirring for 8 hours; then, the straw is dried in a forced air drying oven at 70°C to a moisture content of ≤15%.

[0047] Preparation of microbial agents:

[0048] Bacillus subtilis, Bacillus amyloliquefaciens, and Brevibacillus laterosporus were mixed in a volume ratio of 3:2:1 and inoculated into a liquid culture medium containing 25 g / L glucose, 12 g / L peptone, 2.5 g / L potassium dihydrogen phosphate, and the balance deionized water; the mixture was fermented and cultured in a constant temperature shaker at 32°C and 200 rpm for 60 hours; the cells were collected by centrifugation at 5000 rpm for 12 minutes, a 7% by mass montmorillonite carrier (particle size 8 μm) was added, and the mixture was mixed in a high-speed blender to prepare a microbial agent.

[0049] Compound additive preparation:

[0050] Humic acid, superphosphate, potassium sulfate and trace elements (zinc sulfate, boric acid and manganese sulfate in a mass ratio of 3:1:1, and the content of each element meets the requirements) are weighed in a mass ratio of 10:5:3:1, polyglutamic acid (molecular weight 75000Da) with a mass fraction of 0.7% is added, and the mixture is crushed to 150 mesh to prepare a composite additive.

[0051] Field application:

[0052] On the first and a half days after rice harvest, pretreated straw is spread on the field surface at 900 kg per mu; microbial agents are sprayed at 0.7% of the straw mass, and 25 kg of compound additives are applied per mu; a hydraulic reversible plow with a soil crushing device (plow depth adjustment accuracy ≤ 2 cm, soil crushing device blade speed 250 rpm) is used for plowing, with a plowing depth of 22 cm to ensure a straw coverage rate of ≥ 95%; after plowing, water is irrigated to 65% of the soil's saturated water holding capacity, and covered with 0.1 mm thick transparent polyethylene film, and the temperature inside the film is maintained at 37°C; the Internet of Things sensor is used to monitor soil temperature and humidity and automatically control environmental conditions.

[0053] Follow-up management:

[0054] After the straw decomposition period, the land is tilled with a rotary tiller to a depth of 12 cm; the next crop is planted and the soil pH is monitored. When the pH is lower than 6.5, it is adjusted to 6.5-7.5 with 0.2% lime solution; during the crop tillering period from 3 to 5 pm, 0.3% humic acid foliar fertilizer is sprayed (all indicators meet the standards), with a spraying amount of 55L per mu.

[0055] Example 3

[0056] Straw pretreatment:

[0057] The harvested rice straw is crushed to a particle size of 2-5 cm; the straw is placed in a 1.5% sodium hydroxide solution at a straw to sodium hydroxide solution mass ratio of 1:5; 15 g of a cellulase preparation (enzyme activity ≥ 10,000 U / g) is added per cubic meter of straw, and enzymolysis is carried out at 55°C for 7 hours with stirring; and the straw is then dried in an 80°C forced air drying oven to a moisture content of ≤15%.

[0058] Preparation of microbial agents:

[0059] Bacillus subtilis, Bacillus amyloliquefaciens, and Brevibacillus laterosporus were mixed in a volume ratio of 3:2:1 and inoculated into a liquid culture medium containing 30 g / L glucose, 15 g / L peptone, 3 g / L potassium dihydrogen phosphate, and the balance deionized water. The mixture was fermented and cultured in a constant temperature shaker at 35°C and 220 rpm for 72 hours. The cells were collected by centrifugation at 6000 rpm for 15 minutes, and a 10% by mass fraction of montmorillonite carrier (particle size 10 μm) was added and stirred at high speed to prepare a microbial agent.

[0060] Compound additive preparation:

[0061] Humic acid, superphosphate, potassium sulfate and trace elements (zinc sulfate, boric acid and manganese sulfate in a mass ratio of 3:1:1, with the content of each element meeting the standard) were weighed in a mass ratio of 10:5:3:1, 1.0% of polyglutamic acid (molecular weight 100,000 Da) was added, and the mixture was crushed to 200 mesh to prepare a composite additive.

[0062] Field application:

[0063] On the second day after rice harvest, 1,000 kg of pretreated straw per mu is spread on the field surface; microbial agents are sprayed at 1.0% of the straw mass, and 30 kg of compound additives are applied per mu; a hydraulic reversible plow with a soil crushing device (plow depth adjustment accuracy ≤ 2 cm, soil crushing device blade speed 300 rpm) is used for plowing, with a plowing depth of 25 cm to ensure a straw coverage rate of ≥ 95%; after plowing, water is irrigated to 70% of the soil's saturated water holding capacity, and covered with 0.12 mm thick transparent polyethylene film to keep the temperature inside the film at 40°C; soil temperature and humidity are monitored and regulated in real time using Internet of Things sensors.

[0064] Follow-up management:

[0065] After the straw decomposition period, use a rotary tiller to prepare the land to a depth of 15 cm; monitor the soil pH after planting the next crop, and adjust it with 0.3% lime water solution when the pH is lower than 6.5; during the crop tillering period, choose suitable weather and spray 0.5% humic acid foliar fertilizer as required, with a spraying amount of 60L per mu.

[0066] Comparative Example 1

[0067] Processing method:

[0068] Except that the enzymatic hydrolysis step in the straw pretreatment is not performed (ie, only soaking with sodium hydroxide solution without adding cellulase and performing enzymatic hydrolysis reaction), other operations are the same as those in Example 2.

[0069] Comparative Example 2

[0070] Processing method:

[0071] Except that no montmorillonite carrier was added during the preparation of the microbial agent, other operations were the same as in Example 2.

[0072] Comparative Example 3

[0073] Processing method:

[0074] Except that polyglutamic acid was not added during the preparation of the composite additive, other operations were the same as in Example 2.

[0075] Comparative Example 4

[0076] Processing method:

[0077] Except that the transparent polyethylene film was not covered during the field application, other operations were the same as in Example 2.

[0078] Comparison of experimental results:

[0079] The above-mentioned embodiment and comparative example were respectively implemented in the test plots of the same area, and the next crop of the same variety was planted. After the crop growth cycle was completed, various indicators were measured. The results are shown in the following table:

[0080]

[0081]

[0082] It can be clearly seen from the data in the table that all indicators of Examples 1-3 are better than those of the comparative example; in the examples, the straw pretreatment by synergistic alkali treatment and enzymatic hydrolysis, the microbial agent with montmorillonite carrier, the composite additive containing polyglutamic acid, the film covering and other operations have significant effects in improving soil fertility, promoting crop growth, shortening the straw decomposition cycle and inhibiting weed growth; for example, the increase in soil organic matter, total nitrogen, available phosphorus and available potassium content in Example 3 is higher than that in other treatments, the soil water holding capacity is increased at the largest rate, the crop root length and yield increase rates are the highest, the straw decomposition cycle is the shortest, and the field weed coverage is the lowest; this fully proves that the rice straw returning method of the present invention has obvious advantages over the traditional method, can effectively improve soil fertility and achieve sustainable agricultural development.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for returning rice straw to fields to improve soil fertility, characterized in that: The method comprises the following steps: Step 1: Pre-treating the straw: Harvested rice straw is crushed using a straw crusher to control the particle size of the crushed straw to 2-5 cm. The crushed straw is then placed in a 0.5-1.5% sodium hydroxide solution at a straw to sodium hydroxide solution mass ratio of 1:3-5, and soaked at room temperature for 24-48 hours to allow the straw to fully contact the alkali solution to destroy the lignin structure. After soaking, the straw is transferred to a forced air drying oven and dried at 60-80°C to a moisture content of ≤15% to facilitate subsequent field application and microbial decomposition. Step 2, preparation of microbial inoculant: Bacillus subtilis, Bacillus amyloliquefaciens and Brevibacillus laterosporus are selected as functional strains, mixed in a volume ratio of 3:2:1, and inoculated into a liquid culture medium containing 20-30 g / L of glucose, 10-15 g / L of peptone, 2-3 g / L of potassium dihydrogen phosphate, and the balance of deionized water; the inoculated culture medium is placed in a constant temperature shaker, fermented and cultured at a temperature of 30-35° C. and a speed of 180-220 rpm for 48-72 hours, and after the bacterial cell concentration reaches a peak, the cells are collected by centrifugation at a speed of 4000-6000 rpm for 10-15 minutes, and then freeze-dried to prepare a bacterial agent; Step 3, preparing a composite additive: weighing humic acid, superphosphate, potassium sulfate and trace elements, and mixing them in a mass ratio of 10:5:3:1, wherein the trace elements are composed of zinc sulfate, boric acid and manganese sulfate in a mass ratio of 3:1:1; putting the mixed materials into a grinder and grinding them into 100-200 meshes to ensure that the components are fully and evenly dispersed to form a composite additive; Step 4, field application: Within 1-2 days after rice harvest, evenly spread the pretreated straw on the field surface at a rate of 800-1000 kg per mu; spray the microbial agent prepared in step 2 at a rate of 0.5-1.0% of the mass of the straw, and simultaneously apply the composite additive prepared in step 3 at a rate of 20-30 kg per mu; then, use a deep plowing machine equipped with a hydraulic reversing plow to plow the field to a depth of 20-25 cm, with a straw coverage rate of ≥95%. After plowing, irrigate the field to 60-70% of the saturated water holding capacity of the soil, and keep the field moist for 15-20 days; Step 5. Subsequent management: After the straw decomposition period is over, use a rotary tiller to prepare the land with a tillage depth of 10-15 cm; after planting the next crop, monitor the soil pH in real time during the crop growth period using a soil pH sensor. When the pH value is lower than 6.5, add 0.1-0.3% lime water solution through the drip irrigation system to adjust the soil pH and maintain it in the appropriate range of 6.5-7.

5.

2. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: During the soaking process in the sodium hydroxide solution in step 1, 10-15 g of cellulase preparation is added per cubic meter of straw, and the enzymatic activity of the cellulase is ≥10,000 U / g; after adding the cellulase, the soaking system temperature is adjusted to 45-55° C. and continuously stirred to allow the enzymatic hydrolysis reaction to proceed at this temperature for 6-8 hours.

3. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: During the preparation of the microbial agent described in step 2, a montmorillonite carrier with a mass fraction of 5-10% is added to the bacteria before freeze-drying, and the particle size of the montmorillonite carrier is 5-10 μm; the bacteria and montmorillonite are fully mixed by a high-speed mixer so that the bacteria are evenly adsorbed in the porous structure of the montmorillonite, so that the survival time in the field environment is ≥60 days.

4. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: During the preparation of the composite additive in step 3, 0.5-1.0% by mass of polyglutamic acid needs to be added, and the molecular weight of the polyglutamic acid is 50,000-100,000 Da.

5. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: The deep plowing machinery described in step 4 uses a hydraulic reversible plow with a soil crushing device. The plow body depth adjustment accuracy of the hydraulic reversible plow is ≤2cm, and the blade speed of the soil crushing device is 200-300rpm. During the plowing process, the hydraulic system is used to accurately control the plowing depth to 20-25cm. At the same time, the soil crushing device crushes the soil particles to a particle size of ≤5cm, so that the straw is fully in contact with the soil, and the straw coverage rate is ≥95%.

6. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: After the irrigation described in step 4 is completed, the field surface is covered with a transparent polyethylene film with a thickness of 0.08-0.12 mm and sealed with soil on all sides; the film covering creates a greenhouse effect and maintains the temperature inside the film at 35-40°C.

7. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: In the subsequent management process described in step 5, sunny and windless weather is selected during the tillering period of the crop, and 0.2-0.5% humic acid foliar fertilizer is sprayed with a high-pressure sprayer, wherein the humic acid content in the humic acid foliar fertilizer is ≥50g / L, and the total nutrients of nitrogen, phosphorus, and potassium are ≥200g / L; the spraying time is 9-11 am or 3-5 pm, and the spraying amount is 50-60L per mu. Humic acid is supplemented through foliar absorption, which promotes the development of the crop root system and increases the root length by 20-30%.

8. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: The trace elements described in step 3 are composed of zinc sulfate, boric acid, and manganese sulfate, and the mass ratio of the three is 3:1:1, wherein the zinc content of zinc sulfate is ≥35%, the boron content of boric acid is ≥17%, and the manganese content of manganese sulfate is ≥32%.

9. The method for returning rice straw to fields to improve soil fertility according to claim 1, characterized in that: During the field application process of step 4, IoT sensors are arranged in the field to monitor soil temperature and humidity in real time. The temperature measurement accuracy of the sensors is ±0.5°C, and the humidity measurement accuracy is ±2%. When the soil temperature is lower than 30°C or higher than 35°C, or the soil humidity is lower than 60% or higher than 70% of the saturated water holding capacity, the system automatically triggers the irrigation equipment or ventilation device to adjust the irrigation amount and ventilation frequency in real time to control the soil temperature at 30-35°C and the humidity at 60-70% of the saturated water holding capacity.

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