Straw returning method for improving rhizosphere soil quality of baby corn

Abstract

The present application relates to the field of agricultural soil improvement and crop cultivation technology, and more particularly to a method for improving the rhizosphere soil quality of baby bok choy by returning straw to the field, comprising: treating crop straw by pre-aerobic / anaerobic fermentation with Bacillus subtilis, Trichoderma viride and Saccharomycetes, and then compounding the treated straw with a rhizosphere targeted conditioner to form conditioned straw material; and applying the conditioned straw material to different depth layers of the rhizosphere soil in two layers according to the distribution characteristics of the shallow root system of baby bok choy; and supplementing the rhizosphere with an activated promoter at the bud stage and the heading stage of baby bok choy. The present application systematically solves the problem that the existing method for returning straw to the field cannot specifically address the rhizosphere soil quality of baby bok choy.

Description

Technical Field

[0001] This invention relates to the field of agricultural soil improvement and crop cultivation technology, and in particular to a method for returning straw to the field to improve the quality of rhizosphere soil for baby bok choy. Background Technology

[0002] Baby bok choy, an important leafy vegetable, is widely cultivated in northern my country due to its short growth cycle and high economic benefits. However, with the continuous expansion of its planting area and the extension of continuous cropping years, the problem of declining rhizosphere soil quality has become increasingly prominent. This is mainly manifested in reduced soil organic matter content, increased soil acidification or salinization, decreased soil enzyme activity, and an imbalance in the rhizosphere microbial community structure. These problems severely restrict the improvement of baby bok choy yield and quality, and have become a major obstacle to the sustainable development of the baby bok choy industry.

[0003] However, the existing straw return methods have the following technical defects: (1) They are not optimized for the shallow root distribution of baby bok choy. Traditional straw return to the field is buried too deep, and the nutrients released by decomposition cannot be enriched in the main root distribution layer; in addition, the consumption of available nitrogen in the early stage of decomposition competes with the nitrogen of baby bok choy seedlings, inhibiting early growth. (2) The straw has not been biologically pretreated, and the decomposition rate is seriously mismatched with the 60-90-day growing period of baby bok choy. Direct return to the field requires more than 120 days to fully decompose. When baby bok choy is harvested, the straw is still not fully decomposed and cannot play a role in improving the rhizosphere soil during the key growth period; undecomposed straw is also prone to pathogens, increasing the risk of rhizosphere diseases. (3) The systematic regulation of the rhizosphere micro-ecological environment is ignored. The decline in the quality of rhizosphere soil of baby bok choy is manifested by nutrient deficiency, reduced enzyme activity, reduced beneficial microorganisms and proliferation of pathogens. Simply relying on straw return to the field to supplement organic matter cannot rebuild a healthy rhizosphere micro-ecology in the short term and is difficult to solve the problem of continuous cropping obstacles.

[0004] Chinese invention patent CN120836375A, published on October 28, 2025, discloses a combined fertilization method for improving the quality and yield of baby bok choy under drip irrigation conditions. This patent reduces the amount of compound fertilizer by 30% during basal application and combines it with organic fertilizer and compound microbial agents. During the rosette stage, calcium magnesium nitrate fertilizer and urea are applied via drip irrigation, and during the heading stage, potassium sulfate is applied via drip irrigation. However, when this patented technology is directly applied to systematically improve the rhizosphere soil quality of baby bok choy using straw return as the core method, the following shortcomings exist:

[0005] Current technologies do not involve straw return to the field, relying solely on external organic fertilizer supplementation, which fails to achieve in-situ straw return and utilization. The decline in rhizosphere soil quality in baby bok choy is not only manifested in a deficiency of readily available nutrients, but also involves deeper issues such as continuous consumption of organic matter and destruction of aggregate structure. Simply applying organic fertilizer is insufficient to fundamentally increase rhizosphere soil organic matter to ≥16.0 g / kg. Current technologies incorporate all base fertilizers through rotary tillage, failing to provide stratified and targeted nutrient deployment for the shallow root system of baby bok choy. Uniform application cannot create differentiated nutrient and beneficial microbial enrichment zones at different root depths, limiting the efficiency of microecological improvement. Existing compound microbial agents are only used for organic fertilizer mineralization, lacking a systematic design for straw lignocellulose degradation and rhizosphere microecological reconstruction, and lacking a phased and hierarchical functional connection between decomposing bacteria and probiotics. In existing technologies, chemical fertilizers are applied during the rosette and heading stages, without supplementing them with extracts of microbial metabolites containing lipopeptide active substances and extracellular polysaccharides. This makes it impossible to simultaneously activate the rhizosphere microecology during critical growth periods, and the beneficial effects of basal inoculants are difficult to sustain and amplify.

[0006] Therefore, there is an urgent need for a straw return method that can be systematically optimized for the shallow root distribution characteristics and short growth period of baby bok choy, in order to solve the technical problem of poor rhizosphere soil improvement effect caused by the lack of systematic design for the characteristics of baby bok choy in the existing technology. Summary of the Invention

[0007] Therefore, this invention provides a method for returning straw to the field to improve the quality of rhizosphere soil in baby bok choy, in order to solve the problem that existing straw returning methods cannot specifically address the issue of rhizosphere soil quality in baby bok choy.

[0008] To achieve the above objectives, the present invention provides a method for returning straw to the field to improve the quality of rhizosphere soil in baby bok choy, characterized by comprising the following steps:

[0009] Step S1: After drying the crop straw to the preset moisture content and crushing it, mix it with the three strains of compound pretreatment microbial agent according to the preset mass ratio, adjust the moisture content and then pile it for fermentation. When the temperature at the center of the pile reaches the preset temperature, turn the pile over and maintain fermentation until white mycelium appears on the surface of the straw and the color turns yellowish-brown to obtain the pretreated straw material.

[0010] Step S2: The pretreated straw material is mixed with the rhizosphere targeted conditioner at a preset mass ratio to control the soil pH within the range of 6.5-6.8, thereby obtaining the conditioned straw material.

[0011] Step S3: Before planting baby bok choy, cultivate the soil for a predetermined number of days, and apply the prepared straw material in two layers according to the predetermined amount to control the organic acid concentration in the soil 15cm-20cm below the surface to be below 50mg / kg. Rotary tillage is then used to mix the straw with the soil.

[0012] Step S4: Dilute the rhizosphere activator to the preset ratio and apply it to the rhizosphere soil during the rosette and heading stages of the baby bok choy, once each during the rosette and heading stages.

[0013] Further, the crop straw is corn straw or rye straw; the mass ratio of the dried straw to the three-strain compound pretreatment agent is 100:1-100:5; the crop straw is dried to a moisture content of 10%-20% and pulverized to a length of 1cm-5cm; the three-strain compound pretreatment agent contains Bacillus subtilis, Trichoderma viride, and yeast, with a viable count ratio of 2:1:1 and a total viable count ≥1×10⁻⁶. 8 CFU / g.

[0014] Furthermore, the moisture content is adjusted to 50%-65%; during the pile fermentation, the pile is turned when the temperature at the center of the pile reaches 55℃-65℃, and the total fermentation time is 5-10 days. When the temperature at the center of the pile is below 50℃ and the moisture content of the material is below 50%, water is added and the turning frequency is appropriately reduced to reduce heat loss and maintain the pile temperature; the moisture content of the pile is always maintained within the range of 50%-65% by adding water.

[0015] Furthermore, the height of the stack is 1.0m-1.5m and the width is 1.5m-2.0m.

[0016] Furthermore, the mass ratio of the pretreated straw material to the rhizosphere targeted conditioner is 100:3-100:8.

[0017] Furthermore, the soil pH regulator, micronutrient supplement, and rhizosphere probiotic community in the rhizosphere targeted conditioning agent have a mass ratio of 3:3:4. The soil pH regulator is composed of humic acid and gypsum in a mass ratio of 3:1-5:1. The micronutrient supplement is a chelated fertilizer containing 120g / L Ca, 40g / L Mg, 15g / L Zn, and 10g / L B. The rhizosphere probiotic community includes Bacillus amyloliquefaciens and Bacillus mucilaginosus, with a total viable count ≥1×10⁻⁶. 9 CFU / g.

[0018] Furthermore, the baby bok choy is initially cultivated 7-15 days before planting, with a cultivation depth of 20cm-25cm; the total amount of conditioning straw material applied is 300kg / mu-600kg / mu.

[0019] Furthermore, the two-layer application specifically involves: applying a first layer of conditioning straw material, accounting for 60%-70% of the total conditioning straw material, to a depth of 5cm-10cm below the soil surface and mixing it by rotary tillage; and applying a second layer of conditioning straw material, accounting for 30%-40% of the total conditioning straw material, to a depth of 15cm-20cm below the soil surface and mixing it by rotary tillage.

[0020] Furthermore, the rhizosphere activation promoter contains amino acid water-soluble fertilizer, potassium humate, and Bacillus subtilis metabolite extract; when using, it is diluted 200-500 times and applied by hole application or trench application, with an application depth of 5cm-10cm, and the application amount is 10L / mu-20L / mu of diluted liquid each time.

[0021] Furthermore, the total amino acid content of the amino acid water-soluble fertilizer is ≥100g / L; the water-soluble humic acid content of the potassium humate is ≥60g / L; and the Bacillus subtilis metabolite extract is a powder obtained by concentrating and drying the supernatant of Bacillus subtilis fermentation broth, containing lipopeptide active substances and extracellular polysaccharides.

[0022] Compared with existing technologies, this invention systematically solves the technical problem that existing straw return methods cannot specifically improve the soil quality of baby bok choy rhizosphere through synergistic technologies of three strains synergistic pre-fermentation, rhizosphere targeted conditioning, double-layer gradient application, and activation supplementation during key periods.

[0023] Furthermore, this invention uses a compound of Bacillus subtilis, Trichoderma viride, and yeast in a 2:1:1 ratio. The three strains complement each other in carbon source utilization, shortening the pre-fermentation cycle. After the pre-treated straw enters the soil, it enters the rapid decomposition stage in 7-14 days, allowing the straw to release nutrients in a timely manner during the peak nutrient demand period from the seedling stage to the rosette stage of baby bok choy. At the same time, the temperature of the pile is controlled to avoid the temperature exceeding the threshold and causing irreversible inhibition of the microbial community.

[0024] Furthermore, based on the distribution characteristics of lateral roots and fibrous roots of baby bok choy, this invention applies 60%-70% of the conditioning straw into a 5cm-10cm aerobic layer to match the peak fertilizer demand during the rosette stage, and applies 30%-40% into a 15cm-20cm facultative anaerobic layer to match the continuous fertilizer supply during the heading stage. This solves the technical problems of nutrient supply and root absorption being disconnected due to spatial misalignment in traditional returning methods, and the accumulation of deep organic acids inhibiting root respiration. Attached Figure Description

[0025] Figure 1 This is a flowchart of the straw return method for improving the rhizosphere soil quality of baby bok choy according to the present invention.

[0026] Figure 2 This is a bar chart showing the effect of different organic acid concentrations on the TTC reduction strength and relative activity of baby bok choy roots according to the present invention. Detailed Implementation

[0027] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0028] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0030] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] Please see Figure 1 The diagram shown is a process flow chart of a method for improving the quality of rhizosphere soil in baby bok choy according to the present invention.

[0032] This invention provides a method for returning straw to the field to improve the soil quality of the rhizosphere of baby bok choy, comprising the following steps:

[0033] Step S1 is to pre-ferment the crop straw after it has been synergistically pretreated with three strains, so that the straw is partially degraded before entering the soil, so that it can quickly enter the decomposition stage after entering the soil, which matches the short growth period of baby bok choy of 60-90 days.

[0034] Specifically, the crop straw is corn straw or rye straw; the mass ratio of the dried straw to the three-strain compound pretreatment agent is 100:1-100:5; the crop straw is dried to a moisture content of 10%-20% and pulverized to a length of 1cm-5cm; the three-strain compound pretreatment agent contains Bacillus subtilis, Trichoderma viride, and yeast, with a viable count ratio of 2:1:1 and a total viable count ≥1×10⁻⁶. 8CFU / g. The moisture content is adjusted to 50%-65%. During the pile fermentation, the pile is turned when the center temperature reaches 55℃-65℃. The total fermentation time is 5-10 days, during which the pile temperature is maintained within the 55℃-65℃ range by turning the pile. The pile height is 1.0m-1.5m, and the width is 1.5m-2.0m. When the center temperature of the pile is below 50℃, the turning frequency is increased and moisture is added to maintain the pile moisture content at 50%-65%.

[0035] It is understandable that straw needs a 30-45 day adaptation period in the soil before it can enter the rapid decomposition stage. However, baby bok choy enters the seedling stage 15 days after sowing and requires a large amount of nutrients. The nutrient supply is seriously lagging behind the peak nutrient demand of baby bok choy, resulting in hindered growth of baby bok choy seedlings, high yellow leaf rate, and straw residue at harvest time, which greatly weakens the effect of improving soil organic matter.

[0036] Understandably, if a single strain is used for pretreatment, the cellulose-degrading enzyme system is limited and the xylanase secretion is insufficient. The hemicellulose degradation efficiency of straw is far lower than that of the three strains synergistic treatment, and the pre-fermentation endpoint needs to be extended to 12-15 days to be reached. The absence of yeast leads to insufficient accumulation of organic acids in the anaerobic zone inside the pile, resulting in poor straw softening effect and slow decomposition rate after entering the soil.

[0037] Understandably, if the ratio of viable Bacillus subtilis: Trichoderma viride: yeast deviates from 2:1:1, the competitive relationship among the microbial communities becomes unbalanced. When the proportion of fungi is too high, aerobic respiration consumes carbon sources too quickly, and the pile temperature tends to rise rapidly. When the temperature at the center of the pile exceeds 70°C, the metabolic activity of most aerobic microorganisms will be significantly inhibited or even kill, resulting in the opposite of the intended pretreatment effect. When the proportion of bacteria is too high, there is a relative lack of fungi in the system, leading to a decrease in the initial decomposition efficiency of cellulose macromolecules and a reduction in the overall degradation rate. The 2:1:1 ratio has been experimentally verified as the optimal ratio. At this ratio, the three types of microorganisms complement each other in terms of carbon source utilization. Bacillus subtilis utilizes glucose, a cellulose degradation product; Trichoderma viride utilizes cellobiose; and yeast utilizes cellulose dextrin and lactic acid, produced by cellulose hydrolysis, to maximize synergistic degradation efficiency.

[0038] Understandably, if the pile temperature is below 55℃, cellulase activity decreases significantly, requiring a longer pre-fermentation time, and the straw cellulose degradation rate is insufficient, meaning it cannot fully decompose during the baby bok choy's growth period after entering the soil. If the pile temperature exceeds 70℃, microbial activity is suppressed or even kills the microorganisms, resulting in the opposite of the intended pretreatment effect. Microbial activity during composting changes gradually with temperature, not abruptly at a critical temperature. The 65℃-70℃ range is a tolerable transition zone, where microbial activity is somewhat inhibited but basic metabolism can still be maintained, and the temperature can be lowered back to the high-efficiency range by turning the pile to dissipate heat. Above 70℃ is a dangerous threshold, where microbial activity drops sharply or even kills the microorganisms. This invention controls the pile temperature within the 55℃-65℃ range, balancing the high efficiency of cellulase activity and the normal metabolism of the microorganisms, while also providing a safe buffer zone for temperature fluctuations to prevent short-term overheating to the 65℃-70℃ range from triggering the microbial activity inhibition threshold.

[0039] In this embodiment, step S1 includes the following specific steps:

[0040] Step S11: Sun-dry the crop straw until the moisture content is 10%-20%, then crush it into segments 1cm-5cm in length using a straw crusher; mix the crushed straw with a three-strain compound pretreatment agent at a mass ratio of 100:1-100:5, containing Bacillus subtilis, Trichoderma viride, and yeast, with a viable count ratio of 2:1:1 and a total viable count ≥1×10⁻⁶. 8 Add CFU / g of purified water slowly to adjust the moisture content of the mixture to 50%-65%, and pile it into a heap with a height of 1.0m-1.5m, a width of 1.5m-2.0m, and a length depending on the amount of straw.

[0041] Step S12: During the pre-fermentation process, when the temperature at the center of the pile reaches 55℃-65℃, the pile is turned over for the first time. Thereafter, the pile is turned over every 2-3 days to keep the temperature within the range of 55℃-65℃. If the temperature at the center of the pile is below 50℃, the turning frequency is reduced and water is added to keep the moisture content of the pile at 50%-65%. Continue for 5-10 days until white mycelium appears on the surface of the straw, the straw color turns yellowish-brown, the texture softens, and the pile has no odor but has a slightly fermented sour smell. At this point, the pre-fermentation is stopped, and the pretreated straw material is obtained.

[0042] Table 1 shows the data on the effect of straw pre-fermentation parameters on fermentation efficiency, verifying the effect of straw length and moisture content on pre-fermentation efficiency in step S1.

[0043] Table 1. Effects of straw pre-fermentation parameters on fermentation efficiency

[0044] Example 1-1 2-4 60 8 62 58.5 52.3 Examples 1-2 2-4 50 10 58 52.3 45.8 Examples 1-3 1-3 65 7 65 62.1 56.8 Comparative Example 1-1 5-8 60 14 55 42.8 35.2 Comparative Examples 1-2 2-4 40 12 52 48.5 41.2

[0045] Note in Table 1: The straw weight loss rate was calculated by the difference in straw dry weight before and after pre-fermentation. Straw weight loss rate = (straw dry weight before fermentation - straw dry weight after fermentation) / straw dry weight before fermentation × 100%; the cellulose degradation rate was calculated by measuring the change in cellulose content using the anthrone-sulfuric acid method.

[0046] As shown in Table 1, Example 1-1, with straw length of 2cm-4cm, moisture content of 60%, and requiring 8 days to reach the pre-fermentation endpoint, exhibited the best overall performance with a straw weight loss rate of 58.5% and a cellulose degradation rate of 52.3%. Comparative Example 1-1, with straw length of 5cm-8cm, was too long, requiring 14 days to reach the endpoint with a weight loss rate of only 42.8% and a cellulose degradation rate of 35.2%, indicating that excessively long segments are not conducive to inoculant penetration and heat transfer. Comparative Example 1-2, with a moisture content of 40%, was too low, requiring 12 days to reach the endpoint with a weight loss rate of 48.5%, indicating that excessively low moisture content inhibits microbial metabolic activity.

[0047] Table 2 shows the data on the effects of different ratios of viable bacteria of the three strains on the pre-fermentation efficiency of straw and the soil improvement effect, verifying the comprehensive effect of the ratio of viable bacteria of Bacillus subtilis, Trichoderma viride and yeast in step S1 on the pre-fermentation efficiency of straw and the quality of rhizosphere soil of baby bok choy.

[0048] Table 2. Effects of different ratios of viable bacterial strains on soil amendment effects.

[0049] Example 2-1 2:1:1 <![CDATA[1.5×10 8 ]]> 8 18.6 852 Example 2-2 2:1:1 <![CDATA[1.0×10 8 ]]> 10 17.8 815 Example 2-3 2:1:1 <![CDATA[2.0×10 8 ]]> 7 18.9 868 Comparative Example 2-1 1:0:0 <![CDATA[1.0×10 8 ]]> 14 15.2 712 Comparative Example 2-2 3:2:0 <![CDATA[1.0×10 8 ]]> 12 16.1 748

[0050] Table 2 Note: Soil indicators are measured values ​​at the harvest time of baby bok choy (the comparative examples all used triticale straw, an equal amount of pretreated straw material, an equal amount of conditioner, an equal amount of stratified application, and an equal amount of activation promoter supplementation); the yield per baby bok choy plant is the average value of 30 plants; soil organic matter is measured according to NY / T 1121.6-2006 "Soil Testing Part 6: Determination of Soil Organic Matter".

[0051] As shown in Table 2, in Example 2-1, the ratio of calomel:Trichoderma:yeast was 2:1:1, and the total viable bacteria count was 1.5 × 10⁻⁶. 8 The soil organic matter concentration (CFU / g) reached 18.6 g / kg, with a single plant yield of 852 g, demonstrating the best overall effect. In Comparative Example 2-1, the organic matter concentration of a single Bacillus subtilis strain was only 15.2 g / kg, and the yield per plant was only 712 g, significantly lower than the three-strain synergistic group, indicating that a single strain cannot achieve the synergistic degradation of straw lignocellulose. Comparative Example 2-2, without yeast, had an organic matter concentration of 16.1 g / kg, proving that yeast plays an irreplaceable role in promoting straw softening through lactic acid metabolism in the local anaerobic zone of the straw pile. In Examples 2-3, the total viable cell count increased to 2.0 × 10⁻⁶. 8 At CFU / g, the pre-fermentation time was shortened to 7 days, but the soil indicators did not show significant improvement compared to Example 2-1, indicating that an appropriate amount of bacteria can achieve the expected results.

[0052] The function of step S2 is to mix the pretreated straw material with the rhizosphere targeted conditioner to form a conditioned straw material with three functions: pH adjustment, micronutrient supplementation and rhizosphere probiotic regulation, thus upgrading the simple pretreated straw into a multifunctional soil conditioner.

[0053] Specifically, the mass ratio of the pretreated straw material to the rhizosphere targeted conditioner is 100:3-100:8. The rhizosphere targeted conditioner contains a soil pH regulator, a micronutrient supplement, and rhizosphere probiotics in a mass ratio of 3:3:4. The soil pH regulator is composed of humic acid and gypsum in a mass ratio of 3:1-5:1. The micronutrient supplement is a chelated fertilizer containing 120g / L Ca, 40g / L Mg, 15g / L Zn, and 10g / L B. The rhizosphere probiotics include Bacillus amyloliquefaciens and Bacillus mucilaginosus, with a total viable count ≥1×10⁻⁶. 9 CFU / g.

[0054] Understandably, the combination of humic acid and gypsum can adjust the soil pH to a suitable range, eliminating the inhibition on the root growth of baby bok choy. Simultaneously, humic acid contains numerous active functional groups such as carboxyl and phenolic hydroxyl groups, which can release nutrients such as phosphorus, potassium, iron, and zinc fixed in the soil into plant-available forms through complexation / chelation. The calcium released from gypsum... 2+ It can be used to supplement calcium to strengthen cell wall structure and significantly reduce the incidence of dry heartburn caused by calcium deficiency; it can also replace potassium adsorbed on soil colloids. + NH4 + Plasma promotes its release into the soil solution, effectively increasing the content of available potassium.

[0055] Understandably, the synergistic supply of micronutrient supplements ensures the nutritional needs of baby bok choy from the seedling stage to the heading stage. The micronutrients in chelated fertilizers have high water solubility and can be directly absorbed by the baby bok choy roots, with a utilization rate far exceeding that of inorganic salts. Simultaneously, chelating agents protect metal ions from precipitation, prolonging their retention time in the soil solution and ensuring a continuous supply of nutrients.

[0056] Understandably, *Bacillus amyloliquefaciens* secretes lipopeptides and plant hormones, directly promoting root elongation and lateral root development; while *Bacillus mucilaginosus* secretes extracellular polysaccharides, enhancing root-soil adhesion and expanding the root nutrient absorption area. Both work synergistically to colonize the root surface, forming a biofilm that effectively blocks pathogen infection and reduces the risk of rhizosphere diseases. Simultaneously, the extracellular polysaccharides produced by the microbial community's metabolism promote soil particle aggregation, improving soil structure; their decomposition of organic matter accelerates the cycling of elements such as carbon, nitrogen, and phosphorus in the soil, and enhances soil enzyme activity.

[0057] In this embodiment, step S2 includes the following specific steps:

[0058] Weigh out 3%-8% of the pretreated straw material as a rhizosphere-targeted conditioner. This conditioner includes a soil pH adjuster composed of humic acid and gypsum in a 4:1 mass ratio, a micronutrient supplement, and a rhizosphere probiotic flora consisting of Bacillus amyloliquefaciens and Bacillus mucilaginosus in a 1:1 ratio, with a total viable count of 1.2 × 10⁻⁶. 9 Add CFU / g to the pretreated straw material and mix thoroughly using a loader or manually to ensure that the conditioner is evenly dispersed on the surface of the straw.

[0059] Table 3 shows the effects of different amounts of rhizosphere targeted conditioner on soil pH, nutrients, and the incidence of dry heartburn in baby bok choy, verifying the regulatory effect of conditioner addition in step S2 on rhizosphere soil chemical properties and physiological diseases of baby bok choy.

[0060] Table 3. Effects of different amounts of rhizosphere-targeted conditioner on soil pH, nutrients, and incidence of dry-heart fire.

[0061] Example 3-1 3 6.8 17.2 33.5 202.5 4.2 Example 3-2 5 6.6 18.6 36.2 215.7 3.6 Example 3-3 8 6.5 18.8 37.1 220.3 2.8 Comparative Example 3-1 1 7.2 15.8 28.2 182.8 14.9 Comparative Example 3-2 10 6.3 19.1 37.5 223.5 2.5

[0062] Table 3 Note: Soil pH was determined using NY / T 1377-2007; available phosphorus was determined using NY / T 1849-2010 sodium bicarbonate extraction-molybdenum antimony colorimetric method; available potassium was determined using NY / T 889-2004 ammonium acetate extraction-flame photometry method; and the incidence of dry tip burn was the incidence rate of 30 plants surveyed.

[0063] Table 3 shows that the soil pH in Example 3-2 was 6.6, close to the optimal neutral environment for baby bok choy growth. Soil organic matter was 18.6 g / kg, available phosphorus was 36.2 mg / kg, and available potassium was 215.7 mg / kg, with a dry-heart disease incidence of only 3.6%. In contrast, the soil pH in Comparative Example 3-1 was higher at 7.2, with only 28.2 mg / kg of available phosphorus, resulting in a dry-heart disease incidence of 14.9%. This indicates that insufficient conditioner application has limited pH adjustment effects, leading to insufficient nutrient supply, reduced calcium activity, and significantly aggravated dry-heart disease in baby bok choy. Although Comparative Example 3-2 had organic matter of 19.1 g / kg and available potassium of 223.5 mg / kg, reducing the dry-heart disease incidence to 2.5%, the soil pH dropped to 6.3. Furthermore, the conditioner dosage was doubled compared to Example 3-2, yet the improvement in each indicator was limited, making the overall cost-effectiveness lower than a 5% addition.

[0064] The function of step S3 is to adjust the straw material and apply it to the rhizosphere soil in two layers at different depths according to the shallow root distribution characteristics of baby bok choy, so that the nutrients released by the decomposition of straw can form a gradient distribution in the main distribution area of ​​baby bok choy roots, thus achieving precise spatial fertilization.

[0065] Specifically, the initial tillage should be carried out 7-15 days before planting the baby bok choy, with a tillage depth of 20-25cm; the total application rate of the conditioning straw material is 300-600kg / mu. The two-layer application is as follows: the first layer of conditioning straw material, accounting for 60%-70% of the total amount of conditioning straw material, is applied to a depth of 5-10cm below the soil surface and mixed by rotary tillage; the second layer of conditioning straw material, accounting for 30%-40% of the total amount of conditioning straw material, is applied to a depth of 15-20cm below the soil surface and mixed by rotary tillage.

[0066] It is understandable that the lateral roots and fibrous roots of baby bok choy are mainly distributed in the 5cm-15cm soil layer, accounting for 55%-65% of the total root mass. When all the straw is applied to a depth of 15cm, the nutrient supply to the most densely rooted area of ​​baby bok choy in the 5cm-10cm shallow layer is severely insufficient, hindering the development of lateral roots and causing a 15%-25% yellowing rate in the leaves. On the other hand, the straw at a depth of 15cm-20cm produces a large amount of organic acids and reducing substances (such as butyric acid and propionic acid) in the early stage of decomposition. Under anaerobic conditions, these accumulate and inhibit the respiration of baby bok choy roots, leading to root blackening and rot in severe cases. When applied in layers, the first layer (5cm-10cm) decomposes rapidly with aerobic decomposition, providing timely nutrients for the seedling stage, while the second layer (15cm-20cm) decomposes slowly with anaerobic or facultative anaerobic decomposition, providing continuous fertilization for the later head-forming stage. The two layers form a synergistic effect of time and space difference. To determine the critical concentration value at which the above-mentioned organic acids cause harm to the roots of baby bok choy, the following preliminary experiment was conducted. Please refer to [link / reference]. Figure 2 The bar chart shows the effect of different organic acid concentrations on the TTC reduction intensity and relative activity of *Brassica oleracea pubescens* roots. The experiment showed that six organic acid (butyric acid + propionic acid) concentration gradients (0 mg / kg, 40 mg / kg, 50 mg / kg, 60 mg / kg, 70 mg / kg, and 80 mg / kg) were used to determine root activity according to the TTC method described in GB / T 29371-2012. The results showed that at organic acid concentrations of 40 mg / kg and 50 mg / kg, the root TTC reduction intensity was 86.7% and 81.3% of the normal level, respectively, both remaining above 80%. When the concentration increased to 60 mg / kg, the reduction intensity decreased to 68.7%, a decrease of 12.6 percentage points compared to the 50 mg / kg treatment, representing the largest decrease across the entire concentration gradient, indicating a toxic response inflection point near 50 mg / kg. Therefore, 50 mg / kg was determined as the safe threshold for *Brassica oleracea pubescens* roots to tolerate soil organic acids.

[0067] In this embodiment, step S3 specifically includes the following steps:

[0068] Step S31: 7-15 days before planting baby bok choy, perform initial plowing of the planting field to a depth of 20cm-25cm. Use a moldboard plow to turn the soil over, bringing the deep soil to the surface. After initial plowing, use a notched disc harrow to break up large clods and level the soil.

[0069] Step S32: Weigh out 400 kg / mu of conditioning straw material and spread it evenly on the field surface using a spreader or manually. First, take 60%-70% of the total amount of conditioning straw material and spread it on the field surface. Then, use a rotary tiller to till it to a depth of 10cm-12cm, tilling 2-3 times to fully mix the first layer of straw with the 5cm-10cm soil layer. Next, take 30%-40% of the total amount of conditioning straw material and spread it on the tilled field surface. Then, use a rotary tiller to till it again to a depth of 18cm-22cm, tilling 2-3 times to fully mix the second layer of straw with the 15cm-20cm soil layer. After rotary tilling, the soil surface should be flat, the straw should be evenly distributed, and there should be no obvious straw accumulation.

[0070] Step S33: After rotary tillage, let the soil stand for 7-10 days, during which time the soil moisture content should be maintained at 60%-75%. If the soil is too dry, irrigation is required. After the straw material has been initially stabilized in the soil, baby bok choy can be sown or transplanted.

[0071] Table 4 shows the effects of different application methods on the yellowing rate, yield, and deep organic acid concentration of baby bok choy, verifying the effect of the stratified application method in step S3 on the root distribution and yield of baby bok choy.

[0072] Table 4. Effects of different application methods on yellowing rate, yield, and concentration of deep organic acids in baby bok choy.

[0073] Example 4-1 Double layer 60 5-10 15-20 3.5 828 44 Example 4-2 Double layer 65 5-10 15-20 2.2 852 39 Example 4-3 Double layer 70 5-10 15-20 2.8 845 35 Comparative Example 4-1 single layer - - 15-20 15.5 745 91 Comparative Example 4-2 single layer 100 5-10 - 1.8 762 6

[0074] Table 4 Note: Leaf yellowing rate was investigated 25 days after sowing; yield per plant was the average of 30 plants at harvest; organic acid concentration in the 15-20cm soil layer was the total amount of butyric acid and propionic acid determined by gas chromatography on the 7th day after rotary tillage and settling (before transplanting).

[0075] Table 4 shows that the organic acid concentration in the 15cm-20cm soil layer of the double-layer application groups (Examples 4-1 to 4-3) was 35mg / kg-44mg / kg, all below the safety threshold of 50mg / kg. Example 4-2 showed the best overall effect with a leaf yellowing rate of only 2.2% and a yield of 852g per plant. In contrast, Comparative Example 4-1, where straw was concentrated in a deeper soil layer, had an organic acid concentration as high as 91mg / kg, far exceeding the threshold. This high concentration of organic acid inhibited root respiration in the baby bok choy under anaerobic conditions, leading to hindered lateral root development and reduced root absorption. Simultaneously, the shallow 5cm-10cm layer lacked organic material input, preventing the readily available nutrients released from straw decomposition from accumulating in the most densely rooted area of ​​the baby bok choy, resulting in a leaf yellowing rate as high as 15.5% and a yield of only 745g per plant. Comparative Example 4-2 involved concentrated application of straw into a shallow soil layer of 5-10 cm, keeping the baby bok choy roots in a shallow, nutrient-rich environment for an extended period. This lack of nutrient drive to penetrate deeper inhibited the vertical expansion of the roots, resulting in insufficient root development and an organic acid content of only 6 mg / kg. Although this ensured a supply of readily available nutrients in the shallow soil during the seedling stage, with a yellowing rate of only 1.8%, the lack of continuous nutrient release from deeper soil layers in the later stages of growth prevented the roots from expanding downwards to absorb nutrients. This resulted in poor head compaction and a yield of only 762 g per plant, lower than the double-layer application groups. These results indicate that using a double-layer gradient application method with the first layer comprising 60%-70% of the total soil layer not only ensured nutrient enrichment in the shallow roots and reduced the yellowing rate, but also guided some roots to penetrate deeper to utilize nutrients, improving head compactness and achieving a synergistic improvement in both yield and quality of baby bok choy.

[0076] The function of step S4 is to apply rhizosphere activation promoters in stages during the two critical periods of nutrient demand in baby bok choy, namely the rosette stage and the heading stage. This continuously activates the activity of rhizosphere soil enzymes and microbial metabolism over time, so that the soil improvement effect established by S1-S3 can be fully realized and sustained throughout the entire growth period of baby bok choy.

[0077] Specifically, the rhizosphere activation promoter comprises amino acid water-soluble fertilizer, potassium humate, and Bacillus subtilis metabolite extract. It is diluted 200-500 times and applied by hole or trench application to a depth of 5-10 cm, with each application using 10-20 L of diluted liquid per acre. The total amino acid content of the amino acid water-soluble fertilizer is ≥100 g / L; the water-soluble humic acid content of the potassium humate is ≥60 g / L; and the Bacillus subtilis metabolite extract is a powder obtained by concentrating and drying the supernatant of the Bacillus subtilis fermentation broth, containing lipopeptide active substances and extracellular polysaccharides.

[0078] It is understandable that the free amino acids contained in amino acid water-soluble fertilizers can be directly absorbed by the root system and participate in protein synthesis, increasing the content of soluble protein; at the same time, as signaling molecules, they induce the root system to secrete organic acids and extracellular enzymes, activating rhizosphere nutrients, promoting head enlargement, and increasing yield per plant. The small molecule active functional groups of water-soluble humic acid in potassium humate stimulate the development of lateral roots and root hairs, expanding the root absorption area. The K+ released from potassium humate... + It participates in the loading and transport of photosynthetic products into the phloem of the head, promoting sugar accumulation and increasing soluble sugar content, head compactness, and yield per plant. Lipopeptide active substances in the extract of microbial metabolites disrupt the cell membrane integrity of pathogenic fungi, leading to their death; simultaneously, it induces systemic resistance in plants, enhances the activity of defense enzymes, and, together with the physical barrier of the biofilm formed by extracellular polysaccharides on the root surface, reduces the incidence of root rot through a dual mechanism, ensuring plant health and preventing a decline in assimilation capacity due to disease. This maintains high levels of soluble protein and soluble sugar accumulation, consolidating the yield-enhancing effect.

[0079] In this embodiment, step S4 specifically includes the following steps:

[0080] Step S41: 25-35 days after sowing the baby bok choy, during the rosette stage, when the baby bok choy has unfolded 8-10 leaves, dilute the root activation promoter 300 times and use 10-20L of diluted solution per acre. Apply it by hole application: hole depth 5cm-10cm, hole spacing 15cm-20cm, apply 50mL-100mL of diluted solution to each hole near the roots of the baby bok choy, and immediately cover with soil and water after application.

[0081] Step S42: 45-60 days after sowing, during the heading stage of baby bok choy, when the head of the baby bok choy has begun to close, apply a second application using the same dosage and method as in S41. The second application focuses on supplementing potassium and nutrients needed for protein synthesis, which is particularly crucial for improving the firmness of the baby bok choy head and the content of soluble protein.

[0082] Step S43: After two applications, avoid flooding within 24 hours to prevent the nutrients of the activation promoter from being leached away by water; drip irrigation can be used for supplemental watering, with each drip irrigation amount of 5L / mu-8L / mu, so that the nutrients of the rhizosphere activation promoter can be fully absorbed by the soil.

[0083] Table 5 shows the effects of different application times and timings on the yield, quality, and root rot incidence of baby bok choy, verifying the regulatory effect of the application times and timings of the rhizosphere activation promoter in step S4 on the quality of baby bok choy.

[0084] Table 5. Effects of different application times and timing on yield, quality, and root rot incidence of baby bok choy.

[0085] Example 5-1 Rosette stage + bulb stage 10 825 12.2 34.2 4.5 Example 5-2 Rosette stage + bulb stage 15 856 12.8 36.4 3.2 Example 5-3 Rosette stage + bulb stage 20 861 13.5 36.9 2.9 Comparative Example 5-1 Only the lotus period 15 790 11.2 31.8 8.5 Comparative Example 5-2 Only during the heading period 15 773 10.4 31.0 9.3

[0086] Table 5 Note: Soluble protein was determined by the Coomassie brilliant blue colorimetric method; soluble sugar was determined by NY / T 1278 "Determination of soluble sugar in vegetables and their products by copper reduction iodide method"; root rot incidence rate was the incidence rate of 30 plants surveyed; yield per plant was the average of 30 plants at harvest time.

[0087] As shown in Table 5, Example 5-2 had a single-plant yield of 856g, soluble protein of 12.8mg / g, soluble sugar of 36.4mg / g, and a root rot incidence rate of only 3.2%, making it the most cost-effective overall. Comparative Example 5-1, which only received supplemental fertilization during the rosette stage, had a single-plant yield of only 790g, soluble sugar of only 31.8mg / g, and a root rot incidence rate that rebounded to 8.5%, indicating that the activator and promoter applied during the rosette stage were essentially depleted by the heading stage. Comparative Example 5-2, which only received supplemental fertilization during the heading stage, had a soluble protein of only 10.4mg / g, a yield of only 773g, and a root rot incidence rate of 9.3%, indicating that the failure to apply supplemental fertilization in time during the rosette stage resulted in limited vegetative growth, insufficient photosynthetic area of ​​the leaves, and the topdressing during the heading stage could not compensate for the earlier growth deficit.

[0088] Examples and Comparative Examples

[0089] Example 1

[0090] The lower limit parameters were used for each treatment step: S1: Triticale straw, moisture content 10%, crushed to 4cm-5cm segments; mixed with three strains of pretreatment inoculant at a mass ratio of 100:1, wherein the ratio of calcined straw:Trichoderma:yeast = 2:1:1, and the total viable count was 1.0 × 10⁻⁶. 8 CFU / g; moisture content 50%; pile height 1.0m, width 1.5m; pile temperature 50℃-55℃, turning interval 3 days; pre-fermentation reaches the endpoint after 10 days. S2: Pre-treated straw material and rhizosphere targeted conditioner are mixed at a mass ratio of 100:3; the conditioner contains humic acid: gypsum = 3:1, trace element supplements, and rhizosphere probiotics. S3: Initial plowing 15 days before planting, plowing depth 20cm; total amount of conditioned straw material 300kg / mu; first layer 60% applied 5cm-10cm, application amount 180kg / mu, rotary tilled 10cm×2 times; second layer 40% applied 15cm-20cm, application amount 120kg / mu, rotary tilled 18cm×2 times. S4: Apply once each during the rosette stage and the heading stage; the rhizosphere activator contains amino acids ≥100g / L, potassium humate ≥60g / L, and Bacillus subtilis metabolite extract, diluted 200 times, 10L / acre each time, applied in holes 5cm deep.

[0091] Results: Soil organic matter content was 17.2 g / kg, yield per plant was 825 g, soluble protein content was 12.2 mg / g, soluble sugar content was 34.2 mg / g, and the overall results were satisfactory.

[0092] Example 2

[0093] Median parameters were used for each treatment step: S1: Triticale straw, moisture content 15%, crushed to 2cm-4cm segments; mixed with three strains of pretreatment inoculant at a mass ratio of 100:3 (blight:Trichoderma:yeast = 2:1:1, total viable count 1.5×10⁻⁶). 8 CFU / g); moisture content 60%; pile height 1.2m, width 1.8m; first turn the pile when the pile temperature reaches 58℃, then turn it every 2 days thereafter, maintaining 50℃-62℃; pre-fermentation reaches its endpoint in 8 days. S2: Pre-treated straw material is mixed with rhizosphere targeted conditioner at a mass ratio of 100:5; the conditioner contains humic acid: gypsum = 4:1, trace element supplements, and rhizosphere probiotics. S3: Initial plowing 10 days before planting, plowing depth 22cm; total conditioned straw material 400kg / mu; first layer 65% applied 5cm-10cm, application amount 260kg / mu, rotary tilled 12cm×2 times; second layer 35% applied 15cm-20cm, application amount 140kg / mu, rotary tilled 20cm×2 times. S4: Apply once each during the rosette stage and the heading stage; dilute the rhizosphere activation promoter 300 times, apply 15L / acre each time, and apply in holes 8cm deep.

[0094] Results: Soil organic matter content was 18.6 g / kg, yield per plant was 856 g, soluble protein content was 12.8 mg / g, and soluble sugar content was 36.4 mg / g, which was the best overall result.

[0095] Example 3

[0096] Each processing step uses the upper limit parameters: S1: Corn stalks, moisture content 20%, crushed into 1cm-3cm segments; mixed with three strains of pre-treatment inoculant at a mass ratio of 100:5 (blight:Trichoderma:yeast = 2:1:1, total viable count 2.0 × 10⁻⁶). 8 CFU / g); moisture content 65%; pile height 1.5m, width 2.0m; first turn the pile when the pile temperature reaches 65℃, then turn it every 2 days thereafter, maintaining 55℃-65℃; pre-fermentation for 7 days to reach the endpoint. S2: Pre-treated straw material and rhizosphere targeted conditioner are mixed at a mass ratio of 100:8; the conditioner contains humic acid: gypsum = 5:1, trace element supplements, and rhizosphere probiotics including Bacillus amyloliquefaciens: Bacillus mucilaginosus = 1:1. S3: Initial plowing 7 days before planting, plowing depth 25cm; total amount of conditioned straw material 600kg / mu; first layer 70% applied 5cm-10cm, application amount 420kg / mu, rotary tilled 12cm×3 times; second layer 30% applied 15cm-20cm, application amount 180kg / mu, rotary tilled 22cm×3 times. S4: Apply once each during the rosette stage and the heading stage; dilute the rhizosphere activation promoter 500 times, apply 20L / acre each time, and apply in furrows to a depth of 10cm.

[0097] Results: Soil organic matter 19.2 g / kg, single plant yield 861 g, soluble protein 13.5 mg / g, soluble sugar 36.9 mg / g.

[0098] Comparative Example 1

[0099] Using the same process parameters and formula as in Example 2, but omitting the S1 biological pretreatment step, the rye straw was dried to a moisture content of 15% and then crushed to 2cm-4cm. It was then directly mixed with the conditioner and applied in layers in S3 without undergoing pre-fermentation treatment.

[0100] Results: Soil organic matter content was 14.2 g / kg, yield per plant was 685 g, soluble protein was 9.2 mg / g, and soluble sugar was 27.8 mg / g. This demonstrates that S1 biological pretreatment is a key step in achieving rapid straw decomposition and matching the growth period of baby bok choy.

[0101] Comparative Example 2

[0102] Using the same process parameters and formula as in Example 2, but omitting the S2 conditioner compounding step, the S1 pretreated straw material was directly applied to the soil in a two-layer application method, with a total application amount of 400 kg / mu, without adding any conditioner.

[0103] Results: Soil organic matter was 15.3 g / kg, available phosphorus was 29.8 mg / kg, available potassium was 185.6 mg / kg, yield per plant was 728 g, and the incidence of dry tip burn was 12.5%. This demonstrates that the S2 rhizosphere-targeted conditioner plays an irreplaceable role in activating phosphorus and potassium elements, regulating soil pH, and inhibiting dry tip burn disease.

[0104] Comparative Example 3

[0105] Using the same process parameters and formula as in Example 2, but omitting the layered application in S3, the straw material with an application rate of 400 kg / mu was applied to a depth of 15 cm below the soil surface in one go, and then rotary tilled and mixed.

[0106] Results: Soil organic matter content was 15.8 g / kg, leaf yellowing rate was 15.5%, yield per plant was 745 g, and soluble sugar content was 30.6 mg / g. This demonstrates that the S3 stratified gradient application is a key design for precisely enriching nutrients in the dense root zone of baby bok choy, avoiding localized nutrient overload, and inhibiting root respiration.

[0107] Comparative Example 4

[0108] The same process parameters and formula as in Example 2 were used, but the S4 step of applying the supplementary agent was omitted, and no rhizosphere activation promoter was applied during the entire growth period of the baby bok choy.

[0109] Results: Soil organic matter content was 15.2 g / kg, yield per plant was 762 g, soluble protein content was 10.8 mg / g, and root rot incidence was 10.2%. This demonstrates that applying S4 rhizosphere activator in multiple applications is a key step in maintaining rhizosphere enzyme activity, ensuring continuous nutrient supply, and maintaining disease control during the later stages of baby bok choy growth.

[0110] Comparative Example 5

[0111] The conventional straw return method was used as a comprehensive control: the moisture content of corn straw was 20%, the length was 3cm-5cm, and it was not pre-fermented. It was fully plowed to a soil layer of 30cm at a rate of 800kg / mu, and rotary tilled twice. No conditioner was added, it was not applied in layers, and no activating and promoting agents were applied during the growth period.

[0112] Results: Soil organic matter was 13.5 g / kg, available nitrogen was 92.3 mg / kg, yield per plant was 658 g, soluble protein was 8.8 mg / g, leaf yellowing rate was 22.1%, and root rot incidence was 18.5%. Conventional straw return methods, due to poor deep aeration and slow straw decomposition, cause continuous stress to the roots of baby bok choy. All indicators were significantly lower than those of this invention, demonstrating the comprehensive superiority of the four-step linkage technology of this invention.

[0113] Overall beneficial effects analysis results

[0114] To comprehensively evaluate the overall performance of the technical solution of the present invention, statistical analysis was performed on the test results of the overall embodiments 1-3 and comparative examples 1-5.

[0115] Table 6. Comparison of overall test results between the complete embodiment and the comparative example.

[0116] Example 1 17.2 825 12.2 34.2 4.2 4.1 qualified Example 2 18.6 856 12.8 36.4 2.2 3.6 qualified Example 3 19.2 861 13.5 36.9 2.5 3.1 qualified Comparative Example 1 14.2 685 9.2 27.8 18.1 16.7 Unqualified Comparative Example 2 15.3 728 10.1 29.5 12.7 12.5 Unqualified Comparative Example 3 15.8 745 10.5 30.6 15.5 15.8 Unqualified Comparative Example 4 15.2 762 10.8 31.2 8.4 6.3 Unqualified Comparative Example 5 13.5 658 8.8 25.5 22.1 13.5 Unqualified

[0117] Note in Table 6: Referring to the requirement of soil organic matter ≥16.0g / kg in NY / T 391-2021 "Green Food Production Area Environmental Quality", and combined with the commercial standards for yield, appearance quality and disease incidence in baby bok choy production practice, the comprehensive judgment qualification standards are as follows: Soil organic matter ≥16.0g / kg, single plant yield ≥780g, soluble protein ≥11.0mg / g, yellowing rate ≤5%, and dry heart disease incidence ≤5% are qualified; soluble sugar is used as a quality reference indicator.

[0118] Explanation of the overall beneficial effects

[0119] I. The principle of precise matching between the synergistic pretreatment of three strains and the short growth period of baby bok choy

[0120] The principle of the three-strain synergistic pretreatment in this invention lies in utilizing the complementary carbon source utilization and synergistic effect of metabolites of three types of microorganisms—Bacillus subtilis, Trichoderma viride, and yeast—to achieve partial degradation of straw during the pre-fermentation stage, laying the foundation for rapid decomposition after entering the soil. Bacillus subtilis, an aerobic or facultative aerobic bacillus, secretes large amounts of cellulase (CMCase, FPase, and xylanase) during the aerobic stage of the early pre-fermentation period, decomposing straw cellulose into glucose and cellobiose. Trichoderma viride, an aerobic cellulose-decomposing fungus, enhances the mechanical breaking and enzymatic penetration efficiency of straw structure by secreting cellulase systems and xylanase, and utilizing its widely distributed hyphal network to physically entangle straw fiber bundles. Yeast exerts facultative anaerobic metabolic functions in the slightly hypoxic zone inside the straw pile, further fermenting the cellulose hydrolysis products to produce lactic acid and ethanol, lowering the local pH to 4.5-5.5, and promoting the weakly alkaline softening of lignin in the straw. Three types of microorganisms form a synergistic degradation system of "aerobic cellulose decomposition + facultative anaerobic organic acid softening," which improves the cellulose degradation rate compared to a single strain. After pre-fermentation treatment, straw can enter the rapid decomposition stage within 7-14 days after entering the soil. This allows the nutrients released from the straw decomposition to be supplied to the roots for absorption during the peak nutrient demand period from the seedling stage to the rosette stage of baby bok choy, thus solving the fundamental contradiction of "decomposition lagging behind demand" in traditional straw return to the field.

[0121] II. The Spatial Coupling Principle of Layered Gradient Application and the Shallow Root System of Baby Cabbage

[0122] The principle behind this invention's tiered gradient application lies in the response mechanism of the baby bok choy root system morphology to nutrient gradients and the optimized spatial fertilization design. Baby bok choy roots are primarily taproots, with the densest root distribution occurring in the 5cm-15cm layer. The design of the first layer (5cm-10cm) accounting for 60%-70% of the total application is based on the following mechanism: this layer is where the lateral and fibrous roots of the baby bok choy are most densely distributed. Applying sufficient organic material to this layer provides ample energy and nutrient release for the roots; simultaneously, this layer has good aeration, and the aerobic decomposition of straw generates a large amount of CO2 and heat, promoting root respiration and active nutrient absorption. The decomposition rate enters a rapid phase in 7-14 days, precisely coinciding with the peak nutrient demand during the rosette stage, when the baby bok choy plant's growth is at its maximum. The design of applying fertilizer in the second layer (15cm-20cm), accounting for 30%-40% of the total, is based on the following mechanism: This layer has poor aeration, the straw decomposes more slowly (taking 15-25 days to enter rapid decomposition), and the concentration of organic acids and reducing substances is lower, which will not inhibit the main root of the baby bok choy. At the same time, it provides a continuous and stable supply of nutrients during the heading stage of the baby bok choy, preventing nutrient deficiency in the later stage. The whole system forms a time-space dual-gradient synergistic fertilization system of concentrated shallow fertilization in the early stage and continuous deep fertilization in the later stage.

[0123] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for returning straw to the field to improve the soil quality of the rhizosphere of baby bok choy, characterized in that, Includes the following steps: Step S1: After drying the crop straw to the preset moisture content and crushing it, mix it with the three strains of compound pretreatment microbial agent according to the preset mass ratio, adjust the moisture content and then pile it for fermentation. When the temperature at the center of the pile reaches the preset temperature, turn the pile over and maintain fermentation until white mycelium appears on the surface of the straw and the color turns yellowish-brown to obtain the pretreated straw material. Step S2: The pretreated straw material is mixed with the rhizosphere targeted conditioner at a preset mass ratio to control the soil pH within the range of 6.5-6.8, thereby obtaining the conditioned straw material. Step S3: Before planting baby bok choy, cultivate the soil for a predetermined number of days, and apply the prepared straw material in two layers according to the predetermined amount to control the organic acid concentration in the soil 15cm-20cm below the surface to be below 50mg / kg. Rotary tillage is then used to mix the straw with the soil. Step S4: Dilute the rhizosphere activator to the preset ratio and apply it to the rhizosphere soil during the rosette and heading stages of the baby bok choy, once each during the rosette and heading stages.

2. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 1, characterized in that, In step S1, the crop straw is corn straw or rye straw; the mass ratio of the dried straw to the three-strain compound pretreatment agent is 100:1-100:5; the crop straw is dried to a moisture content of 10%-20% and pulverized to a length of 1cm-5cm; the three-strain compound pretreatment agent contains Bacillus subtilis, Trichoderma viride, and yeast, with a viable count ratio of 2:1:1 and a total viable count ≥1×10⁻⁶. 8 CFU / g.

3. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 2, characterized in that, In step S1, the moisture content is adjusted to 50%-65%; during the pile fermentation, the pile is turned when the temperature at the center of the pile reaches 55℃-65℃, and the total fermentation time is 5-10 days. When the temperature at the center of the pile is below 50℃ and the moisture content of the material is below 50%, water is added and the turning frequency is appropriately reduced to reduce heat loss and maintain the pile temperature; the moisture content of the pile is always maintained within the range of 50%-65% by adding water.

4. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 3, characterized in that, In step S1, the height of the pile is 1.0m-1.5m and the width is 1.5m-2.0m.

5. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 4, characterized in that, In step S2, the mass ratio of the pretreated straw material to the rhizosphere targeted conditioner is 100:3-100:

8.

6. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 5, characterized in that, In step S2, the soil pH regulator, micronutrient supplement, and rhizosphere probiotic community in the rhizosphere targeted conditioning agent have a mass ratio of 3:3:

4. The soil pH regulator is composed of humic acid and gypsum in a mass ratio of 3:1-5:

1. The micronutrient supplement is a chelated fertilizer containing 120g / L Ca, 40g / L Mg, 15g / L Zn, and 10g / L B. The rhizosphere probiotic community includes Bacillus amyloliquefaciens and Bacillus mucilaginosus, with a total viable count ≥1×10⁻⁶. 9 CFU / g.

7. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 6, characterized in that, In step S3, the baby bok choy is initially cultivated 7-15 days before planting, with a cultivation depth of 20cm-25cm; the total amount of conditioning straw material applied is 300kg / mu-600kg / mu.

8. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 7, characterized in that, In step S3, the two-layer application specifically involves: applying a first layer of conditioning straw material, accounting for 60%-70% of the total conditioning straw material, to a depth of 5cm-10cm below the soil surface and rotary tilling to mix it; and applying a second layer of conditioning straw material, accounting for 30%-40% of the total conditioning straw material, to a depth of 15cm-20cm below the soil surface and rotary tilling to mix it.

9. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 8, characterized in that, In step S4, the rhizosphere activation promoter contains amino acid water-soluble fertilizer, potassium humate and Bacillus subtilis metabolite extract; when using, it is diluted 200-500 times and applied by hole application or trench application, with an application depth of 5cm-10cm, and the amount applied each time is 10L / mu-20L / mu of diluted liquid.

10. The method for returning straw to the field to improve the rhizosphere soil quality of baby bok choy according to claim 9, characterized in that, In step S4, the total amino acid content of the amino acid water-soluble fertilizer is ≥100g / L; the water-soluble humic acid content of the potassium humate is ≥60g / L; and the Bacillus subtilis metabolite extract is a powder obtained by concentrating and drying the supernatant of Bacillus subtilis fermentation broth, containing lipopeptide active substances and extracellular polysaccharides.

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