Method for soil improvement based on a composite microbial inoculant / organic compost salt-alkali gradient

Abstract

The application relates to the technical field of saline-alkali soil improvement, and discloses a composite microbial agent / organic compost soil improvement method based on a saline-alkali gradient. The soil improvement method comprises the following steps: (1) detecting the soil salinity of a saline-alkali land, and dividing the saline-alkali land into one or more gradient types of saline soil, heavy saline-alkali soil, moderate saline-alkali soil and light saline-alkali soil; (2) according to the divided saline-alkali gradient type, at least one of a composite microbial agent or an organic compost preparation is selectively applied; (3) after being uniformly applied to the ground, the composite microbial agent or the organic compost preparation is ploughed into the soil and irrigated; the composite microbial agent comprises a functional bacterial flora, an organic nutrient agent and a carrier auxiliary material; the organic compost preparation is prepared by mixing crop straws, livestock and poultry manure and a carrier auxiliary material, and then subjected to aerobic fermentation and composting. The improvement method realizes differentiated and accurate improvement of soils with different saline-alkali degrees.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement technology, and in particular to a method for soil improvement based on a composite microbial agent / organic compost based on a salinity gradient. Background Technology

[0002] Soil salinization is a key obstacle to agricultural development and ecological restoration in arid and semi-arid regions worldwide. China's saline-alkali land area accounts for approximately 1% of its total land area. Ejin Banner, located at the westernmost tip of Inner Mongolia Autonomous Region in the lower reaches of the Heihe River basin, is a typical temperate continental extreme arid climate zone. Evaporation far exceeds precipitation, and coupled with intense weathering and salt deposition of parent material, this region has formed large areas of gradient saline-alkali wasteland. Severe soil salinization stress directly poisons plant roots, damages soil aggregate structure, reduces nutrient availability, greatly weakens the self-repair capacity of ecosystems, and seriously threatens regional ecological security and the sustainable development of agriculture and animal husbandry.

[0003] Traditional physical methods of soil remediation, such as irrigation to leach salt, consume large amounts of water and are unsustainable in extremely arid regions. Importing soil involves large-scale engineering projects and is costly. Chemical methods, such as applying gypsum or phosphogypsum, can reduce alkalinity by replacing sodium ions with calcium ions, but long-term application can easily lead to secondary environmental problems such as soil compaction, a drop in groundwater levels, and eutrophication. Therefore, there is an urgent need to develop economical, environmentally friendly, and sustainable saline-alkali soil remediation technologies.

[0004] Currently, biological soil improvement technologies are attracting significant attention due to their environmental friendliness and cost-effectiveness. Compost, as a high-quality organic amendment, can increase soil organic matter content, improve soil structure, enhance water and fertilizer retention capacity, and mitigate sodium ion toxicity through ion exchange and adsorption, while also providing carbon and energy sources for microorganisms. However, in extremely saline-alkali environments, the indigenous microbial community structure is limited and its functions are restricted; simply adding organic matter is insufficient to quickly initiate and maintain efficient ecological restoration. The introduction of microbial agents can compensate for this deficiency. Functional microorganisms, such as salt-tolerant Bacillus, can adapt to high-salt environments by adjusting their osmotic pressure systems, secreting organic acids to neutralize alkalinity, activating fixed nutrients, and producing plant hormones to promote root growth.

[0005] When microbial agents are applied in combination with organic compost, the microorganisms can accelerate the decomposition and humification of organic matter, while the organic matter provides a carrier and substrate for microbial colonization. The two work together to promote the formation of soil aggregates and reduce pH and electrical conductivity.

[0006] However, existing research on biological improvement of saline-alkali land still has the following obvious defects: (1) Most studies focus on specific regions or single improvement methods, lacking gradient and systematic research on soils with different salinity and alkali levels, making it difficult to form targeted and differentiated improvement schemes; (2) There is a serious lack of research on the seasonal dynamic changes of the effects of improvement measures on soil physicochemical properties, making it difficult to accurately assess the long-term stability and sustainability of the improvement effect. Summary of the Invention

[0007] The technical problem to be solved by this invention is that the existing technology has the disadvantages of poor targeting, insufficient long-term stability and sustainability. To this end, we propose a soil improvement method based on a composite microbial agent / organic compost based on a salinity gradient.

[0008] To achieve the above objectives, this application adopts the following technical solution: a soil improvement method based on a salinity gradient using a composite microbial agent / organic compost, comprising the following steps:

[0009] (1) Conduct soil salinity and alkalinity tests on saline-alkali plots and classify them into one or more gradient types, such as saline soil, severely saline-alkali, moderately saline-alkali, and slightly saline-alkali.

[0010] (2) Selectively apply at least one of compound microbial agents or organic composting agents according to the classified salinity gradient type;

[0011] (3) After applying it evenly to the surface, plow it into the soil and irrigate it;

[0012] By weight, the compound microbial agent comprises 20-40 parts of functional microbial groups, 15-30 parts of organic nutrients, and 30-65 parts of carrier excipients.

[0013] The organic compost preparation is made by mixing crop straw, livestock and poultry manure and carrier additives at a carbon-nitrogen ratio of (25-30):1 and then aerobically fermenting and maturing them.

[0014] Preferably, in step (1), the soil salinity is classified into the following gradients based on the 1:5 soil-to-water ratio conductivity:

[0015] Soil with an electrical conductivity >4 dS / m is considered saline soil.

[0016] When the soil electrical conductivity is 2-4 dS / m, it is considered severely saline-alkali.

[0017] When the soil electrical conductivity is 1-2 dS / m, it is considered moderately saline-alkaline.

[0018] When the soil electrical conductivity is <1dS / m, it is considered slightly saline-alkali.

[0019] Preferably, in step (2), when the soil is saline or severely saline-alkali, the dosage of the compound microbial agent is 30-40 kg / mu, and the dosage of the organic compost preparation is 2-3 tons / mu;

[0020] When the soil is moderately saline-alkali, the dosage of the compound microbial agent is 20-30 kg / mu, and the dosage of the organic compost preparation is 1.5-2 tons / mu;

[0021] When the soil is slightly saline-alkali, the dosage of the compound microbial agent is 10-20 kg / mu, and the dosage of the organic compost preparation is 1-1.5 tons / mu.

[0022] Preferably, the functional microbial community is composed of Bacillus subtilis, lactic acid bacteria, Saccharomyces cerevisiae, Streptomyces and photosynthetic bacteria in an effective viable count ratio of (2-4):(1-2):(1-2):(1-2):(1-2);

[0023] The organic nutrient is composed of humic acid, plant extracts and amino acids in a weight ratio of (3-5):(1-2):(1-2);

[0024] The carrier additive is a mixture of peat moss, vermiculite, biochar and diatomaceous earth in a weight ratio of (2-4):(1-2):(1-3):(1-2).

[0025] Preferably, the total number of effective viable bacteria in the compound microbial agent is not less than 2×10⁸ CFU / g.

[0026] Preferably, the crop straw is selected from at least one of corn straw or wheat straw; the livestock and poultry manure is selected from at least one of sheep manure or cow manure; the carrier auxiliary material is a mixture of peat moss, vermiculite, biochar and diatomaceous earth in a weight ratio of (2-4):(1-2):(1-3):(1-2);

[0027] The organic compost preparation has an organic matter content of not less than 45% and a total nutrient content of not less than 5%.

[0028] Preferably, in step (2), the application is performed on a cloudy day or a sunny evening when the ground temperature is between 5℃ and 35℃.

[0029] In step (3), the depth of tilling into the soil is 10-20 cm; irrigation is carried out by drip irrigation or micro-sprinkler irrigation to keep the soil moisture content at 60%-70% of the field capacity.

[0030] The technical effects and advantages of this invention are as follows:

[0031] (1) The improvement method of the present invention divides soils with different salinity gradients and selectively applies at least one of compound microbial agents or organic compost preparations according to the differences in salinity, thereby achieving differentiated and precise improvement of soils with different salinity.

[0032] (2) The improved method of the present invention highlights the rapid salt reduction and alkali adjustment advantages of the compound microbial agent under saline soil and severely saline-alkali conditions. The functional bacteria such as Bacillus subtilis in the agent secrete organic acids to neutralize alkalinity, promote the leaching of soluble salts and the redistribution of surface salts, and rapidly reduce soil electrical conductivity and pH. Under mildly saline-alkali conditions, the long-lasting water-increasing and moisture-retaining advantages of the organic compost preparation are highlighted. By increasing the organic matter content, the soil aggregate structure is improved, and the water and fertilizer retention capacity is enhanced. This avoids the inefficiency and waste of ordinary application methods and overcomes the shortcomings of the existing technology in lacking systematic and gradient research on soils with different salinity and alkali levels.

[0033] (3) In the improvement method of the present invention, the compound microbial agent and the organic compost preparation can be used in combination to achieve a dual improvement effect. On the one hand, the functional microbial community contains multiple species such as Bacillus subtilis, lactic acid bacteria, and Saccharomyces cerevisiae in a specific ratio, which work together to accelerate the decomposition and humification of organic matter and release nutrients; on the other hand, the organic compost preparation provides a carrier and carbon source for the colonization and reproduction of functional microorganisms, promotes the formation of soil aggregates, and reduces soil bulk density, which is significantly better than the improvement effect of applying microbial agents or compost alone.

[0034] (4) This invention fully considers the impact of seasonal dynamic changes on the improvement effect, and clarifies that the best application time is cloudy days or sunny evenings when the soil temperature is 5℃-35℃, avoiding the inactivation of the strain due to high temperature and strong direct sunlight. It also precisely controls the soil moisture content to 60%-70% of the field water holding capacity through drip irrigation or micro-sprinkler irrigation, which not only provides suitable water conditions for microbial metabolic activities, but also avoids salt accumulation on the surface due to flood irrigation, thus ensuring the long-term stability and sustainability of the improvement effect. Attached Figure Description

[0035] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0036] Figure 1 Soil physicochemical characteristics under different salinity gradients and microbial inoculant and compost treatments in different months;

[0037] Figure 2 Differences in soil physicochemical properties between treatments and controls under different salinity gradients;

[0038] Figure 3 The characteristic differences in soil physicochemical properties under microbial inoculant and compost treatments;

[0039] Figure 4 To illustrate the differences in physicochemical properties of soils with different salinity gradients under composting treatment;

[0040] Figure 5 The differences in physicochemical properties of soils with different salinity gradients under microbial agent treatment;

[0041] Figure 6 To illustrate the differences in the physicochemical properties of soils with different salinity gradients under different treatments;

[0042] Figure 7 The percentage changes between different treatments and the control under different salinity gradients;

[0043] Figure 8 The significant correlation between soil physicochemical properties under different treatments is shown. Detailed Implementation

[0044] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0045] It should be noted that Bacillus subtilis, lactic acid bacteria, Saccharomyces cerevisiae, Streptomyces and photosynthetic bacteria are all commercially available strains.

[0046] Bacillus subtilis can be purchased from the China General Microbiological Culture Collection Center (CGMCC), with a deposit date of 10 / 26 / 1999 and accession number CGMCC 1.2416;

[0047] Lactic acid bacteria can be purchased from the China General Microbiological Culture Collection Center (CGMCC), with a preservation date of 1 / 28 / 2002 and a preservation number of CGMCC 1.2919;

[0048] The brewing yeast can be high-activity dry yeast purchased from Angel Yeast Co., Ltd.;

[0049] Streptomyces can be Streptomyces flavus-99 purchased from Shandong Haizhou Bioengineering Co., Ltd.;

[0050] The photosynthetic bacteria can be *Rhodopseudomonas palustris* purchased from Wuhan Beileye Biomedical Technology Co., Ltd.

[0051] Preparation of compound microbial agents

[0052] The compound microbial agent is prepared by the following steps:

[0053] (1) Preparation of functional microbial community: Bacillus subtilis, lactic acid bacteria, Saccharomyces cerevisiae, Streptomyces and photosynthetic bacteria were mixed evenly in a ratio of 3:1.5:1.5:1.5:1.5, and the total effective viable count of each species was controlled to be not less than 2×10 8 CFU / g;

[0054] (2) Preparation of organic nutrients: Humic acid, seaweed extract and compound amino acid powder are mixed evenly in a weight ratio of 4:1.5:1.5;

[0055] (3) Preparation of carrier auxiliary materials: mix peat moss, vermiculite, biochar and diatomaceous earth in a weight ratio of 3:1.5:2:1.5, adjust the moisture content to 20%, and pass through an 80-mesh sieve;

[0056] (4) By weight, 30 parts of functional bacteria, 25 parts of organic nutrients and 45 parts of carrier excipients are stirred and mixed evenly under normal temperature and low humidity, and vacuum packaged to obtain the compound microbial agent.

[0057] Preparation of organic composting agents

[0058] Organic compost formulations are prepared using the following steps:

[0059] (1) Preparation of carrier auxiliary materials: Peat moss, vermiculite, biochar and diatomaceous earth are mixed in a weight ratio of 3:1.5:2:1.5, the moisture content is adjusted to 20%, and the mixture is passed through an 80-mesh sieve;

[0060] (2) Mix the crushed corn stalks, sheep manure and carrier additives evenly at a carbon-nitrogen ratio of 28:1, and add Bacillus subtilis at a ratio of 0.5×108 CFU / g;

[0061] (3) Adjust the moisture content to 55%-60%, pile it into windrows 1.5-2 meters high, and carry out aerobic fermentation;

[0062] (4) When the pile temperature rises to above 55°C, start turning the pile. Turn the pile every 5-7 days and maintain the pile temperature between 55-65°C for at least 10 days. When the pile temperature naturally drops to near the ambient temperature, the material turns blackish-brown and has no odor, the fermentation is complete. After sieving, the organic compost preparation is obtained. The organic compost preparation has an organic matter content of 50% and a total nutrient content of 5.5%.

[0063] Example 1

[0064] Soil improvement can be achieved through the following steps:

[0065] (1) Newly reclaimed land in the desert area of ​​Ejin Banner, Inner Mongolia Autonomous Region, was selected as the experimental field. The entire plot was vertically excavated to a depth of 50cm, and backfilled with soil of different salinity and alkalinity to set up four salinity gradients, namely:

[0066] Saline soil: Soil electrical conductivity > 4 dS / m;

[0067] Severe salinity: Soil electrical conductivity 2-4 dS / m;

[0068] Moderately saline-alkali soil: soil electrical conductivity 1-2 dS / m;

[0069] Slightly saline-alkali: Soil electrical conductivity <1dS / m.

[0070] (2) Microbial agent treatment: After the compound microbial agent is evenly spread on the surface of the soil with different salinity gradients, it is tilled into the soil to a depth of 15 cm for microbial agent treatment;

[0071] Among them, the compound microbial agent is applied at 35 kg / mu in saline soil; 30 kg / mu in severely saline-alkali soil; 25 kg / mu in moderately saline-alkali soil; and 15 kg / mu in slightly saline-alkali soil.

[0072] (3) The application time is in early May, on cloudy evenings when the soil temperature is above 15℃. Irrigation is done by drip irrigation to keep the soil moisture content at 75% of the field capacity.

[0073] Example 2

[0074] Soil improvement can be achieved through the following steps:

[0075] (1) Newly reclaimed land in the desert area of ​​Ejin Banner, Inner Mongolia Autonomous Region, was selected as the experimental field. The entire plot was vertically excavated to a depth of 50cm, and backfilled with soil of different salinity and alkalinity to set up four salinity gradients, namely:

[0076] Saline soil: Soil electrical conductivity > 4 dS / m;

[0077] Severe salinity: Soil electrical conductivity 2-4 dS / m;

[0078] Moderately saline-alkali soil: soil electrical conductivity 1-2 dS / m;

[0079] Slightly saline-alkali: Soil electrical conductivity <1dS / m.

[0080] (2) Composting treatment: After the organic composting agent is evenly spread on the surface of the soil with different salinity gradients, it is tilled into the soil to a depth of 15 cm for composting treatment.

[0081] Among them, the organic composting agent is applied at 3 tons / mu in saline soil; 2.5 tons / mu in severely saline-alkali soil; 2 tons / mu in moderately saline-alkali soil; and 1.5 tons / mu in slightly saline-alkali soil.

[0082] (3) The application time is in early May, on cloudy evenings when the soil temperature is above 15℃. Irrigation is done by drip irrigation to keep the soil moisture content at 70% of the field capacity.

[0083] Example 3

[0084] Soil improvement can be achieved through the following steps:

[0085] (1) Newly reclaimed land in the desert area of ​​Ejin Banner, Inner Mongolia Autonomous Region, was selected as the experimental field. The entire plot was vertically excavated to a depth of 50cm, and backfilled with soil of different salinity and alkalinity to set up four salinity gradients, namely:

[0086] Saline soil: Soil electrical conductivity > 4 dS / m;

[0087] Severe salinity: Soil electrical conductivity 2-4 dS / m;

[0088] Moderately saline-alkali soil: soil electrical conductivity 1-2 dS / m;

[0089] Slightly saline-alkali: Soil electrical conductivity <1dS / m.

[0090] (2) Compound treatment: First, the organic compost preparation is evenly spread on the surface of the land with different salinity gradients and then plowed into the soil to a depth of 15 cm for composting treatment.

[0091] One week after composting, the compound microbial agent is evenly spread on the surface of soil with different salinity gradients and then tilled into the soil again to a depth of 15 cm for microbial treatment.

[0092] Among them, the compound microbial agent is applied at 35 kg / mu in saline soil; 30 kg / mu in severely saline-alkali soil; 25 kg / mu in moderately saline-alkali soil; and 15 kg / mu in slightly saline-alkali soil.

[0093] The organic composting agent is applied at 3 tons / mu in saline soil; 2.5 tons / mu in severely saline-alkali soil; 2 tons / mu in moderately saline-alkali soil; and 1.5 tons / mu in slightly saline-alkali soil.

[0094] (3) The application time is in early May, on cloudy evenings when the soil temperature is above 15℃. Irrigation is done by drip irrigation to keep the soil moisture content at 60% of the field capacity.

[0095] Comparative Example 1

[0096] The example is basically the same as Example 1, except that no microbial treatment was performed, serving as a control example without the addition of any preparations.

[0097] Performance testing

[0098] In October, topsoil samples (0-20 cm) were collected from each treatment plot. The decrease in soil salinity and increase in organic matter were measured in Examples 1-3 compared to Comparative Example 1 under saline, severely saline-alkali, moderately saline-alkali, and slightly saline-alkali conditions. The results are shown in Table 1 below.

[0099] Table 1

[0100]

[0101] Analysis shows that the combined treatment of compound microbial agents and compost has a more significant advantage under high salinity gradients, while single compost or microbial agent treatments are more prominent under low salinity gradients.

[0102] Soil salinity and alkalinity were measured in the experimental area and control group of Ejin Banner. The experimental area was improved according to the soil improvement methods in Examples 1-3, and the control group was improved according to the soil improvement method in Comparative Example 1. The pH and electrical conductivity of the soil were measured before application, in the first year after application, and in the second year after application. The results are shown in Table 2 below.

[0103] Table 2

[0104]

[0105] By measuring the soil salinity and alkalinity of the experimental area and the control group in Ejin Banner, it was found that the simultaneous application of compound microbial agents and organic compost preparations significantly reduced soil salinity and alkalinity.

[0106] Soil salinity and alkalinity were measured in the experimental area and control group of Ejin Banner. The soil improvement methods in the experimental area were implemented according to Examples 1-3, and the soil improvement method in the control group was implemented according to Comparative Example 1. The organic carbon and total nitrogen contents of the soil were measured before application, in the first year after application, and in the second year after application. The results are shown in Table 3 below:

[0107] Table 3

[0108]

[0109] After applying a compound microbial inoculant and an organic composting agent, the soil nutrient content in the experimental area significantly increased. Data analysis showed that the compound microbial inoculant improved soil fertility by promoting the decomposition of organic materials and the release of nutrients, while the organic composting agent provided the soil with abundant organic matter and nutrient sources.

[0110] Soil salinity and alkalinity were measured in the experimental area and control group of Ejin Banner. The experimental area was improved according to the soil improvement methods in Examples 1-3, and the control group was improved according to the soil improvement method in Comparative Example 1. Spring maize was then planted in the soil, and the emergence rate, plant height, and biomass of spring maize were measured before application, in the first year after application, and in the second year after application. The results are shown in Table 4 below.

[0111] Table 4

[0112]

[0113] The growth indicators of crops in the experimental area were significantly improved after the application of compound microbial inoculants and organic compost preparations. This indicates that the method has a significant promoting effect on crop growth.

[0114] In addition, the chlorophyll content and antioxidant enzyme activity of crops in the experimental area were significantly increased, further verifying the positive effects of compound microbial agents and organic compost preparations on crop physiological health.

[0115] Soil samples were collected from the top 0-20cm layer and the bottom 20-40cm layer in July, September and October, respectively, to measure soil moisture content, soil electrical conductivity and soil pH, and the experimental results were analyzed.

[0116] like Figure 1 Soil physicochemical characteristics under different salinity gradients and microbial inoculant and compost treatments in different months are shown below:

[0117] Under saline soil gradient, microbial treatment significantly increased moisture content and reduced electrical conductivity and pH from July to September, but the effect weakened in October; compost treatment showed a similar trend, but its electrical conductivity and pH did not differ significantly between months, indicating that compost is more effective in inhibiting salt accumulation on the surface.

[0118] Under severely saline-alkali conditions, there were no significant differences in any indicators among the months for the microbial agent treatment, indicating a stable improvement effect that was superior to that of the compost treatment. Under moderately saline-alkali conditions, there were no significant differences in any of the physicochemical properties among the months for the microbial agent treatment, while the compost treatment showed significant fluctuations. Under slightly saline-alkali conditions, both treatments exhibited some degree of volatility.

[0119] Overall, microbial agents are more effective in reducing electrical conductivity and regulating pH, while compost is better at increasing moisture content. Seasonal changes significantly affect the improvement effect; environmental factors such as soil temperature and precipitation can promote microbial activity and enhance the improvement effect, indicating that it is necessary to select the appropriate time for treatment based on seasonal factors to improve the sustainability of the effect.

[0120] like Figure 2 The differences in soil physicochemical properties between different treatments and the control under different salinity gradients are shown below:

[0121] Under saline, severely saline-alkali, and moderately saline-alkali conditions, the soil moisture content of both the microbial agent and compost treatments was significantly higher than that of the control, but the difference between the two treatments was not significant. Under slightly saline-alkali conditions, the moisture content of the compost treatment was significantly higher than that of the microbial agent treatment. At each salinity gradient, the soil electrical conductivity and pH of both treatments were significantly lower than those of the control, indicating that both improvement measures can effectively reduce soil salinity and pH.

[0122] In particular, the microbial agent showed a significant advantage in reducing salinity in moderately saline conditions, with its electrical conductivity being significantly lower than that of the compost treatment and the control.

[0123] like Figure 3 The differences in soil physicochemical properties between microbial inoculant and compost treatments are shown below:

[0124] In saline soil, and severely and moderately saline-alkali environments, the two treatments had little difference in their effect on soil moisture content. However, in mildly saline-alkali environments, the compost treatment showed significantly higher moisture content, indicating that compost was more effective in increasing soil moisture. In severely and moderately saline-alkali environments, the conductivity of the microbial agent treatment was significantly lower than that of compost, showing a stronger salt-reducing advantage. In mildly saline-alkali environments, the conductivity of the compost treatment was even lower, indicating a stronger salt-reducing effect. Regarding soil pH, in the range of saline to moderately saline-alkali soil, the pH of the compost treatment was lower than that of the microbial agent, indicating that compost had a stronger ability to reduce soil alkalinity than the microbial agent.

[0125] like Figure 4 The differences in physicochemical properties of soils with different salinity gradients under composting treatment are shown below:

[0126] Under composting treatment, the four salinity gradients between soil layers at different depths showed inconsistent behavior: in saline soil and mild salinity environments, the surface soil moisture content was significantly lower than that in the lower layers; while in moderate and severe salinity environments, the surface soil moisture content was higher than that in the lower layers. The difference in soil electrical conductivity between the surface and lower layers showed a consistent trend, and the difference gradually decreased with increasing salinity gradient, indicating that composting significantly reduced salt accumulation in the lower soil layers. In saline soil, severe salinity, and mild salinity environments, the surface soil pH was significantly higher than that in the lower layers; however, in moderate salinity environments, the surface soil pH was lower than that in the lower layers.

[0127] like Figure 5 The differences in physicochemical properties of soils with different salinity gradients under microbial inoculant treatment are shown:

[0128] Under microbial treatment, all four salinity gradients at different soil depths showed consistent results: the surface soil moisture content was significantly lower than that of the underlying layers. Soil electrical conductivity varied between soil layers at different salinity gradients. In saline soils, the difference between the surface and underlying layers was not significant; in severely and moderately saline-alkali soils, the surface soil electrical conductivity was significantly higher than that of the underlying layers; in slightly saline-alkali soils, the surface soil electrical conductivity was lower than that of the underlying layers. In saline, moderate, and slightly saline-alkali soils, the surface soil pH was lower than that of the underlying layers, while in severely saline soils, the underlying layers had a slightly higher pH than the surface layers.

[0129] like Figure 6 The differences in physicochemical properties of soils under different treatments and salinity gradients are shown below:

[0130] The study found that the microbial agent consistently regulated soil moisture across different salinity gradients, while compost had inconsistent effects on soil layers within each gradient. The compost treatment exhibited completely consistent changes in soil electrical conductivity across soil layers, but the microbial agent treatment showed inconsistent effects on soil layers within each salinity gradient. Furthermore, the microbial agent and compost treatments had different effects on soil pH across different salinity gradients, indicating that the effects of microbial agents and compost on soil pH differ across different salinity gradient soil environments.

[0131] like Figure 7 The percentage changes in different treatments under different salinity gradients compared to the control are shown below:

[0132] The soil moisture content increased overall under the action of microbial agents and compost, and the rate of change of soil moisture content gradually decreased as the salinity gradient decreased, indicating that the microbial agent and compost treatments had a greater effect on increasing the soil moisture content in soils with higher salinity and alkalinity. The rate of change of soil electrical conductivity showed that both microbial agents and compost significantly reduced soil salinity. The analysis of the rate of change of soil pH showed that both treatments had a lowering effect on soil pH.

[0133] like Figure 8 The significant correlations between soil physicochemical properties under different treatments are shown:

[0134] Under microbial treatment, soil moisture content was significantly negatively correlated with electrical conductivity and pH under saline soil conditions, while electrical conductivity was significantly positively correlated with pH. Under severe saline-alkali conditions, electrical conductivity was significantly negatively correlated with pH, ​​while under mild saline-alkali soil conditions, electrical conductivity was significantly negatively correlated with pH.

[0135] Under composting treatment, soil moisture content and pH were significantly negatively correlated in saline-alkali soils, while moisture content and pH were significantly positively correlated in slightly saline-alkali soils. Electrical conductivity and pH were significantly negatively correlated in slightly saline-alkali soils, while electrical conductivity and pH were significantly positively correlated in saline and moderately saline-alkali soils.

[0136] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for soil improvement based on a salinity gradient using a composite microbial agent / organic compost, characterized in that, Includes the following steps: (1) Conduct soil salinity and alkalinity tests on saline-alkali plots and classify them into one or more gradient types, such as saline soil, severely saline-alkali, moderately saline-alkali, and slightly saline-alkali. (2) Selectively apply at least one of compound microbial agents or organic composting agents according to the classified salinity gradient type; (3) After applying it evenly to the surface, plow it into the soil and irrigate it; By weight, the compound microbial agent comprises 20-40 parts of functional microbial groups, 15-30 parts of organic nutrients, and 30-65 parts of carrier excipients. The organic compost preparation is made by mixing crop straw, livestock and poultry manure and carrier additives at a carbon-nitrogen ratio of (25-30):1 and then aerobically fermenting and maturing them.

2. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, In step (1), based on the 1:5 soil-to-water ratio electrical conductivity, the soil salinity is divided into the following gradients: Soil with an electrical conductivity >4 dS / m is considered saline soil. When the soil electrical conductivity is 2-4 dS / m, it is considered severely saline-alkali. When the soil electrical conductivity is 1-2 dS / m, it is considered moderately saline-alkaline. When the soil electrical conductivity is <1dS / m, it is considered slightly saline-alkali.

3. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, In step (2), when the soil is saline or severely saline-alkali, the dosage of the compound microbial agent is 30-40 kg / mu, and the dosage of the organic compost preparation is 2-3 tons / mu. When the soil is moderately saline-alkali, the dosage of the compound microbial agent is 20-30 kg / mu, and the dosage of the organic compost preparation is 1.5-2 tons / mu; When the soil is slightly saline-alkali, the dosage of the compound microbial agent is 10-20 kg / mu, and the dosage of the organic compost preparation is 1-1.5 tons / mu.

4. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, The functional microbial community is composed of Bacillus subtilis, lactic acid bacteria, Saccharomyces cerevisiae, Streptomyces and photosynthetic bacteria in an effective viable count ratio of (2-4):(1-2):(1-2):(1-2):(1-2); The organic nutrient is composed of humic acid, plant extracts and amino acids in a weight ratio of (3-5):(1-2):(1-2); The carrier additive is a mixture of peat moss, vermiculite, biochar and diatomaceous earth in a weight ratio of (2-4):(1-2):(1-3):(1-2).

5. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, The total number of viable bacteria in the compound microbial agent is not less than 2×10⁻⁶. 8 CFU / g.

6. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, The crop straw is selected from at least one of corn straw or wheat straw; the livestock and poultry manure is selected from at least one of sheep manure or cow manure; the carrier auxiliary material is a mixture of peat moss, vermiculite, biochar and diatomaceous earth in a weight ratio of (2-4):(1-2):(1-3):(1-2); The organic compost preparation has an organic matter content of not less than 45% and a total nutrient content of not less than 5%.

7. The method for soil improvement based on salinity gradient using composite microbial agents / organic compost according to claim 1, characterized in that, In step (2), the application is performed on cloudy days or sunny evenings when the ground temperature is between 5℃ and 35℃. In step (3), the depth of tilling into the soil is 10-20 cm; irrigation is carried out by drip irrigation or micro-sprinkler irrigation to keep the soil moisture content at 60%-70% of the field capacity.

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