CN113861996A

CN113861996A - Compound soil conditioner for calcareous purple soil and application method thereof

Info

Publication number: CN113861996A
Application number: CN202111230265.7A
Authority: CN
Inventors: 杨占彪; 朱佳敏; 周伦理; 卢晓琳; 徐小逊; 程章; 黄成毅
Original assignee: Chengdu Metropolitan Modern Agricultural Industry Technology Research Institute Co ltd; Sichuan Agricultural University
Current assignee: Chengdu Metropolitan Modern Agricultural Industry Technology Research Institute Co ltd; Sichuan Agricultural University
Priority date: 2021-10-20
Filing date: 2021-10-20
Publication date: 2021-12-31

Abstract

The invention provides a compound soil conditioner for calcareous purple soil and an application method thereof, belonging to the technical field of soil improvement. The composite soil conditioner is prepared by combining sodium carboxymethylcellulose and fly ash according to the weight ratio of 1:10, and the physical and chemical properties of the calcareous purple soil are as follows: total nitrogen 17.36 mg/kg^‑1Total phosphorus 0.45 g.kg^‑118.5 mg/kg of total potassium^‑1Organic matter 9.11 g.kg^‑1The content of water-stable agglomerates was 23.06%, and the pH was 7.79. The compound modifier is specially used for common calcareous purple soil in Sichuan, can greatly improve the water and fertilizer retention performance of the soil, remarkably improve the desertification property of the calcareous purple soil, reduce the volume weight of the soil, increase the porosity and remarkably improve the porosityThe content of aggregates with a grain size of more than 0.3mm in the aggregates with high water stability.

Description

Compound soil conditioner for calcareous purple soil and application method thereof

Technical Field

The invention belongs to the field of soil improvement, relates to the field of soil improvement by using industrial wastes and high molecular compounds, and particularly relates to a compound soil conditioner for calcareous purple soil and an application method thereof.

Background

Due to the continuous increase of population, continuous requesting and destruction of soil resources by human beings, excessive use of agricultural chemicals such as chemical fertilizers and pesticides, soil fertility imbalance, reduction of farmland soil quality, drought water shortage, low water and fertilizer utilization efficiency and surface source pollution, and limitation of high-efficiency and sustainable development of agricultural production in China. The application of the modifying agent is an effective way for controlling water, soil and nutrient loss from the source in modern agriculture.

The fly ash is solid waste residue discharged in the production process of coal-fired enterprises, and improper treatment of the fly ash not only occupies large area of land, but also can cause environmental pollution. At the present stage, the research on the fly ash mainly focuses on the aspects of agriculture, building materials, buildings, chemical industry, environmental protection and the like, and the fly ash serving as a common soil conditioner raw material has the characteristics of light particle weight, porous and loose property, large specific surface area, more active groups and strong adsorption capacity, can promote the agglomeration of soil particles, and the physicochemical property of the fly ash determines that the fly ash can be used as a soil conditioner and a fertilizer filler, so that good conditions are created for the growth and development of crops, and the quality of the crops is improved.

Sodium carboxymethyl cellulose (CMC) is a cellulose ether derivative with a carboxymethyl structure obtained by modifying natural cellulose through an alkalization reaction and an etherification reaction, and as a cellulose derivative, the CMC is very easy to combine with water due to the existence of a hydrophilic group carboxymethyl, and high-molecular polymers are mutually staggered to form a network structure under the action of hydrogen bonds and van der waals force, so that the CMC can be combined with a large amount of water to form hydrogel. The CMC aqueous solution has the characteristics of good thickening, suspension, adhesion, water retention and the like, so the CMC aqueous solution is widely applied to industries such as petroleum, geology, food, textile, printing and dyeing, paper making, ceramics, cosmetics, medicines and the like, and the CMC has rich sources, low cost, easy degradation by microorganisms in soil and no toxicity, so the CMC aqueous solution can be used as a soil conditioner.

The calcareous purple soil is mainly distributed in Sichuan basins and Yunnan mediterra, and the organic matter of the soil is 10 g/kg^-1On the left and right sides, the total nitrogen and total phosphorus content is low, the soil body is shallow, the soil texture is mostly sandy soil, the soil grain pore is large, the ventilation and water permeability is strong, and the capillary action is weak. Because the soil has large particles and small specific surface, the capacities of adsorbing and maintaining nutrients and moisture are poor. In recent years, in the type of farmland, the deterioration is started, the organic matter content of the soil is rapidly reduced, and the aggravation of wind invasion and water invasion forms vicious circle, so that the loss of fertilizers and water is serious, the utilization rate of the fertilizers and water is reduced, the normal growth of plants is not facilitated, and a means capable of being treated is urgently needed.

Currently, researchers have studied the soil improvement effect of the independent application of the CMC and the fly ash, but no research on the application of the CMC and the fly ash to the calcareous purple soil exists at present, and the following problems can be mainly existed from the current research results: (1) because the fly ash hardly contains nitrogen elements and organic matters, the soil nutrition cannot be supplied in a balanced manner by singly applying the fly ash to improve the desertification soil; the coal ash and other solid wastes are used in a combined manner to make up the defect of single application, but the type, proportion and combined use mode of the solid wastes can influence the improvement effect, so how to use the coal ash and other solid wastes in the improvement effect of the calcareous purple soil needs to be further researched; (2) researches on soil nutrient retention and soil stability aggregates by applying CMC as a modifier to soil are rarely mentioned, so that the improvement effect of applying CMC to calcareous purple soil is unknown and specific researches are needed; (3) the physicochemical properties of the soil to be tested are greatly different among different tests, the research results of the fly ash and CMC obtained by the current tests are not universal, and specific analysis is needed for specific problems, so that the research on the improvement of the common calcareous purple soil in Sichuan areas under a compound improved formula is less, a large amount of work still needs to be carried out, and no relevant research can be provided for reference at present.

Therefore, the improvement scheme of the compound modifier for the calcareous purple soil needs to be further researched.

Disclosure of Invention

The invention aims to solve the technical problems and provides a composite soil conditioner for efficiently improving calcareous purple soil and an application method thereof, the composite soil conditioner is specially used for the common calcareous purple soil in Sichuan, and researches show that the composite soil conditioner can greatly improve the water and fertilizer retention performance of the soil, remarkably improve the desertification property of the calcareous purple soil, reduce the volume weight of the soil, increase the porosity and remarkably improve the content of aggregate with the grain size of more than 0.3mm in water stability aggregate.

One purpose of the invention is to provide a compound soil conditioner for calcareous purple soil, which is formed by combining sodium carboxymethylcellulose and fly ash according to the weight ratio of 1:10, wherein the physical and chemical properties of the calcareous purple soil are as follows: total nitrogen 17.36 mg/kg^-1Total phosphorus 0.45 g.kg^-118.5 mg/kg of total potassium^-1Organic matter 9.11 g.kg^-1The content of water-stable agglomerates was 23.06%, and the pH was 7.79.

The composite soil conditioner is obtained by combining sodium carboxymethylcellulose and fly ash according to the weight ratio of 1:10 by a large amount of researches aiming at common calcareous purple soil in Sichuan, and the composite soil conditioner is found to have good water and fertilizer retention performance effects on the calcareous purple soil, well improve the desertification property of the calcareous purple soil, reduce the volume weight of the soil and increase the porosity, and more importantly, the composite soil conditioner can obviously improve the content of water-stable aggregates and improve the content of aggregates with the particle size of more than 0.3mm by 108 percent.

Further, the particle size of the fly ash is 320 meshes, and the water content is 0.5%.

The invention also aims to provide a specific application method of the compound soil conditioner in the aspect of improving the calcareous purple soil, which is to directly apply the compound soil conditioner to the soil or improve the soil by a mode of washing the soil, wherein the application amount of the compound soil conditioner is 30 g/kg/soil.

The invention has the following beneficial effects:

the soil conditioner disclosed by the invention can realize resource utilization of wastes and can solve the problem of stacking of fly ash to a certain extent. Moreover, the composite modifier has obvious improvement effect on the water and fertilizer retention performance of soil, can reduce the volume weight of the soil, increase the porosity and improve the content of aggregates with the grain size of more than 0.3mm in water stability aggregates, can well deal with the problem of soil degradation after excessive soil erosion, and the method is simple.

Drawings

FIG. 1 is a schematic view of a soil column used in an embodiment of the present invention;

FIG. 2 shows the average weight diameter (a) and the geometric average diameter (b) of differently treated agglomerates;

FIG. 3 is a graph of unstable aggregate index (a) and fractal dimension (b) for different treatments of soil aggregates;

FIG. 4 shows the total nitrogen leaching loss variation of different treatments, wherein different letters represent that the significant difference P is less than 0.05 between different treatments on the same days, as follows;

FIG. 5 shows the total phosphorus leaching change for different treatments;

FIG. 6 shows the variation of total potassium leaching in different treatments;

FIG. 7 shows the volume change of different treatment showers;

FIG. 8 shows the pH change of different treatment showers.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following embodiments, and it should be noted that the following embodiments are only for explaining and illustrating the present invention and are not intended to limit the present invention. The invention is not limited to the embodiments described above, but rather, may be modified within the scope of the invention.

Example 1

1. Materials and methods

1.1 Experimental materials

Firstly, a plastic barrel: the diameter is 200mm, the height is 200mm, and the number of the grooves is 27.

② earth pillar leaching test device: a PVC cylindrical tube (see figure 1) with a diameter of 5cm and a height of 30cm, and a water outlet arranged at the bottom of the PVC cylindrical tube and used for collecting the leaching solution, wherein the number of the PVC cylindrical tube is 27.

(iii) test soil

The soil to be tested is lime purple soil collected in 10 months in 2020, and the place is forest park in Longquan mountain city of Longquan district of Chengdu city (the average temperature in the field is 16.5 ℃, the average relative humidity in the year is 81%, and the average annual precipitation is 895.2 mm). And (3) collecting 0-20cm of surface soil by using a soil auger according to a five-point sampling method during soil collection, and taking the surface soil back to a laboratory for air drying. And (2) uniformly mixing the air-dried soil, taking a part of soil by a quartering method, manually removing dry branches and fallen leaves, grinding by using a mortar, and sieving by using a 100-mesh sieve for measuring the basic physicochemical properties of the soil, wherein the results are shown in table 1. The physicochemical properties of the soil to be tested can be seen as follows: total nitrogen 17.36 mg/kg^-1Total phosphorus 0.45 g.kg^-118.5 mg/kg of total potassium^-1Organic matter 9.11 g.kg^-1The content of water-stable agglomerates was 23.06%, and the pH was 7.79.

TABLE 1 physicochemical Properties of the soil tested

Sodium carboxymethylcellulose and fly ash to be tested

The test Fly Ash (FA) is cement-colored powder, the particle size is about 320 meshes, and the water content is 0.5%. The sodium carboxymethylcellulose (CMC) to be tested is purchased from biological engineering and is chemically and analytically pure.

The tested fertilizers were 3 kinds in total, and the details are shown in table 2.

TABLE 2 Fertilizer tested

1.2 pharmaceutical instruments

Experimental drugs:

unless otherwise indicated, the following reagents were all analytical grade.

Sodium hydroxide, hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, methyl red, bromocresol green, absolute ethyl alcohol, potassium permanganate, sodium carbonate, potassium persulfate, 2, 6-dinitrophenol, sodium potassium tartrate, lanthanum chloride, copper sulfate, potassium sulfate, L (+) -ascorbic acid (guaranteed purity), ammonium molybdate, ammonium dihydrogen phosphate, potassium chloride, ammonium chloride, anhydrous ammonia and potassium nitrate.

Test apparatus equipment:

an electric furnace capable of adjusting temperature, an automatic Kjeldahl apparatus, a balance, an acidimeter, a nickel crucible, a muffle furnace, a spectrophotometer, a flame photometer, an autoclave and other common glass instruments.

1.3 test method design

(1) Test treatment

Weighing 1kg of air-dried calcareous purple soil into a plastic barrel (the diameter is 200mm, the height is 200mm), adding a certain amount of Fly Ash (FA) and sodium carboxymethylcellulose (CMC), pouring a small amount of distilled water, uniformly mixing, standing for 7 days, pouring out the mixed soil after standing, air-drying for 15 days, and removing impurities for later use. The experiment was set up with 9 treatments: no soil Conditioner (CK), 1% FA, 3% FA, 0.1% CMC, 0.2% CMC, 1% FA + 0.1% CMC, 1% FA + 0.2% CMC, 3% FA + 0.1% CMC, 3% FA + 0.2% CMC. Each treatment is repeated for 3 times, and a soil column leaching test is carried out, wherein the treatment method comprises the following steps:

TABLE 3 test treatment methods

(2) Soil water stability aggregate test

The soil water-stable aggregate content was determined by wet sieving: weighing 50g of air-dried soil sample in a beaker, adding 100mL of distilled water in the beaker, soaking for 30min, pouring into a 5mm sieve, simultaneously placing 4 sieves of 2mm, 1mm, 0.45mm and 0.25mm, connecting the nested sieves tightly, covering a cover, slowly placing the nested sieves in a plastic barrel, filling the barrel with about 2/3 of distilled water, soaking for 5min, oscillating up and down, wherein the oscillation time exceeds 5min, fishing out after completion, washing the soil sample in each sieve into a tin foil paper box with known weight, drying in an oven at 105 ℃ to constant weight, cooling and weighing to obtain the content of soil aggregates with the particle size of more than 0.25mm and the composition of each particle size. The mass percent water stable agglomerates, Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), unstable agglomerate index and fractal dimension (D) were calculated for each treatment group.

(3) Soil column leaching test

The soil column leaching test device is designed into a PVC circular tube with an upper opening, a closed bottom, a diameter of 5cm and a height of 30cm, and the bottom of the PVC circular tube is used as a water outlet through punching and used for collecting leaching solution (as shown in figure 1). Laying a layer of filter cloth on the surface of the water outlet hole, laying a layer of quartz sand on the filter cloth to play a role in filtering drenching solution, filling 500g of treated air-dried soil into each column, and filling the three fertilizers of ammonium chloride, ammonium dihydrogen phosphate and potassium chloride in the table 2 with the weight of 600 mg.kg^-1The application amount of the fertilizer is mixed and applied to soil, and a quartz sand layer with the thickness of 2-3cm is added on the surface of the soil to cover the soil. The experiment was followed by 9 treatments as described above, each treatment being set to 3 replicates. When the soil column is installed, the added soil is compacted as much as possible and is tightly attached to the wall of the soil column, so that the soil is prevented from generating a cavity or water flows directly along the wall of the soil column when water is added, and a funnel is placed at the lowest part of the soil column and connected with a 250mL conical flask for receiving leaching solution. Adding 250mL of distilled water before leaching experiment to make soil water close to saturation, culturing for three days, performing first soil column leaching, namely slowly pouring 100mL of distilled water, collecting leaching solution within 24h, adding 100mL of distilled water for second leaching at four days intervals, wherein the operation steps are the same for each time, and leaching togetherAnd dissolving the soil column five times, namely leaching the soil column at 1 st, 5 th, 9 th, 13 th d and 17 th d respectively. After each collection of the leaching solution, the volume, pH, total nitrogen and total phosphorus content of the leaching solution were measured. The volume of the leaching solution is directly measured by a measuring cylinder, the pH value is measured by a pH meter, the total nitrogen content of the soil column leaching solution is measured by potassium persulfate oxidation-ultraviolet spectrophotometry, the total phosphorus content is measured by potassium persulfate oxidation-molybdenum antimony anti-spectrophotometry, and the total potassium content is measured by flame photometry.

1.4 data processing and statistics

Excel-2016 is used for data organization, Origin-8.5 is used for mapping, SPSS-27.0 is used for single-factor analysis of variance, correlation analysis and main component analysis of test data, and the level of significance of difference (P <0.05) is tested by Duncan method.

2. Results and discussion (one) Effect of FA and CMC application on Water-stable agglomerates

2.1 Effect of different treatments on soil Water-Stable aggregate composition

After the improver is applied, the content of aggregates with the grain size of more than 0.3mm in soil is mainly obviously influenced, and simultaneously the content of aggregates with the grain size of less than 1mm can be reduced and the content of aggregates with the grain size of more than or equal to 1mm can be increased, wherein the content of the aggregates with the grain size of 2-1mm in a treatment group applied with 0.1% of CMC is obviously increased by 91% compared with CK, while the content of the aggregates with the grain size of 1-0.45mm in a treatment group applied with 1% of FA and 0.1% of CMC in a composite manner is obviously reduced by 82% compared with CK, and the content of the aggregates with the grain size of 0.45-0.3mm is obviously reduced by 77% compared with CK (Table 4). Compared with single application, the FA and CMC compound application has more obvious effect of improving the content of the aggregates with the grain size of more than 0.3mm, wherein the improving range of the treatment group with 1 percent of FA and 0.1 percent of CMC compound application to the content of the aggregates with the grain size of more than 0.3mm is the largest, and reaches 108 percent. At the same FA application level, the content of aggregates in the soil increases in size fraction > 0.3mm with increasing CMC dosage. Under the same CMC application amount, with the increase of the FA application amount, the content of the aggregates with the grain size of more than 0.3mm in the soil has the trend of increasing and then reducing, but the content is still more than CK after reducing.

TABLE 4 Effect of different treatments on soil Water-stable aggregate composition

Note: different letters represent that the obvious difference P between different treatments of the same index is less than 0.05, and the following is the same.

2.2 Effect of different treatments on the mean weight and geometric mean diameter of soil agglomerates

The average weight diameter (MWD) and the Geometric Mean Diameter (GMD) of the aggregates are indexes reflecting the distribution condition of the soil aggregates, and the larger the value is, the larger the soil aggregation effect is, the stronger the stability of the aggregates is, and the higher the corrosion resistance is. The results show that the application of the improver significantly improved the MWD and GMD of soil water-stable agglomerates compared to CK, with a significant 117% improvement in the MWD of the treatment co-applied with 3% FA and 0.2% CMC and a significant 112% improvement in the GMD co-applied with 1% FA and 0.1% CMC. The effect of the compound administration of FA and CMC on the improvement of MWD and GMD is more obvious than that of the single administration, and at the administration level of FA of 0% and 3%, the MWD and GMD are obviously increased along with the increase of the CMC administration amount. When FA was administered alone, both MWD and GMD tended to increase and then decrease as the amount of FA administered increased.

2.3 Effect of different treatments on the unstable pellet index (ELT) and fractal dimension (D) of soil agglomerates

The ELT can directly evaluate the damage degree of the farming measures to the water-stable aggregates and the stability of the structure of the aggregates, and the smaller the value, the more stable the soil structure is. The value D is an index for evaluating the structural characteristics of irregular shapes, and can represent the permeability and the corrosion resistance of the soil aggregate, and the smaller the fractal dimension value is, the higher the permeability and the corrosion resistance of the soil are, and the more stable the aggregate is. The results show that the application of the modifier can reduce both the ELT and the D value compared with CK, wherein the ELT of the treatment which is applied by compounding 1% FA and 0.1% CMC is obviously reduced by 32%, and the D value of the treatment which is applied by 0.2% CMC alone is reduced by 11%; the effect of the composite administration of FA and CMC on the reduction of ELT and D values is more significant than that of the single administration, and the effect of the single administration of CMC on the reduction of ELT and D values is better than that of the single administration of FA, and at the FA administration level of 0% and 3%, the ELT and D values are sequentially reduced along with the increase of the CMC dosage.

(II) Effect of FA and CMC application on soil nutrient

(1) Soil total nitrogen leaching loss characteristic

The change of the TN concentration of the leaching solution in different treatments along with the leaching time is shown in FIG. 4, the TN concentration of the CK leaching solution is in a descending trend along with the change of the leaching time, the change of the TN concentration of the treating group applied with the modifying agent shows that the TN concentration of the CK leaching solution is firstly reduced and then increased and then reduced, the TN concentration of the CK leaching solution is always reduced from the 1 st day to the 9 th day, the concentration of the CK leaching solution is improved at the 13 th day, even the concentration of an individual treating group exceeds the 1 st day, the concentration of the CK leaching solution is reduced to the 17 th day, and the whole solution is in a descending trend. Compared with CK, the TN content of the treating leaching solution compositely applied by 1% of FA and 0.1% of CMC is obviously reduced by 38% compared with CK on day 1, and the TN content of the treating leaching solution compositely applied by 1% of FA and 0.2% of CMC is obviously reduced by 43% compared with CK on day 5. Compared with the single FA or CMC, the composite application has more obvious effect on reducing the total TN leaching loss in the leaching solution within 17 days, and particularly, the reduction range of the total TN leaching loss of the leaching solution is maximum by the composite application of 1 percent of FA and 0.2 percent of CMC, and reaches 40 percent. In the single leaching process, when the CMC is applied independently, the TN content of the leaching solution is sequentially reduced along with the increase of the application amount of the CMC, and the TN content of the leaching solution is gradually reduced and then increased when the FA is applied independently, wherein the TN content of the leaching solution of a 3% FA treatment group is respectively increased by 5% and 1% compared with CK on days 1 and 17.

(2) Soil total phosphorus leaching loss characteristics

The change of TP in the leaching solution under different treatments along with the leaching time is shown in figure 5, the concentration of TP in the CK leaching solution tends to increase first, then decrease and then increase along with the change of the leaching time, and the concentration of TP in the treating group leaching solution applied with the modifying agent gradually increases. In the single leaching process, compared with CK, the application of the modifying agent can reduce the TP content in the leaching solution, the reduction effect of the compound application on the TP of the leaching solution is better than that of the single application, the reduction amplitude of the compound application on the TP of the leaching solution by 3 percent FA and 0.2 percent CMC is the largest on the 1 st day and reaches 39 percent, but the individual group has the phenomenon of increasing, and the treatment group applied by 3 percent FA alone increases by 10 percent compared with CK. When the application amount of FA is 3%, the TP content of the leaching solution is sequentially reduced along with the increase of the CMC application amount, compared with the total TP leaching loss in the leaching solution within 17 days of CK, the total TP leaching loss of a treatment group which is applied by 3% of FA and 0.2% of CMC in a combined way is reduced by 26%, and the total TP leaching loss of a treatment group which is applied by 3% of FA alone is increased by 6% compared with CK.

(3) Soil total potassium leaching loss characteristic

The change of the total potassium content in the eluviation solutions of different treatments along with the leaching times is shown in fig. 6, the total potassium concentration in the eluviation solutions of all the test groups is in a whole descending trend along with the change of the leaching time, wherein the total potassium content in the eluviation solution of CK is in a trend of firstly reducing, then increasing and then reducing, the total potassium content in the eluviation solution of the group to which the modifying agent is applied is gradually reduced, and the concentration of the eluviation solution of the group to which the modifying agent is applied is increased to some extent after the 17 th day. In the single leaching process, compared with CK, the group partially applied with the modifying agent has the effect of reducing the total potassium content in the leaching solution, but also has the phenomenon that the total potassium leaching loss of soil is increased after the modifying agent is applied, and in 1 day, the total potassium content in the leaching solution of the treatment group compositely applied by 1% FA and 0.2% CMC is reduced by 15% compared with CK, but the treatment group applied by 0.1% CMC alone is increased by 31% compared with CK; at the same FA application level, the total potassium content of the leaching solution increased first and then decreased as the CMC application rate increased. Compared with CK, the treatment group applied with 1% FA alone reduces the total leaching loss of the total potassium in the leaching solution within 17 days to the maximum extent, and the reduction extent reaches 16%.

(III) Effect of application of amendment on soil Water Retention and pH

(1) Influence on soil Water Retention

The change of the volume of the leaching solution with different treatments along with the leaching time is shown in fig. 7, the change of the volume of the leaching solution is not obvious as the leaching times are increased, the main change is in a descending trend in the first two leaching volumes, but the change of the leaching volumes after the first two leaching times is not obvious, on the 1 st day, the leaching solution of the treatment group which is applied by compounding 1% of FA and 0.2% of CMC is obviously reduced by 5% compared with CK, and on the 5 th day, the treatment group which is applied by singly applying 3% of FA is obviously reduced by 8% compared with CK. The total amount of water leached from the group to which the modifier was applied was reduced compared to CK, and the total volume of leaching solution in the treatment group, which was applied with 1% FA and 0.1% CMC in combination, was reduced by 3% over the 17 day period compared to CK.

(2) Influence on the pH of the soil drench

The change of the pH of the leaching solution with different treatments along with the leaching time is shown in figure 8, the pH of the leaching solution tends to increase along with the increase of the leaching times, but the overall change is small and mainly ranges from 7.5 to 8.2, and the difference between the maximum value and the minimum value is not more than 0.7. The application of the modifier reduced the pH of the leach solution compared to CK during a single leaching event, but there were individual groups with an overall pH greater than CK, with the leach solution pH significantly reduced by 5% for the treatment group applied with 0.2% CMC alone compared to CK and 2% for the treatment group applied with 3% FA alone compared to CK. At the same FA application level, the pH of the leaching solution gradually decreased with increasing CMC application rate, while at the same CMC application rate, the pH of the leaching solution tended to increase with increasing FA dosing rate.

In conclusion, the following results show that: compared with the single application of FA and CMC, the composite application of the FA and the CMC has partial promotion effect on the formation of soil water-stable aggregates, especially the treatment group of the composite application of 1 percent of FA and 0.1 percent of CMC improves the content of aggregates with the grain size of more than 0.3mm by 108 percent, the overall MWD and GMD levels of the composite application experimental group are higher than those of the single application, and the reduction effect on ELT and D values is more obvious. In the aspect of nutrients, the effect of the compound application on reducing the total leaching loss of the nutrients in the leaching solution within 17 days is more obvious, the total leaching loss of TN (total nutrient solution) of the leaching solution is reduced by 40% by the compound application of 1% FA and 0.2% CMC, and the total leaching loss of TP of a treatment group by the compound application of 3% FA and 0.2% CMC is reduced by 26%, because the formation of a soil structure can be promoted after the two modifying agents are compounded, and the adsorption effect on moisture and nutrients is stronger.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The compound soil conditioner for the calcareous purple soil is characterized by being prepared by combining sodium carboxymethylcellulose and fly ash according to a weight ratio of 1:10, wherein the physical and chemical properties of the calcareous purple soil are as follows: total nitrogen 17.36 mg/kg^-1Total phosphorus 0.45 g.kg^-118.5 mg/kg of total potassium^-1Organic matter 9.11 g.kg^-1The content of water-stable agglomerates was 23.06%, and the pH was 7.79.

2. The composite soil conditioner according to claim 1, wherein the fly ash has a particle size of 320 mesh and a water content of 0.5%.

3. The method for applying the compound soil conditioner for limy purple soil as set forth in claim 1 or 2, wherein the compound soil conditioner is applied directly to soil or is improved by washing the soil, and the amount of the compound soil conditioner applied is 30 g/kg/soil.