Saline-alkali soil improver with carbon and nutrient efficiency and application thereof

Abstract

The application discloses a saline-alkali soil modifier and application thereof, which takes into account soil carbon increase and capacity expansion and nutrient increase. Surface soil samples are collected to detect salt and alkali content and basic fertility conditions of the soil. A salt washing and alkali reduction method is determined according to the soil salt and alkali conditions. Then, a mixture of fermented cow manure and sheep manure, straw biochar, humic acid, oxalic acid, chitin, urea and microbial inoculants is differentially applied according to soil texture and carbon increase and fertility improvement targets. The mixture is mixed with the surface soil and covered with a film to preserve soil moisture and increase temperature. After 30-80 days, conventional base fertilizer is applied to plant salt-tolerant crops, or salt-tolerant green manure is planted for one season before planting crops. The green manure and crop straw are fully crushed and returned to the field. According to the soil fertility target, the above steps are recycled.

Description

Technical Field

[0001] This invention belongs to the field of agriculture and ecology, specifically relating to a method for increasing carbon volume and restoring fertility in saline-alkali soil, and particularly to a saline-alkali soil conditioner that combines increasing soil carbon volume and enhancing nutrient efficiency and its application. Background Technology

[0002] Saline-alkali land is a global agricultural and ecological problem. As part of an ecosystem, its unique soil physicochemical and biological properties often produce unusual ecosystem material and energy cycling processes, leading to the waste of agricultural resources and a fragile ecological environment.

[0003] Soil salinity and alkalinity, along with their secondary structural and nutrient deficiencies, are key constraints on improving the quality and productivity of saline-alkali land. The difficulty in fertilizing saline-alkali land lies in the fact that high levels of basic ions, alkalinity, and pH in the soil cause the disintegration of large aggregates, resulting in a loss of physical protection for the soil organic carbon encapsulated within them. This leads to severe organic carbon mineralization and nutrient depletion, resulting in low nutrient pool construction efficiency. Therefore, for the rapid maturation and fertilization of saline-alkali cultivated land and wasteland (grassland), it is crucial to develop a comprehensive method that utilizes biological and agronomic techniques to achieve a combined effect of carbon increase, nitrogen retention, and phosphorus activation. This method is of great significance for improving the fertility level and increasing the productivity of saline-alkali land. Compared with existing technologies, this method has advantages such as rapid organic matter formation rate, strong stability, short fertilization cycle, high water and nutrient utilization rate.

[0004] Chinese invention CN202110243542.1 discloses a method for rapidly improving and enriching severely saline-alkali land, including digging a main drainage ditch and a sub-drainage ditch, connecting the sub-drainage ditch to the main drainage ditch through a water pipe, and injecting water into the severely saline-alkali land to soak the fields. This method can effectively solve the problem that the current method of improving and treating severely saline-alkali land usually involves water irrigation and salt removal.

[0005] Chinese invention CN202010395355.0 discloses a lactic acid bacteria compound preparation for improving saline-alkali soil. The lactic acid bacteria compound preparation is composed of Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus bulgaricus, Saccharomyces boulardii, and Bacillus subtilis in a certain mass ratio, which can effectively improve soil porosity and reduce soil soluble salt content and pH.

[0006] Chinese invention CN201610547143.3 discloses a soil conditioner for rapid fertilization of severely saline-alkali land and its improvement method. The conditioner is composed of flue gas desulfurization gypsum, magnetized fly ash, cellulose-acrylamide, humic acid, polyhydroxy phosphate, chitosan, calcium nitrate, N-29 methylene diurea, pumice powder, etc., and is suitable for the improvement of severely saline-alkali land with low treatment cost.

[0007] Chinese invention CN201510442132.4 discloses a method for biological composting of straw using Lactobacillus casei as a composting agent, which includes adding Lactobacillus casei as a composting agent. The composting agent consists of a compound microbial agent, Ophiopogon japonicus, rapeseed pollen, and Scenedesmus tetrapoda. This method can significantly reduce soil salinity and promote carbon enrichment and fertilization when applied to saline-alkali land.

[0008] Chinese invention CN109548448A discloses a method for improving the fertility of newly reclaimed saline-alkali land, which includes steps such as making farmyard manure, selecting salt-tolerant rice varieties, testing the soil composition of saline-alkali land, and rice cultivation management. In view of the shortcomings of existing saline-alkali land engineering improvement methods, it uses local materials and returns agricultural waste to the field after mixing and fermenting it with manure.

[0009] Based on the above intellectual property feedback, current methods for addressing the nutrient deficiency and difficulty in restoring fertility in saline-alkali land mainly involve the input of organic materials, waste such as straw and pond mud, combined with microorganisms to promote nutrient expansion. While these methods have shown some effectiveness, they suffer from problems such as large usage, low efficiency, high losses, high costs, and weak sustainability. The underlying reason is the lack of consideration for the balance between the activation and utilization of exogenous nutrients in saline-alkali land and their preservation and enhancement. The root cause lies in insufficient attention to the coordination between soil aggregation and stabilization and mineralization decomposition processes. There is an urgent need for a method to improve the fertility and efficiency of saline-alkali land that balances nutrient activation and enhancement with capacity expansion, and is adapted to soil type and climate conditions, in order to achieve a balanced and efficient utilization of multiple nutrient sources and reservoirs. Summary of the Invention

[0010] Technical problem solved: This invention comprehensively considers the types, transformation and balance characteristics of exogenous materials for saline-alkali land improvement, and adapts to factors such as soil salinity, texture and meteorological conditions. It proposes a saline-alkali land conditioner and its application that takes into account both soil carbon expansion and nutrient efficiency enhancement, breaking through a series of problems such as high cost, long cycle, large loss and low nutrient efficiency of traditional saline-alkali land improvement.

[0011] Technical solution: A saline-alkali land conditioner that combines soil carbon expansion and nutrient enhancement, consisting of 35-40 parts fermented cow manure, 35-40 parts fermented sheep manure, 20-30 parts straw biochar, 1-1.5 parts humic acid, 0.3-0.6 parts oxalic acid, 0.5-0.8 parts chitin, 0.4-0.8 parts urea, and 0.2-0.5 parts microbial inoculant.

[0012] The fermented cow manure (dry basis) has an organic matter content ≥14 wt.%, nitrogen content ≥0.35 wt.%, and salt content <5 g / kg; the fermented sheep manure (dry basis) has an organic matter content ≥30 wt.%, nitrogen content ≥0.6 wt.%, and salt content <6 g / kg; the straw biochar is made from corn or wheat straw as raw material, which is thermally cracked at 270–330℃ to produce porous biochar with a pH <8.5 and a salt content <8 g / kg; the humic acid is in powder form, passes through a 60–100 mesh sieve, has an effective content ≥80 wt.%, organic matter ≥85 wt.%, pH <6, and water content <10 wt.%; the oxalic acid is in colorless and transparent powder form, passes through a 60–80 mesh sieve, has an effective content ≥99.5 wt.%, and SO42- %... 2- +Cl - <0.2wt.%, water content <2wt.%; the chitin is a white powder with a degree of deacetylation ≥92%, viscosity <100mpa·s, effective content ≥99wt.%, water content <5wt.%, and nitrogen content ≥5.5wt.%; the urea is a powder that passes through a 60-100 mesh sieve, with a nitrogen content ≥46wt.%, biuret content <0.5wt.%, and water content <0.3wt.%; the microbial agent is a compound agent composed of Aspergillus penicillioides, Aspergillus proliferans and Mortierella alpina, Mortierella exigua, with an effective ingredient ≥75wt.% and an effective viable count ≥10 billion / gram.

[0013] The application of the soil conditioner involves the following steps: collecting soil samples from the top 0-20cm layer and measuring their salinity, pH, organic matter, and texture; determining a suitable method for leaching and reducing alkali based on soil salinity and pH; applying the conditioner differentially according to soil texture and carbon enrichment goals, mixing it with the topsoil, and then covering it with a film to retain moisture and increase temperature for 30-80 days; applying conventional base fertilizer and planting salt-tolerant crops, or planting a season of salt-tolerant green manure before planting crops; turning the green manure back into the field during the flowering period; and crushing and returning all the straw to the field after crop harvest. The above steps are repeated according to the soil enrichment goals.

[0014] When the soil salinity > 3 g / kg and pH ≤ 8.5, irrigation is carried out to leach salts. A salinity sensor is buried at a depth of 20 cm below the ground surface, and the intermittent irrigation method is adopted, with each irrigation being 5 cm. When the soil salinity ≤ 3 g / kg threshold, irrigation is stopped; when pH > 8.5, gypsum CaSO4·2H2O is applied and mixed with the surface soil, and then irrigation is carried out to leach salts. A salinity sensor and a pH sensor are buried at a depth of 20 cm below the ground surface, and the intermittent irrigation method is adopted, with each irrigation being 5 cm. When the soil salinity ≤ 3 g / kg and pH ≤ 8.5 threshold, irrigation is stopped; when pH > 10, the gypsum application rate is 1000 - 1500 kg / mu, when 9 < pH ≤ 10, the gypsum application rate is 500 - 1000 kg / mu, when 8.5 < pH ≤ 9, the gypsum application rate is 200 - 500 kg / mu.

[0015] It is set that for every 1 g / kg increase in the organic matter of the surface soil, when the soil texture is sandy soil, 900 - 1100 kg / mu of the above mixture is applied, when the soil texture is loamy soil, 750 - 900 kg / mu of the above mixture is applied, and when the soil texture is clayey soil, 600 - 750 kg / mu of the above mixture is applied.

[0016] The mixture is directly applied to the soil, or granulated in a fertilizer granulator and then applied to the soil. The particle diameter is 1 - 3 mm. A rotary tiller is used to mix it with the surface soil, and then a film is covered to conserve moisture and increase temperature; when the average daily temperature ≥ 20 °C, planting starts 30 - 40 days after film covering; when the average daily temperature is 10 - 20 °C, planting starts 40 - 60 days after film covering; when the average daily temperature < 10 °C, planting starts 60 - 80 days after film covering.

[0017] The salt - tolerant crops are rice, barley, rapeseed, sunflower, beet or sorghum. After the crops are harvested, the straw is completely粉碎 and returned to the field; the salt - tolerant green manure is sesbania, ryegrass, sweet sorghum, alfalfa or hairy vetch. When in the full - bloom stage, the green manure is completely turned and pressed into the field.

[0018] The recycling is as follows: when the average salinity of the surface soil < 2 g / kg, it is recycled once every 4 - 6 years; when the average salinity of the surface soil is 2 - 4 g / kg, it is recycled once every 3 - 4 years; when the average salinity of the surface soil > 4 g / kg, it is recycled once every 2 - 3 years.

[0019] Beneficial effects: (1) Saline - alkali obstacles are reduced. Through irrigation or applying gypsum, the soil salinity and alkalinity are rapidly reduced to below a certain threshold, effectively preventing the disintegration of saline - alkali land aggregates and providing suitable soil conditions for promoting soil aggregation and stability.

[0020] (2) Balancing soil fertility and efficiency. Cow manure and nutrients are used together. Cow manure has a high content of aromatic carbon and phenolic carbon, as well as a high ratio of hydrophobic carbon to hydrophilic carbon (HB / HI), making it difficult to decompose and thus beneficial for increasing soil carbon. Sheep manure, on the other hand, is easy to decompose and is beneficial for decomposition and release and crop absorption. By using a reasonable ratio, both crop fertility and soil fertility are taken into account.

[0021] (3) Aggregation promotes stability. Aspergillus and Mortierella fungi promote the transformation of soil aggregates <0.106 mm to >0.25 mm. Humic acid and chitin make the newly formed soil aggregates more stable, especially promoting the formation of large aggregates. The two work together to increase the formation rate of large aggregates by 2 to 7 times.

[0022] (4) Nutrient loss reduction and retention. Biochar loosens the soil, accelerates salt leaching, and inhibits nitrification, while increasing ammonium nitrogen adsorption by 0.2–0.8 mg / kg; oxalic acid can rapidly lower soil pH, reduce ammonia volatilization loss in alkaline soils, activate soil phosphorus, and promote the formation of insoluble bound Ca2+. 10 -P and Ca8-P are converted to water-soluble forms, improving phosphorus utilization.

[0023] (5) Multi-faceted synergistic effect: This method integrates multiple means such as irrigation management, external enhancement, biological promotion, and agronomic synergy. It has a compound effect of reducing salinity and alkalinity barriers, promoting the formation and stability of aggregates, increasing carbon, conserving nitrogen, and activating phosphorus. The organic matter increase rate is increased by 30 to 50 percentage points, nitrogen loss reduction and efficiency increase by more than 15 percentage points, and phosphorus utilization efficiency is increased by 20 to 30 percentage points. It has a prominent synergistic effect of irrigation and salt washing, internal carbon stabilization, biological enhancement, and planting management. Attached Figure Description

[0024] Figure 1 Technical principle diagram;

[0025] Figure 2 The content of light and heavy organic carbon in soil at maize harvest time under different experimental treatments;

[0026] Figure 3 Mineralization rate of organic carbon in organic materials under different salinity gradients (WN1, WN2, WN3, and WN4 represent different types of organic materials; CK, MS, and HS represent slightly, moderately, and moderately saline-alkali land, respectively).

[0027] Figure 4 Grading of soil water-stable aggregates under different salinity gradients and organic material application (WN1, WN2, WN3, and WN4 represent different organic material types; CK, MS, and HS represent slightly, moderately, and moderately saline-alkali land, respectively).

[0028] Figure 5Corn yield and nitrogen and phosphorus use efficiency under the application of various organic materials (OM1, OM2 and OM3 represent different amounts of the same organic material). Detailed Implementation

[0029] The following specific embodiments are further illustrations of the present invention, but do not imply that the scope of the invention is limited to the examples given. The present invention breaks through the traditional method of saline-alkali land fertilization relying on "single, one-time, large-scale input": First, irrigation is used to leach salt and reduce alkalinity, creating a soil environment conducive to the stability and aggregation of organic carbon; second, a certain ratio of organic materials from different sources, considering both long-term and fast-acting effects, is introduced; third, materials such as oxalic acid, humic acid, chitin, biochar, and microbial agents are compounded to accelerate the formation and stabilization of aggregates, reduce nitrogen leaching, and adjust acidity to activate phosphorus; finally, the "carbon activation" effect of planting salt-tolerant green manure / crops and returning green manure and straw to the field accelerates the turnover and assimilation of organic carbon. Through the above comprehensive effects, the problems of high cost, long cycle, large loss, and low nutrient efficiency in saline-alkali land fertilization are overcome.

[0030] Example 1:

[0031] The experimental plot was a moderately saline-alkali barrier farmland in the Hetao Irrigation District of Ningxia. The average soil salinity (0-20cm) was 2.71 g / kg, pH was 8.33, average organic matter content was 8.95 g / kg, total nitrogen was 0.48 g / kg, available nitrogen was 41.6 mg / kg, and available phosphorus was 13.1 mg / kg. Location: Jiaoji Village, Qukou Township, Pingluo County, Shizuishan City, Ningxia. Field plots were established starting in May 2022, with plot dimensions of 5m × 10m. The trial period was from April 5th to September 11th, 2022. The maize variety used was SN211, a dual-purpose grain and forage variety, harvested as maize silage, and the preceding crop was maize. The main implementation steps are as follows:

[0032] (1) Experimental site preparation: On April 5th, the experimental site was uniformly leveled, plowed, and rotary tilled to ensure the consistency of soil properties. Then, artificial plots were constructed, each with an area of ​​50m². 2 (5m×10m), with small ditches separating the residential areas.

[0033] (2) Organic material preparation: Nine types of organic materials were set up, with a total of 11 treatments, as detailed below:

[0034] CK0: No fertilizer used;

[0035] CK1: Contains no organic materials, uses conventional chemical fertilizers;

[0036] NF: Fermented cow manure (containing 15.4% organic matter, 0.42% nitrogen, and 3.8g / kg salt);

[0037] YF: Fermented sheep manure (containing 33.7% organic matter, 0.66% nitrogen, and 5.4g / kg salt);

[0038] BC: Corn stalk biochar (45.1% carbon, pH 8.3, salt content 6.7 g / kg);

[0039] NY1: 38 parts fermented cow manure + 38 parts fermented sheep manure + 0.5 parts urea;

[0040] NY2: 38 parts fermented cow manure + 22 parts corn stalk biochar + 0.5 parts urea;

[0041] NY3: 38 parts fermented sheep manure + 22 parts corn stalk biochar + 0.5 parts urea;

[0042] NY4: 38 parts fermented cow manure + 38 parts fermented sheep manure + 22 parts corn stalk biochar + 0.5 parts urea;

[0043] NY5: 38 parts fermented cow manure + 38 parts fermented sheep manure + 22 parts corn stalk biochar + 1 part humic acid + 0.5 parts urea;

[0044] NY6: 38 parts fermented cow manure + 38 parts fermented sheep manure + 22 parts corn stalk biochar + 1 part humic acid + 0.4 parts oxalic acid + 0.5 parts urea.

[0045] (3) Material application: Based on the application level of 500 kg C / mu in the 0-20cm tillage layer, calculate the amount of organic material applied in each treatment. The amount of organic material applied per mu is between 1110 and 5620 kg / mu. On April 9, after the above materials are mixed evenly, they are spread in the field and mixed with the surface soil. Then, they are covered with black film to increase the temperature and retain moisture for cultivation.

[0046] (4) Corn Planting: On May 20th, the plastic film was removed, and conventional fertilizers (monoammonium phosphate + urea as base fertilizer, and urea as top dressing) were applied before corn sowing. Wide and narrow rows were used, with a row spacing of 1m for wide rows and 40cm for narrow rows, and a plant spacing of 20cm. A hand-push seeder was used for sowing. Soil samples were collected before the start of the experiment and after harvest to determine soil salinity, pH, organic matter, water-soluble organic carbon, recombinant organic carbon, light recombinant organic carbon, available nitrogen, and available phosphorus. Corn was harvested on September 11th using the silage method, and the fresh and dry weight of corn biomass was measured.

[0047] Table 1 Soil physicochemical properties after maize harvest

[0048]

[0049] The physicochemical properties of the top 0–20 cm soil layer after maize harvest are shown in Table 1. It can be seen that the soil salinity differences among the treatments were small, with the lowest pH in treatment NY6, while the differences in the other treatments were not significant. This is closely related to the addition of oxalic acid in this treatment. In terms of soil organic matter content, treatments NY5 and NY6 had the highest organic matter content, significantly higher than treatments CK0, CK1, NF, and BC. Furthermore, treatment NY6 also had the highest content of water-soluble organic carbon and available phosphorus, and a relatively high content of available nitrogen. Its organic matter, water-soluble organic carbon, and available phosphorus were significantly higher than those in treatments NY3, NY4, and NY5. The contents of recombinant and lightly recombinant organic carbon in the soil of different treatments are shown in Table 1. Figure 2 As shown, treatments NY4, NY5, and NY6 significantly increased the light organic carbon (LOC) content in the soil. Compared with the single application of cow manure, sheep manure, or biochar, treatment NY6 increased LOC by 21.0%–31.7%, and the LOC content in NY6 was higher than that in treatments NY3, NY4, and NY5, indicating an improvement in soil fertility and nutrient storage capacity. In conclusion, treatment NY6 has the best effect on increasing total soil organic carbon, the proportion of LOC, and nitrogen and phosphorus nutrient storage capacity, and compared with NY3, NY4, and NY5, the components of NY6 exhibit a stronger synergistic effect.

[0050] Example 2:

[0051] Slightly saline-alkali land in the Hetao Irrigation District of Ningxia. The average soil salinity in the topsoil layer (0-20 cm) was 1.46 g / kg, pH was 8.26, average organic matter content was 11.32 g / kg, and total nitrogen was 0.53 g / kg. Location: Baofeng Village, Baofeng Town, Pingluo County, Shizuishan City, Ningxia. Surface soil samples were collected in August 2022, air-dried, ground, and sieved through a 2 mm sieve for later use. An indoor culture method was used, setting up three salinity gradients (slight, moderate, and severe) to study the changes in soil organic carbon, organic nitrogen mineralization, and soil aggregates under different salinity gradients. The indoor culture experiment lasted from December 15, 2022 to April 30, 2023, for a total of 120 days. The main implementation steps are as follows:

[0052] (1) Soil sample preparation: The air-dried and ground soil was divided into three treatments according to the salinity gradient: light (CK, i.e., 1.46 g / kg original soil), medium (MS, 3.0 g / kg) and heavy (HS, 5.0 g / kg). The salinity was higher than the background level. NaCl and Na2SO4 were added to the soil in a 1:1 ratio.

[0053] (2) Preparation of Improved Materials: Four types of improved materials were prepared, namely WN1 (36 parts fermented cow manure + 36 parts fermented sheep manure + 21 parts corn stalk biochar + 1 part humic acid + 0.4 parts oxalic acid + 0.5 parts urea), WN2 (36 parts fermented cow manure + 36 parts fermented sheep manure + 21 parts corn stalk biochar + 1 part humic acid + 0.4 parts oxalic acid + 0.5 parts urea + 0.6 parts chitosan), WN3 (36 parts fermented cow manure + 36 parts fermented sheep manure + 21 parts corn stalk biochar + 1 part humic acid + 0.4 parts oxalic acid + 0.5 parts urea + 0.4 parts microbial inoculant), and WN4 (36 parts fermented cow manure + 36 parts fermented sheep manure + 21 parts corn stalk biochar + 1 part humic acid + 0.4 parts oxalic acid + 0.5 parts urea + 0.6 parts chitosan + 0.4 parts microbial inoculant (Aspergillus)). (0.1 portions each of penicillioides, Aspergillus proliferans, Mortierella alpina, and Mortierella exigua).

[0054] (3) Cultivation Experiment: The above-mentioned improved material was mixed with 150g of soil with different salinities at a dosage of 500kg C / mu, and then placed in 1000mL Mason flasks. The soil moisture content was adjusted to 70% of field capacity (i.e., 22.5mL of deionized water was added per 150g of soil) and cultivated in an incubator at 25℃. The soil moisture in each Mason flask was replenished periodically with a dropper to maintain a fixed moisture content. The first sampling was carried out after the activation period (15 days), and thereafter, sampling was carried out every 15 days. Each treatment was set up with 18 replicates. Destructive sampling was used, and 6 samples were taken, with 3 replicates for each sample. The soil organic carbon and organic nitrogen content were measured at each sampling to calculate the soil organic carbon and nitrogen mineralization rate. At the same time, the cultivated soil samples were wet-sieved using a granulation sieve instrument to determine the water-stable aggregates.

[0055] The mineralization rate of soil organic carbon at different time periods under different salinity gradients is as follows: Figure 3 As shown in the figure, organic carbon mineralization mainly occurs in the first 30 days. With increasing soil salinity, the rate of soil organic carbon mineralization decreases significantly. For example, the average carbon mineralization rates (within the first 60 days) of organic materials in lightly, moderately, and severely saline-alkali lands are 14.57, 10.32, and 8.04 mg / (kg·d), respectively. Looking at the differences between different materials, taking moderately saline-alkali land as an example, the average carbon mineralization rates (within the first 60 days) of WN1, WN2, WN3, and WN4 are 11.9, 10.6, 10.1, and 8.6 mg / (kg·d), respectively. Overall, under the same salinity gradient, WN4 exhibits the lowest carbon mineralization rate, which is also observed in lightly and severely saline-alkali lands, indicating that WN4 organic materials have the lowest rates of organic carbon mineralization and carbon loss.

[0056] Aggregates are individual soil particles (including soil microaggregates) formed through coagulation and cementation. The content of aggregates >0.25 mm is an important indicator of soil water and fertilizer storage capacity, nutrient pool capacity, and pore structure. The classification of soil water-stable aggregates under different salinity gradients after the incubation period is as follows: Figure 4 As shown in the figure, when the soil salinity does not exceed 3 g / kg, compared with WN1, the addition of other organic materials significantly increased the content of aggregates >0.25 mm, especially in the WN4 treatment. For severely saline-alkali land (salt 5 g / kg), compared with WN1, the addition of other organic materials did not significantly increase the content of aggregates >0.25 mm, indicating that the formation period of large aggregates in severely saline-alkali land is longer. Taking severely saline-alkali land at 3 g / kg as an example, comparing different materials with the same salinity gradient, it was found that the proportions of aggregates >0.25 mm in WN1, WN2, WN3, and WN4 were 11.27%, 18.49%, 19.28%, and 37.80%, respectively. WN4 had the highest proportion of large aggregates, and the same trend was observed in slightly saline-alkali land, indicating that WN4 is more conducive to promoting the formation and stabilization of aggregates >0.25 mm.

[0057] Example 3:

[0058] The experimental plot was located in the moderately saline-alkali land of the Hetao Plain in Inner Mongolia. The topsoil (0-20cm) of the experimental plot had a salinity of 3.3-5.1 g / kg, a pH of 8.56, an average organic matter content of 9.65 g / kg, total nitrogen of 0.38 g / kg, available nitrogen of 35.8 mg / kg, and available phosphorus of 9.82 mg / kg. The soil texture was sandy loam. Field plots were established from May to September 2023, with each plot measuring 10m × 50m. Five treatments were set up, planting maize of variety M751 using drip irrigation with mulch. Location: Minjian Village, Toudaoqiao Town, Hangjinhou Banner, Bayannur City, Inner Mongolia. The main implementation steps are as follows:

[0059] (1) Experimental site preparation: On March 26, the experimental site was uniformly leveled, plowed, and rotary tilled to ensure soil homogeneity. Then, artificial trenches were dug to construct plots, each with an area of ​​500m². 2 (10m × 50m). (4)

[0060] (2) Preparation of organic materials: 37 parts of fermented cow manure, 37 parts of fermented sheep manure, 23 parts of corn straw biochar, 1 part of humic acid, 0.5 parts of oxalic acid, 0.5 parts of urea, 0.6 parts of chitin, and 0.4 parts of microbial agent are mixed evenly and then extruded and granulated to a particle size of 2-3 mm.

[0061] (3) Application of organic materials: Five treatments were set up in the experiment, namely CK0 (planting without fertilizer), CK1 (planting with conventional fertilizer), OM1 (200 kg C / mu input), OM2 (400 kg C / mu input) and OM3 (600 kg C / mu input). After the equivalent amount of organic materials were applied to the soil, they were mechanically tilled and mixed, and the surface was covered with black film to keep warm and increase moisture.

[0062] (4) Corn sowing: On April 24, conventional fertilizer was applied and corn was sown after the plastic film was removed. Mechanical sowing was used, with wide and narrow rows. The wide rows had a row spacing of 1m, the narrow rows a row spacing of 40cm, and the plant spacing was 20cm. Soil samples were collected before and after the experiment to determine salinity, pH, organic matter, available nitrogen, available phosphorus, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN). Corn yield was also measured simultaneously, and the apparent utilization rates of nitrogen and phosphorus nutrients were calculated.

[0063] Table 2 Soil physicochemical properties before and after maize planting.

[0064]

[0065] Table 2 shows the physicochemical properties of the top 0–20 cm soil layer measured before and after the experiment. Overall, the soil salinity and pH of treatments CK0 and CK1 were higher than those of treatments OM1, OM2, and OM3, while the contents of available nitrogen, available phosphorus, and microbial biomass carbon and nitrogen were lower. This indicates that the input of organic materials significantly improved the soil physicochemical properties and increased the soil carbon and nitrogen capacity. Comparison of treatments OM1, OM2, and OM3 shows that the higher the amount of organic materials used, the higher the contents of soil organic carbon, microbial biomass carbon, and nitrogen. However, considering the marginal benefits of organic material application and soil organic matter and other nutrient indicators, the difference between treatments OM2 and OM3 was not significant. Therefore, an input of 400 kg C per mu (treatment OM2) had the best effect. This means that when the input exceeds 400 kg C / mu, the effect on increasing soil carbon and nitrogen nutrient capacity weakens. Therefore, the recommended optimal input is 400 kg C / mu.

[0066] Corn yield and nitrogen and phosphorus utilization rate under different organic material application rates, such as Figure 5 As shown in the figure, corn yield increases with increasing organic material usage; the OM3 treatment yielded 864 kg / mu of corn kernels. Comparing nitrogen and phosphorus utilization rates under different material usage levels, the OM2 treatment showed the best nitrogen and phosphorus utilization rates, reaching 54.3% and 9.55% respectively. Nitrogen and phosphorus utilization rates tended to stabilize with increasing material usage. In conclusion, the above-mentioned organic material composition ratio is recommended, and an application rate of 400 kg C / mu is suggested for optimal fertilization effect and nutrient utilization efficiency.

Claims

1. The application of a saline-alkali soil improver that takes into account soil carbonation expansion and nutrient efficiency in the planting of corn M751 in moderate saline-alkali soil, characterized in that, The soil salinity of the 0-20 cm plough layer of the moderate saline-alkali land is 3.3-5.1 g / kg, the pH is 8.56, the average organic matter content is 9.65 g / kg, the total nitrogen is 0.38 g / kg, the alkali-hydrolyzable nitrogen is 35.8 mg / kg, the available phosphorus is 9.82 mg / kg, and the texture is sandy loam; the modifier is composed of 37 parts of fermented cow manure, 37 parts of fermented sheep manure, 23 parts of corn straw biochar, 1 part of humic acid, 0.5 part of oxalic acid, 0.5 part of urea, 0.6 part of chitin, and 0.4 part of microbial agent; the dry basis organic matter content of the fermented cow manure is ≥14 wt .%, the nitrogen content is ≥0.35 wt .%, and the salt content is <5 g / kg; the dry basis organic matter content of the fermented sheep manure is ≥30 wt .%, the nitrogen content is ≥0.6 wt .%, and the salt content is <6 g / kg; the corn straw biochar is porous biochar generated by heat cracking of corn straw as raw material at 270-330 ℃, the pH is <8.5, and the salt content is <8 g / kg; the humic acid is in powder form, passes through a 60-100 mesh sieve, and has an effective content of ≥80 wt .%, an organic matter content of ≥85 wt .%, a pH of <6, and a water content of <10 wt .%; the oxalic acid is colorless and transparent in powder form, passes through a 60-80 mesh sieve, and has an effective content of ≥99.5 wt .%, SO4 2- +Cl - <0.2 wt .%, and a water content of <2 wt .%; the chitin is white in powder form, has a degree of deacetylation of ≥92%, a viscosity of <100 mpa·s, an effective content of ≥99 wt .%, and a water content of <5 wt .%; the nitrogen content is ≥5.5 wt .%; the urea is in powder form passing through a 60-100 mesh sieve, has a nitrogen content of ≥46 wt .%, a biuret content of <0.5 wt .%, and a water content of <0.3 wt .%; the microbial agent is a compound microbial agent composed of Aspergillus penicillioides 、 Aspergillus proliferans and Mortierella alpina 、 Mortierella exigua each 0.1 part, has an effective component of ≥75 wt .%, and an effective viable bacterial count of ≥100 billion / gram.

2. Use according to claim 1, characterized in that, The input amount was 400 kg C / acre.

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