Acid soil conditioner, acid farmland soil-crop system improvement method and application of acid farmland soil-crop system improvement method

Abstract

The invention discloses an acid soil conditioner, an acid farmland soil-crop system improvement method and application thereof, and belongs to the technical field of acid soil improvement. The invention provides an acidic soil conditioner. The acidic soil conditioner is prepared from carbon adsorption polyglutamic acid and biochar. The acid soil conditioner can significantly improve the soil quality, can significantly reduce the use amount of biochar and carbon adsorption polyglutamic acid when being used for acid farmland soil improvement, and can synergistically enhance the soil enzyme activity, increase the absorption of nitrogen, phosphorus, calcium and magnesium by root systems, and improve the soil quality. The ear number per mu, the grain number per ear, the thousand seed weight, the grain protein content and the gluten content are improved, and the effect of simultaneously improving the yield and the quality of the wheat is achieved. According to the method, an efficient acid farmland crop production improvement technology is established, and technical support and theoretical reference are provided for acid farmland improvement and guarantee of grain safety production.

Description

Technical Field

[0001] The invention belongs to the technical field of acidic soil improvement, and in particular relates to an acidic soil conditioner, an acidic farmland soil-crop system improvement method and applications thereof. Background Art

[0002] Soil acidification can lead to soil structure degradation, soil potassium, sodium, calcium, magnesium and other nutrient deficiencies, reduced soil enzyme activity, affecting soil nutrient supply and crop growth and development, and reducing crop yield and quality. Therefore, establishing effective acid soil improvement measures and preventing and controlling soil acidification are important ways to improve soil quality and farmland ecological environment. Traditional lime improvement is simple to operate and has a quick effect on soil acidification, but it can easily lead to soil compaction and re-acidification, aggravating the degree of acidification. Biochar is favored by soil scholars because of its porous and large surface area, which can adsorb and fix the main nutrients in the soil and reduce nutrient loss. However, according to past experience, low amounts of biochar have no significant effect on improving the pH of acidic soils. Although the improvement effect can be improved after the application amount is increased, excessive application may inhibit the normal growth and development of crops because biochar itself contains high concentrations of carbon and nitrogen elements. In addition, heavy metals and other pollutants that may be contained in it will enter the natural environment during the use of biochar, causing harm to soil and aquatic ecosystems. Therefore, it is particularly important to provide a soil conditioner and improvement method that can effectively improve soil quality, increase crop quality and yield, and reduce the use of conditioners. Summary of the invention

[0003] In view of this, the object of the present invention is to provide an acidic soil conditioner that can effectively improve the quality of acidic soil and increase crop yield and quality while reducing the amount of application.

[0004] Another object of the present invention is to provide an application of the acidic soil conditioner in improving acidic soil.

[0005] Another object of the present invention is to provide a method for improving acidic farmland soil-crop system.

[0006] Another object of the present invention is to provide an application of the acidic soil conditioner or the acidic farmland soil-crop system improvement method in improving crop yield and quality.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The invention provides an acidic soil conditioner, which comprises the following raw materials: charcoal-adsorbed polyglutamic acid and biochar; the mass ratio of the charcoal-adsorbed polyglutamic acid to the biochar is 1:200-800.

[0009] Preferably, the pH of the carbon adsorbed polyglutamic acid is 4-5.

[0010] Preferably, the biochar comprises straw biochar.

[0011] The invention also provides an application of the acidic soil conditioner in improving acidic soil.

[0012] Preferably, the acidic soil includes yellow-brown soil, sand ginger black soil, brick red soil, red soil, red soil or yellow soil.

[0013] The present invention also provides a method for improving an acidic farmland soil-crop system, comprising applying the acidic soil conditioner to the acidic farmland soil.

[0014] Preferably, the biochar in the acidic soil conditioner is applied before the soil is rotary tilled and then rotary tilled into the soil.

[0015] Preferably, the carbon-adsorbed polyglutamic acid in the acidic soil conditioner is dissolved in water and sprayed.

[0016] Preferably, the application amount of the acidic soil conditioner is 700-1300 kg / mu.

[0017] The present invention also provides an application of the acidic soil conditioner or the acidic farmland soil-crop system improvement method in improving soil quality and / or improving crop quality and yield.

[0018] Beneficial effects of the present invention:

[0019] The present invention provides an acidic soil conditioner, which is composed of carbon-absorbed polyglutamic acid and biochar. The application of biochar can enhance the water repellency of the soil, deteriorate the water holding capacity, increase the soil runoff, and make the soil nitrogen more easily lost. Adding polyglutamic acid gel material helps to alleviate the problem of increased soil runoff due to the application of biochar to the greatest extent. The present invention compounds carbon-absorbed polyglutamic acid and biochar to obtain an acidic soil conditioner that can improve soil structure, increase soil salinity, alleviate soil acidification, and increase soil enzyme activity and nutrient effectiveness, thereby improving soil quality.

[0020] The acidic soil conditioner of the present invention is used for improving acidic farmland soil. By reducing the amount of biochar and charcoal-absorbed polyglutamic acid, the soil enzyme activity can be synergistically enhanced, the root nitrogen, phosphorus, calcium and magnesium absorption can be increased, the number of ears per mu, the number of grains per ear, and the thousand-grain weight can be increased, and the wheat yield can be increased by 26%, the crude protein of wheat grains can be increased by 77%, and the gluten content of wheat can be significantly increased, thereby achieving the effect of simultaneously improving the yield and quality of wheat. The present invention can significantly reduce the amount of biochar and charcoal-absorbed polyglutamic acid by reducing the amount of biochar and charcoal-absorbed polyglutamic acid, and the amount can be reduced by more than half compared with the amount of the two when applied alone. The improvement effect of acidic farmland soil can reach or even exceed the level of single application, while reducing production costs and improving crop quality and yield. The present invention establishes an efficient application technology for improving acidic farmland production, providing technical support and theoretical reference for improving acidic farmland and ensuring food safety production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the technical route of Test Example 1 and Test Example 2;

[0022] Figure 2 The nutrient content of plants under different treatments in Experiment 2; the data are mean ± standard error, different letters indicate significant differences among treatments (P<0.05), CK: control, C: biochar, E: charcoal-adsorbed polyglutamic acid, CE: biochar and charcoal-adsorbed polyglutamic acid combined with reduced application;

[0023] Figure 3 This is the correlation between wheat yield and quality and soil indicators in Experimental Example 2. DETAILED DESCRIPTION

[0024] The present invention provides an acidic soil conditioner, which comprises the following raw materials: charcoal-adsorbed polyglutamic acid and biochar; the mass ratio of the charcoal-adsorbed polyglutamic acid to the biochar is preferably 1:200-800.

[0025] In the present invention, the carbon-adsorbed polyglutamic acid is a new type of material obtained by treating biochar on the basis of polyglutamic acid, which can be purchased through conventional channels or prepared by conventional methods. There is no special limitation on the source of the carbon-adsorbed polyglutamic acid. As an optional embodiment, the carbon-adsorbed polyglutamic acid can be purchased through Henan Naian Biotechnology Co., Ltd.; preferably, the carbon-adsorbed polyglutamic acid has a carbon-adsorbed polyglutamic acid content of ≥10g / kg and an organic matter content of ≥80g / kg. In the present invention, the pH of the carbon-adsorbed polyglutamic acid is preferably 4 to 5, more preferably 4.3 or 4.1 to 4.3 or 4.3 to 4.5.

[0026] In the present invention, there is no particular limitation on the type of biochar, and preferably includes straw biochar; the type of straw can be obtained locally according to actual needs or local crop planting conditions, and is preferably any one or more of common crop straws such as corn straw, wheat straw, cotton straw or soybean straw, and more preferably wheat straw or corn straw. The present invention does not particularly limit the preparation method of the biochar, and it can be conventionally selected according to actual needs; as an optional embodiment, the preparation conditions of the biochar preferably include: a pyrolysis temperature of 450°C to 650°C, and a carbonization time of 4 to 6 hours. In the present invention, in some embodiments, the fixed carbon content in the biochar is preferably 300-1000 g / kg, more preferably 650 g / kg or 500-650 g / kg or 650-800 g / kg; the total nitrogen content in the biochar is preferably 2-8 g / kg, more preferably 4.34 g / kg or 3-4.34 g / kg or 4.34-6 g / kg; the available phosphorus content in the biochar is preferably 5-15 g / kg, more preferably 10.2 g / kg or 7.5-10.2 g / kg or 10.2-12.5 g / kg; the available potassium content in the biochar is preferably 40-80 g / kg, more preferably 55.65 g / kg or 50-55.65 g / kg or 55.65-70 g / kg. In other embodiments, the total carbon content in the biochar is preferably 300-1000 g / kg, more preferably 507 g / kg, 400-507 g / kg, or 507-650 g / kg; the total nitrogen content in the biochar is preferably 2-8 g / kg, more preferably 2.10 g / kg, 1.5-2.10 g / kg, or 2.10-4.5 g / kg; the total phosphorus content in the biochar is preferably 5-15 g / kg, more preferably 8.37 g / kg, 7.5-8.37 g / kg, or 8.37-10 g / kg; the total potassium content in the biochar is preferably 5-15 g / kg, more preferably 9.33 g / kg, 7-9.33 g / kg, or 9.33-12 g / kg. In the present invention, the pH of the biochar is preferably 9-11, more preferably 10.2, 9.65-10.2, or 10.2-10.5.

[0027] In the present invention, the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is preferably 1:200-800, more preferably 1:461 or 1:290-461 or 1:400-500 or 1:461-600.

[0028] The invention also provides an application of the acidic soil conditioner in improving acidic soil.

[0029] In the present invention, there is no particular limitation on the type of the acidic soil, preferably including yellow-brown soil, sandy ginger black soil, brick red soil, red soil, red soil or yellow soil, more preferably yellow-brown soil. In the present invention, the geographical range of the acidic soil conditioner can be selected according to actual needs or the conventional distribution range of acidic soil, preferably including Henan, Anhui, Shaanxi, Hubei, Jiangsu, Sichuan or Jiangxi, more preferably Henan, and more preferably southern Henan.

[0030] The present invention also provides a method for improving an acidic farmland soil-crop system, preferably comprising applying the acidic soil conditioner to the acidic farmland soil.

[0031] In the present invention, the application method of the biochar and carbon-absorbed polyglutamic acid in the acidic soil conditioner can be conventionally selected according to actual needs. As an optional embodiment, the biochar is preferably applied before the soil is rotary tilled and then rotary tilled into the soil; the carbon-absorbed polyglutamic acid is dissolved in water and sprayed, and the amount of water can be conventionally selected according to actual needs. As an optional embodiment, the mass volume ratio of the carbon-absorbed polyglutamic acid to water is preferably 1kg: 100-500L, more preferably 1kg: 340-350L or 1kg: 103-345L or 1kg: 345-400L; the carbon-absorbed polyglutamic acid is preferably applied in batches, and the number of applications is preferably 2-3 times; the application period can be conventionally selected according to the crop type and growth conditions. For example, when the crop planted in the acidic farmland soil is wheat, the carbon-absorbed polyglutamic acid is preferably applied twice before sowing and in the seedling stage, or twice in the seedling stage and the greening stage. In the present invention, the types of crops planted in the acidic farmland soil can be conventionally selected according to actual needs, for example, including but not limited to wheat, corn, cotton, soybean, sorghum, etc.

[0032] In the present invention, the application amount of the acidic soil conditioner is preferably 700-1300 kg / mu, more preferably 935.405 kg / mu or 850-935.405 kg / mu or 935.405-1100 kg / mu.

[0033] The present invention also provides an application of the acidic soil conditioner or the acidic farmland soil-crop system improvement method in improving soil quality and / or improving crop quality and yield.

[0034] Through in-situ acidic farmland soil cultivation test, the acidic soil conditioner of the present invention can significantly increase soil pH, electrical conductivity, available potassium, microaggregate ratio, and soil sucrase and urease activities, and the soil comprehensive quality SQI index is improved by 46%. It shows that the acidic soil conditioner of the present invention can improve soil structure, increase soil salt content, alleviate soil acidification, increase soil enzyme activity and nutrient effectiveness, and thus improve soil quality. Through field verification in acidic farmland, biochar mainly reduces the content of exchange acid, increases organic matter and base saturation, alleviates soil acidification, and can significantly increase the activity of urease and cellulase, increase root nitrogen absorption, ear number per mu, ear number and grain protein content, and achieve wheat yield and quality improvement; carbon adsorption of polyglutamic acid significantly increases soil phosphatase activity and root phosphorus, calcium and magnesium absorption, increases gluten content, and thus improves wheat quality. The acidic soil conditioner of the present invention can synergistically enhance soil enzyme activity, increase root nitrogen, phosphorus, calcium and magnesium absorption, increase the number of ears per mu, the number of grains per ear, and the thousand-grain weight, and can increase wheat yield by 26%, wheat grain crude protein by 77%, and significantly increase wheat gluten content, thereby achieving the effect of simultaneously improving wheat yield and quality. In addition, the present invention can significantly reduce the amount of biochar and charcoal-absorbed polyglutamic acid by reducing the amount of biochar and charcoal-absorbed polyglutamic acid, and the amount can be reduced by more than half compared with the amount of the two when applied alone, and the improvement effect on acidic farmland soil can reach or even exceed the level of single application.

[0035] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0036] In the following embodiments, unless otherwise specified, all of them are conventional methods.

[0037] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0038] Example 1

[0039] An acidic soil conditioner, the acidic soil conditioner is composed of the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:461;

[0040] The biochar is wheat straw biochar; the pH of the biochar is 10.2; and the pH of the charcoal adsorbing polyglutamic acid is 4.3.

[0041] Example 2

[0042] An acidic soil conditioner, the acidic soil conditioner is composed of the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:290;

[0043] The biochar is corn straw biochar; the pH of the biochar is 9.65; and the pH of polyglutamic acid adsorbed on the biochar is 4.3.

[0044] Example 3

[0045] An acidic soil conditioner, the acidic soil conditioner is composed of the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:600;

[0046] The biochar is cotton straw biochar; the pH of the biochar is 9; and the pH of the charcoal adsorbing polyglutamic acid is 4.

[0047] Example 4

[0048] An acidic soil conditioner, the acidic soil conditioner is composed of the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:400;

[0049] The biochar is wheat straw biochar; the pH of the biochar is 10.5; and the pH of the charcoal adsorbing polyglutamic acid is 4.5.

[0050] Example 5

[0051] An acidic soil conditioner, the acidic soil conditioner is composed of the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:500;

[0052] The biochar is soybean straw biochar; the pH of the biochar is 9.5; and the pH of polyglutamic acid adsorbed on the biochar is 4.1.

[0053] Example 6

[0054] A method for improving acidic farmland soil, comprising applying the acidic soil conditioner of Example 1 to acidic farmland soil; and planting wheat in the acidic farmland soil;

[0055] The biochar in the acidic soil conditioner is applied before soil tillage and then tilled into the soil; the charcoal-adsorbed polyglutamic acid is dissolved in water and sprayed, and is applied twice before wheat sowing and in the seedling stage respectively; the application amount of the acidic soil conditioner is 935.405 kg / mu, of which the application amount of biochar is 933.380 kg / mu and the application amount of charcoal-adsorbed polyglutamic acid is 2.025 kg / mu.

[0056] Example 7

[0057] A method for improving acidic farmland soil, comprising applying the acidic soil conditioner of Example 2 to acidic farmland soil; and planting wheat in the acidic farmland soil;

[0058] The biochar in the acidic soil conditioner is applied before soil tillage and then tilled into the soil; the charcoal-adsorbed polyglutamic acid is dissolved in water and sprayed, and is applied three times before wheat sowing, in the seedling stage and in the greening stage; the application amount of the acidic soil conditioner is 700 kg / mu, of which the application amount of biochar is 697.595 kg / mu and the application amount of charcoal-adsorbed polyglutamic acid is 2.405 kg / mu.

[0059] Example 8

[0060] A method for improving acidic farmland soil, comprising applying the acidic soil conditioner of Example 3 to acidic farmland soil; and planting corn in the acidic farmland soil;

[0061] The biochar in the acidic soil conditioner is applied before soil tillage and then tilled into the soil; the charcoal-adsorbed polyglutamic acid is dissolved in water and sprayed, and is applied twice before corn sowing and at the seedling stage respectively; the application amount of the acidic soil conditioner is 1300kg / mu, of which the application amount of biochar is 1297.837kg / mu and the application amount of charcoal-adsorbed polyglutamic acid is 2.163kg / mu.

[0062] Example 9

[0063] A method for improving acidic farmland soil, comprising applying the acidic soil conditioner of Example 4 to acidic farmland soil; soybeans are planted in the acidic farmland soil;

[0064] The biochar in the acidic soil conditioner is applied before soil tillage and then tilled into the soil; the charcoal-adsorbed polyglutamic acid is dissolved in water and sprayed, and is applied twice at the initial flowering stage and the peak flowering stage of soybeans respectively; the application amount of the acidic soil conditioner is 850kg / mu, of which the application amount of biochar is 847.880kg / mu and the application amount of charcoal-adsorbed polyglutamic acid is 2.120kg / mu.

[0065] Example 10

[0066] A method for improving acidic farmland soil, comprising applying the acidic soil conditioner of Example 5 to acidic farmland soil; cotton is planted in the acidic farmland soil;

[0067] The biochar in the acidic soil conditioner is applied before soil tillage and then incorporated into the soil after tillage; the charcoal-adsorbed polyglutamic acid is dissolved in water and sprayed, and is applied twice at the initial flowering stage and the peak flowering stage of cotton respectively; the application amount of the acidic soil conditioner is 1100kg / mu, of which the application amount of biochar is 1097.804kg / mu and the application amount of charcoal-adsorbed polyglutamic acid is 2.196kg / mu.

[0068] Experimental Example 1 Effects of different material combinations on the improvement of acidic farmland soil in southern Henan

[0069] 1. Test materials

[0070] The test soil was collected in Xiping County, Zhumadian City, Henan Province (33°10′N, 113°36′E). The area is located in the transition zone from the northern subtropical zone to the warm temperate zone. The climate belongs to the subhumid continental monsoon climate, with an average annual temperature of 14.8℃ and a rainfall of 852mm. The local planting method is a typical winter wheat / summer corn rotation system. The test soil type is yellow-brown soil, with a clay content of 35%, a soil pH of 4.8, organic matter of 46.6g / kg, total nitrogen of 4.2g / kg, available phosphorus of 31.51mg / kg, and available potassium of 112.32mg / kg.

[0071] The test lime was 99% slaked lime; the carbon-adsorbed polyglutamic acid was provided by Henan Naian Biotechnology Co., Ltd., with a carbon-adsorbed polyglutamic acid content ≥10g / kg, organic matter ≥80g / kg, and pH 4.3; the biochar was wheat straw charcoal, with a pyrolysis temperature of 550℃~600℃, a carbonization time of 4~6h, a pH of 10.2, fixed carbon of 650g / kg, total nitrogen of 4.34g / kg, available phosphorus of 10.2g / kg, and available potassium of 55.65g / kg.

[0072] 2. Soil cultivation test design

[0073] According to previous experience, low amounts of biochar have little effect on improving the pH of acidic soils, and an application rate greater than 1% or even 5% can significantly increase soil pH. In situ acidic farmland soil (pH 4.8) was used for soil cultivation experiments, and lime, biochar, and carbon-adsorbed polyglutamic acid were applied alone and in random combination with reduced application, with four replicates for each treatment:

[0074] The soil without amended materials was set as the control (CK);

[0075] Treatment A: 1.6% lime added by soil weight;

[0076] Treatment C: 8.9% biochar added by soil weight;

[0077] Treatment E: adding soil weight carbon to adsorb polyglutamic acid 0.6‰;

[0078] Treatment AC: 0.16% lime + 8.01% biochar addition;

[0079] Treatment AE: adding 0.16% lime + 0.54‰ carbon to adsorb polyglutamic acid;

[0080] Treatment CE: adding 5.93% biochar + 0.2‰ charcoal to adsorb polyglutamic acid;

[0081] Treatment ACE: Add 0.16% lime + 4.45% biochar + 0.23‰ charcoal to adsorb polyglutamic acid.

[0082] The pots were filled on April 3, 2022, with 600 g of air-dried soil (passed through a 2 mm sieve) in each pot. The culture temperature was 17-31 ° C, and water was added by weighing to maintain the soil water content at 60% of the maximum field water holding capacity. The culture was carried out for 60 days. After the soil culture was completed, it was passed through a 2 mm sieve and air-dried for the determination of pH, conductivity, soil aggregates, soil nutrients and enzyme activity.

[0083] 3. Index determination

[0084] Soil pH and conductivity were determined using a water-soil ratio of 1:5; soil organic matter was determined using the potassium dichromate volumetric method-external heating method; soil total nitrogen was determined using the semi-micro Kjeldahl method; available potassium was determined using NH4OAc extraction and flame photometry; available phosphorus was determined using the Osson method (0.5 mol / L NaHCO3 extraction-molybdenum antimony colorimetric method); soil urease, alkaline phosphatase and sucrase activities were determined using enzyme-linked immunosorbent assay kits (Huabo Deyi Biotechnology Co., Ltd., Beijing), and absorbance was measured using a multifunctional microplate reader (BioTek Synergy2 Gene 5, USA) at a wavelength of 450 nm. Soil aggregates were determined using the dry sieving method: air-dried soil samples were thoroughly mixed, and sieved from bottom to top with 0.053, 0.25 and 2 mm, respectively. 50 g of soil sample was weighed and placed in the top sieve, with an amplitude of 10 cm, 30 times / min, and sieved manually for 2 min. Soil samples from each sieve and the bottom plate were collected and weighed and recorded. The soil weight percentage of each sieve is used to describe the distribution of soil aggregates (super-large aggregates > 2 mm, large aggregates 0.25-2 mm, micro-aggregates 0.053-0.25 mm, clay particles < 0.053 mm). The mean weight diameter (MWD) of the soil is calculated as follows: (1) Calculate the product of the weight percentage of each aggregate and the mean diameter of that grade; (2) The sum of the above products of all measured aggregate particle sizes is the mean weight diameter.

[0085] 4. Data processing

[0086] SPSS26.0 was used for one-way analysis of variance, principal component analysis, and common factor analysis of variance. The LSD method was used in the analysis of variance to test the significance of differences between treatments.

[0087] 5. Soil quality evaluation method

[0088] (1) Calculation of the membership degree of each indicator

[0089] Soil quality is evaluated by calculating the membership of soil indicators, and the indicators are converted into dimensionless values ​​of 0 to 1, so as to achieve the quantification of indicators. A neutral or slightly acidic soil pH is beneficial to crop growth, and a peak-type membership function is used; the more soil organic matter, total nitrogen, available phosphorus, and available potassium are within a certain range, the better the soil quality is, and a Rongshang-type membership function is used; the membership of soil conductivity, aggregates, and soil enzyme activity is the ratio of the measured value to the maximum value.

[0090] (2) Comprehensive evaluation of soil quality

[0091] Based on previous research, the indicators that can affect soil functions and are sensitive to soil environmental changes are used as soil quality evaluation indicators. Principal component analysis (PCA) can reduce multiple indicators to a few comprehensive indicators, making the variables independent of each other. The indicators with a load greater than 0.7 in each principal component are combined with correlation analysis to be compiled into the minimum data set (MDS). The MDS is subjected to factor analysis, and the proportion of the common factor variance of each indicator to the total common factor variance is used as the indicator weight for soil quality evaluation. According to the addition and multiplication method of fuzzy mathematics, the weight value and membership value of each indicator are weighted and summed to calculate the soil quality index (SQI). The larger the SQI value, the better the soil quality.

[0092] 6. Results Analysis

[0093] (1) Effects of different improved materials on soil pH and conductivity

[0094] Too low soil pH will lead to soil nutrient imbalance and soil fertility decline. As shown in Table 1, except for treatment E, the single application and mixed application of each improved material significantly increased soil pH, with an increase of 27% to 68% (P<0.05). Among them, the soil pH of treatments A, C, AC, CE, and ACE increased to above 6.5, indicating that the single application of lime and biochar and the combined application of biochar and charcoal-adsorbed polyglutamic acid can effectively alleviate soil acidification.

[0095] Soil electrical conductivity is used to characterize the total water-soluble salt ion content of the soil. As shown in Table 1, compared with CK, soil electrical conductivity in treatments C, AC, CE, and ACE increased significantly (P<0.05), ranging from 11.44 to 19.83 times. Therefore, biochar alone and its reduced application with lime, or charcoal adsorbed polyglutamic acid can significantly increase soil salt ion content and improve soil acid buffering capacity.

[0096] Table 1 Changes in soil pH and conductivity after application of different improved materials

[0097] deal with Soil pH Conductivity (μS / cm) CK 4.73±0.01f 71.33±3.97e A 7.95±0.01a 136.63±21.75de C 7.31±0.06cd 1486.00±118.22a E 4.73±0.05f 74.4±9.01e AC 7.40±0.08b 1166.33±40.67b AE 6.01±0.04e 118.83±3.84de CE 7.39±0.02b 1156.33±49.66b ACE 7.26±0.01d 887.33±70.61c

[0098] Note: Data are mean ± standard error, different letters indicate significant differences among treatments (P<0.05). A: lime C: biochar E: charcoal adsorbed polyglutamic acid. Same below.

[0099] (2) Effects of combined application of different improved materials on soil nutrients

[0100] Organic matter participates in the formation of soil structure and nutrient decomposition, which helps to improve soil fertility and acid-base buffering. The results are shown in Table 2. The organic matter content of all treatments decreased to varying degrees. This may be due to the short-term cultivation experiment, in which the improved materials accelerated the decomposition of soluble organic matter. Compared with CK, the total nitrogen content of the soil in treatments AC and AE increased by 14% and 12%, respectively. Soil available phosphorus refers to the soil phosphorus component that can be absorbed and utilized by plants in the season, including all water-soluble phosphorus, part of adsorbed phosphorus and organic phosphorus. The available phosphorus content can be used to evaluate the soil phosphorus supply level. Compared with CK, the soil available phosphorus content of treatments A and CE increased by 88% and 39%, respectively; the soil available potassium content of treatments C, AC, CE, ACE, etc. increased significantly (P<0.05), with an increase range of 10.87 times to 16.87 times.

[0101] Table 2 Changes in soil nutrients after application of different improved materials

[0102] deal with Organic matter (%) Total nitrogen (%) Available phosphorus (mg / kg) Available potassium (g / kg) CK 5.43±0.04a 0.42±0.03cd 27.35±1.23d 109.44±1.4e A 4.33±0.21d 0.42±0.02cd 51.37±2.31a 82.74±1.83e C 4.96±0.07b 0.39±0.02d 33.24±2.36bcd 1955.75±25.41a E 4.27±0.10d 0.34±0.01e 32.15±1.81cd 98.56±1.67e AC 4.54±0.12cd 0.48±0.03a 34.84±1.24bcd 1827.48±40.38b AE 4.28±0.04d 0.47±0.05a 28.45±1.54c 106.14±3.68e CE 4.66±0.13c 0.42±0.03cd 37.99±4bc 1549.01±47.38c ACE 4.65±0.11c 0.44±0.02bc 34.43±0.34cd 1298.75±23.14d

[0103] (3) Effects of combined application of different improved materials on soil enzyme activity

[0104] Soil sucrase, urease and phosphatase are important enzymes for the transformation of carbon, nitrogen and phosphorus in soil, respectively, and affect the soil carbon decomposition and the supply capacity of nitrogen and phosphorus nutrients. The activities of enzymes such as sucrase, urease and alkaline phosphatase in acidic soil generally show the rule of acidification inhibition and alkalinization activation. As shown in Table 3, the soil sucrase activity of treatments C, AC, AE, CE and ACE increased significantly (P<0.05), with an increase range of 12% to 33%. This may be due to the addition of improved materials to increase soil pH, soil microbial quantity and activity, thereby increasing sucrase activity. The change in soil alkaline phosphatase activity in treatment CE was not significant, and the phosphatase activity in other treatments decreased (P<0.05). Generally, the activity of alkaline phosphatase is enhanced in soils with high organic carbon content. The improvement time of this experiment was relatively short and the soil organic matter showed a decreasing trend, which may cause the decrease of soil alkaline phosphatase. The soil urease activity of treatment CE increased significantly, while the urease activity of other treatments decreased significantly (P<0.05). This may be because the activity of soil urease decreases with the increase of total nitrogen and hydrolyzable nitrogen in the soil.

[0105] Table 3 Changes in soil enzyme activity after application of different improved materials

[0106]

[0107]

[0108] (4) Effects of combined application of different improved materials on soil aggregates

[0109] Soil aggregates are the particle units of soil structure, which affect soil quality by regulating soil physicochemical and biological properties. As shown in Table 4, the proportion of large aggregates of 2-0.25 mm in each treatment soil is the largest, followed by super-large aggregates greater than 2 mm and micro-aggregates of 0.25-0.053 mm. As shown in Table 4, compared with CK, the proportion of super-large aggregates in the particle size range greater than 2 mm in treatment AE increased by 73%. Soil microaggregates can reflect the storage and conversion performance, release and supply performance of soil nutrients, and soil buffering performance. Compared with CK, the proportion of microaggregates in treatments A, C, AC, and ACE increased significantly, with an increase of 54% to 83%, indicating that these treatments can improve the storage and release capacity of soil nutrients. The higher the soil MWD value, the better the soil structure and stability. The MWD of treatment AE increased by 36%, and the soil stability was the best.

[0110] Table 4 Changes in soil aggregates after application of different improved materials

[0111] deal with Super large aggregates (%) Large aggregates (%) Microaggregates (%) Sticky powder particles (%) MWD(mm) CK 12.19±3.43bc 72.69±3.85b 13.04±1.43c 0.86±0.47e 0.25±0.03ab A 11.24±1.64c 64.38±0.24ce 20.36±1.35b 3.47±0.50cd 0.26±0.02ab C 10.33±0.64cd 65.87±2.63ce 20.93±0.47b 4.04±0.68bc 0.19±0.04b E 6.91±5.95d 75.95±7.27a 13.96±0.31c 4.66±1.20b 0.18±0.07b AC 8.43±0.41d 60.89±1.34e 23.83±1.02a 7.29±0.42a 0.20±0.01b AE 21.11±1.68a 63.61±2.06ce 10.46±1.53d 3.77±0.31bc 0.34±0.02a CE 16.07±3.40b 67.85±5.07bc 13.39±1.96c 2.61±0.72d 0.25±0.06ab ACE 12.57±1.98bc 66.03±1.49ce 20.13±1.01b 3.57±0.25c 0.24±0.03b

[0112] (5) Soil quality evaluation

[0113] 1) Establishment of soil quality evaluation index system

[0114] The results of principal component analysis are shown in Table 5. There are 4 principal components with characteristic roots greater than 1, and the cumulative contribution rate is greater than 85%, which can reflect the changes of most soil indicators. The loads of soil pH, conductivity, available potassium, sucrase, and macroaggregates in principal component P1 are greater than 0.7, and they are included in the minimum data set; the loads of alkaline phosphatase, super-large aggregates, and MWD in principal component P2 are greater than 0.7. Because super-large aggregates and MWD are extremely significantly correlated (r=0.992**), the indicator MWD with a larger load is included in the minimum data set; organic matter and urease are included in principal component P3; and available phosphorus is included in principal component P4. In summary, there are 10 indicators included in the minimum data set (MDS), namely pH, conductivity, organic matter, available phosphorus, available potassium, urease, alkaline phosphatase, sucrase, macroaggregates, and MWD.

[0115] Table 5 Principal component analysis, common factor variance and weight of each index

[0116]

[0117] 2) Minimum data set indicator membership conversion

[0118] The results of the index membership of the minimum data set of each treatment are shown in Table 6. The membership of available phosphorus, soil urease, alkaline phosphatase, sucrase, macroaggregates, and MWD in the control treatment were all greater than 0.5, indicating that these characteristics were not limiting factors for soil quality, while soil pH, electrical conductivity, organic matter, and available potassium were limiting factors for the control soil quality.

[0119] Table 6 Indicator membership of each processing minimum data set

[0120]

[0121] 3) Soil quality evaluation based on soil comprehensive index method

[0122] The results of SQI scores for all treatments are shown in Table 7. The SQI scores of all treatments are from high to low: CE>C>ACE>AC>AE>A>CK>E. According to the five-level classification method: SQI ≥ 0.8 is good soil quality, 0.6 ≤ SQI < 0.8 is good, 0.4 ≤ SQI < 0.6 is medium, 0.2 ≤ SQI < 0.4 is poor, SQI < 0.2 is poor, and the soil quality of all treatments is above medium. The soil quality of treatments CE, C and ACE increased by 33% to 46% compared with the control.

[0123] Table 7 Soil quality comprehensive index (SQI) of each treatment

[0124]

[0125] The correlation results between the comprehensive soil quality index and various indicators are shown in Table 8. The comprehensive soil quality index was significantly positively correlated with soil pH, electrical conductivity, available potassium, alkaline phosphatase and sucrase activity (r>0.44, P<0.05). Soil pH was extremely significantly positively correlated with available potassium and electrical conductivity (r>0.55, P<0.01), indicating that the various improvement measures to alleviate soil acidification were significantly correlated with the increase in the total water-soluble salt ion content in the soil.

[0126] Table 8 Correlation between soil quality comprehensive index and various indicators

[0127]

[0128] Note: ** indicates that the correlation is significant at the 0.01 level; * indicates that the correlation is significant at the 0.05 level.

[0129] Soil acidification can cause soil compaction, poor aeration, reduced soil enzyme activity, and reduced soil nitrogen and phosphorus effectiveness, leading to reduced soil quality and threatening crop safety production. The results of this experiment show that the application of biochar and carbon-adsorbed polyglutamic acid can significantly increase soil pH, increase soil salt content, and alleviate soil acidification. After soil acidification, phosphate ions are easily reacted with Fe 3+ and Al3+ The metal ions react to form insoluble iron phosphate and aluminum phosphate, resulting in soil phosphorus deficiency. The application of biochar and charcoal-adsorbed polyglutamic acid can synergistically increase the activity of soil sucrase and urease and the content of available phosphorus in the soil, indicating that the application of the two can promote soil carbon and nitrogen transformation and improve the effectiveness of soil phosphorus. The application of biochar and charcoal-adsorbed polyglutamic acid can significantly increase soil pH, electrical conductivity, available potassium, microaggregate ratio, and soil sucrase and urease activities, indicating that the application of the two can improve soil structure, increase soil salt content, alleviate soil acidification, increase soil enzyme activity and nutrient effectiveness, and thus improve soil quality by 46%. This study confirmed that the application of biochar and charcoal-adsorbed polyglutamic acid has the best effect on improving the quality of acidic soils, but the effect of the application of the two on the production of acidic farmland crops needs further study.

[0130] Experimental Example 2 Effects of biochar and charcoal-adsorbed polyglutamic acid on wheat yield and quality in acidic farmland in southern Henan

[0131] 1. Test materials

[0132] The field test site is located in Xiping County, Zhumadian City, Henan Province (33°10′N, 113°36′E), which is a transition zone from the northern subtropical zone to the warm temperate zone. The climate belongs to the subhumid continental monsoon climate, with an average annual temperature of 14.8℃ and a rainfall of 852mm. The local planting method is a typical winter wheat / summer corn rotation system. The test soil type is yellow-brown soil, with a clay content of 35%, a soil pH of 3.74, organic matter of 12.2g / kg, total nitrogen of 0.77g / kg, available phosphorus of 55.97mg / kg, and available potassium of 17.36mg / kg.

[0133] The test carbon adsorbed polyglutamic acid was provided by Henan Naian Biotechnology Co., Ltd. The carbon adsorbed polyglutamic acid content was ≥10g / kg, the organic matter content was ≥80g / kg, and the pH value was 4.3; the biochar was corn straw charcoal, the pyrolysis temperature was 450℃~650℃, the pH value was 9.65, the total carbon was 507g / kg, the total nitrogen was 2.10g / kg, the total phosphorus was 8.37g / kg, and the total potassium was 9.33g / kg.

[0134] 2. Field trial design

[0135] Severely acidic farmland in southern Henan was selected for field experiments, and the treatments were as follows:

[0136] ①CK: control, farmers routinely applied nitrogen, phosphorus and potassium fertilizer (N-P2O5-K2O: 26-10-4) 45kg / mu;

[0137] ② Treatment C: NPK fertilizers were the same as the control, plus biochar was applied at 2666.8 kg / mu before winter wheat tillage and then tilled into the soil;

[0138] ③ Treatment E: NPK fertilizers were the same as the control, and 6.75 kg / mu of carbon-absorbed polyglutamic acid was applied twice, at the seedling stage and green stage of winter wheat, with each application amount of 3.375 kg / mu dissolved in 350L of water and sprayed evenly;

[0139] ④ Treatment CE: NPK fertilizers were the same as those of the control, plus biochar (933.38 kg / mu) and carbon-absorbed polyglutamic acid (2.025 kg / mu). The biochar application method was the same as that of treatment C. Carbon-absorbed polyglutamic acid was applied twice at the seedling stage and green stage of winter wheat, with each application amount of 1.013 kg / mu dissolved in 350 L of water and sprayed evenly.

[0140] Four treatments, three replicates per treatment, randomized block arrangement, plot area 90m 2 , with 1m protection between plots. Wheat was planted on November 9, 2022. The wheat variety was Tianning 38, and the sowing rate was 38-40 catties / mu. Sampling was carried out during the winter wheat harvest in May 2023. Three samples were taken for each treatment. Ten wheat plants and surface soil (0-20 cm) were randomly dug up with roots for each sample for experimental use. The test soil samples were air-dried and used for the determination of pH, soil base ion content, nutrients, enzyme activity and other indicators. The plant samples after drying were crushed and sieved for the determination of plant nutrient content. Wheat grains were powdered separately for the determination of quality indicators such as crude protein and gluten content of wheat grains.

[0141] 3. Index determination method

[0142] (1) Determination of soil physical and chemical properties

[0143] Soil pH was determined using a water-soil ratio of 1:5; soil exchangeable acid was determined using the KCl exchange-neutralization titration method; soil base ion was determined using the ammonium acetate exchange-atomic absorption spectrophotometry method; soil organic matter was determined using the potassium dichromate volumetric method-external heating method; soil total nitrogen was determined using the semi-micro Kjeldahl method; available potassium was determined using the NH4OAc extraction-flame photometer method; available phosphorus was determined using the molybdenum antimony colorimetric method; soil urease activity was determined using the sodium phenol colorimetric method; soil acid phosphatase activity was determined using the disodium phenyl phosphate colorimetric method; soil cellulase activity was determined using the nitrosalicylic acid colorimetric method.

[0144] (2) Determination of wheat yield and quality

[0145] Three sample points were randomly selected for each treatment, and 25 rows were measured at each sample point to calculate the average row spacing, and the calculation formula was: 25 row width / 24; one-meter double rows were selected at each sample point to investigate the number of ears per mu, and 20 ears were randomly selected in each sample section to investigate the number of grains per ear; number of ears per mu (10,000) = number of ears per one-meter double row (ears) / (11 row spacing × 3); actual yield (kg / mu) = number of ears per mu (10,000) × number of grains per ear (ear) × 1000-grain weight (g) × 0.85; biomass (g) = mass of the plant after drying (g); root-to-crown ratio (%) = plant underground biomass / plant aboveground biomass × 100%; the crude protein content of wheat grains was determined by the Kjeldahl nitrogen method, and the crude gluten content of wheat was determined by the hand-washed gluten method.

[0146] (3) Determination of plant nutrient indicators

[0147] The nitrogen content of the plants was determined by the semi-micro Kjeldahl method, the phosphorus content was determined by the vanadium-molybdenum-yellow colorimetric method, the potassium and sodium contents were determined by the flame photometer method, and the calcium and magnesium contents were determined by the atomic absorption spectrophotometer method.

[0148] (4) Data processing

[0149] SPSS26.0 was used for one-way ANOVA and correlation analysis, and Duncan was used to test the significant differences among treatments in variance analysis. Origin2021 was used for drawing.

[0150] 4. Results Analysis

[0151] (1) Wheat production

[0152] As shown in Table 9, compared with the control, treatments C, E and CE significantly increased wheat yield, ear number per mu, number of grains per ear, and biomass (P<0.05); treatments C, E and CE increased yield by 25%, 18%, and 26%, respectively. Treatment CE significantly increased wheat thousand-grain weight (P<0.05), and treatment E significantly increased wheat root-shoot ratio (P<0.05).

[0153] Table 9 Wheat yield

[0154]

[0155] Note: Data are mean ± standard error, different letters indicate significant differences among treatments (P<0.05). CK: control C: biochar E: charcoal-adsorbed polyglutamic acid; CE: biochar and charcoal-adsorbed polyglutamic acid at reduced application rates. ***P<0.001, **P<0.01, *P<0.05, ns indicates no significant difference. Same below.

[0156] (2) Wheat quality

[0157] Wheat quality traits such as grain crude protein content and gluten content have a great influence on wheat processing performance. Wheat grain protein affects the elasticity and extensibility of dough, affects the quality and strength of dough gluten, and also plays a decisive role in flour processing quality. As shown in Table 10, compared with the control, the crude protein content of wheat grains in treatments C, E and CE increased by 76%, 55% and 77%, respectively. The gluten content of wheat directly affects the viscosity, elasticity and baking quality of dough, and the wet gluten content of treatments containing E (treatments E and CE) was significantly increased.

[0158] Table 10 Wheat quality

[0159]

[0160] (3) Plant nutrient content

[0161] like Figure 2 As shown in the figure, compared with the control, the nitrogen content of the root system in treatment C increased by 69%; the nitrogen content of the aboveground parts in treatments C, E and CE decreased significantly, which may be due to the transfer of aboveground nitrogen to the grain during maturity. Treatments C, E and CE significantly increased the phosphorus content in the root system, and the increasing effect of treatments E and CE was more significant, increasing by 57% and 58%, respectively; treatments C, E and CE significantly increased the aboveground phosphorus content of the plant, and the aboveground phosphorus content of treatment CE was the highest. Treatments C and CE significantly increased the aboveground sodium content. Treatments E and CE significantly increased the calcium content in the root system, increasing by 28% and 83%, respectively; the aboveground calcium content of treatments C, E and CE increased significantly, and the aboveground calcium content of treatments E and CE increased more significantly (P<0.05). The magnesium content in the root system of treatments E and CE increased by 103% and 192%, respectively; treatment CE significantly increased the aboveground magnesium content (P<0.05).

[0162] (4) Soil pH and exchangeable acid

[0163] Soil pH reflects the hydrogen ions in the soil solution and is an active acid. Soil exchange acid refers to the hydrogen ions and aluminum ions adsorbed on the soil colloids and is a potential acid. The two are in dynamic equilibrium. Too low soil pH will lead to soil nutrient imbalance and reduced soil fertility. As shown in Table 11, treatment C significantly increased soil pH and reduced the total amount of soil exchange acid and exchange hydrogen content (P<0.05). Treatments E and CE had no significant effect on the total amount of soil exchange acid and exchange hydrogen content.

[0164] Table 11 Soil pH and exchangeable acid

[0165]

[0166] (5) Soil exchange base ions, cation exchange capacity and base ion saturation

[0167] As shown in Table 12, both treatments C and CE significantly increased the exchangeable potassium and sodium contents in the soil (P<0.05), and the combined application of the two had a more significant effect. Both treatments E and CE significantly increased the exchangeable magnesium content; only treatment C significantly increased base saturation (P<0.05).

[0168] Table 12 Soil exchangeable base ions, soil cation exchange capacity and base saturation

[0169]

[0170] (6) Soil organic matter, total nitrogen, available phosphorus, and available potassium content

[0171] The results are shown in Table 13. It can be seen that compared with the control, treatment C significantly increased the contents of soil organic matter, total nitrogen, available phosphorus and available potassium, which increased by 37%, 26%, 35% and 106%, respectively. Treatment CE significantly increased the contents of soil total nitrogen and available potassium (P<0.05).

[0172] Table 13 Total nitrogen, available phosphorus and available potassium content of soil organic matter

[0173]

[0174] (7) Soil enzyme activity

[0175] Soil cellulase, urease, and acid phosphatase are important enzymes for the transformation of carbon, nitrogen, and phosphorus in the soil, respectively, and affect the soil carbon decomposition and the supply capacity of nitrogen and phosphorus nutrients. As shown in Table 14, treatments C, E, and CE all significantly increased the activities of soil urease and cellulase, and treatments E and CE significantly increased the activity of acid phosphatase by 20% and 24%, respectively; treatments C and CE increased the activity of cellulase by 24% and 32%, respectively.

[0176] Table 14 Soil enzyme activity

[0177]

[0178] (8) Correlation between wheat yield and quality and soil indicators

[0179] like Figure 3 As shown in the figure, wheat yield was significantly positively correlated with the number of ears per mu, the number of grains per ear, the nitrogen and phosphorus content of the root system, cellulase, urease, and acid phosphatase (P<0.05), and the crude protein in wheat grains was significantly positively correlated with the nitrogen, phosphorus, and calcium content of the root system, Soil cellulase and urease showed significant Positive correlation, wheat gluten content and thousand-grain weight, root calcium and magnesium content, There was a significant positive correlation between soil acid phosphatase and soil acid phosphatase (P<0.05).

[0180] The results of this experiment show that the single application of biochar and charcoal-absorbed polyglutamic acid and the combination of the two at reduced dosage can significantly increase wheat yield, increasing by 25.2%, 17.7%, and 26.2%, respectively. Treatments C, E, and CE significantly increased wheat grain crude protein by 75.5%, 55%, and 77.1%, respectively, and treatments E and CE significantly increased wheat gluten content. Biochar mainly increased soil organic matter and base saturation, reduced soil pH and exchange acid, and alleviated soil acidification; biochar significantly increased soil urease and cellulase activities, promoted root nitrogen absorption, and increased the number of wheat ears per mu, the number of grains per ear, and the content of grain protein, thereby increasing wheat yield and quality. Carbon-absorbed polyglutamic acid significantly increased soil acid phosphatase activity, promoted root phosphorus, calcium, and magnesium absorption, and increased gluten content, thereby improving wheat quality. The combination of biochar and carbon-absorbed polyglutamic acid at reduced dosage synergistically enhanced soil enzyme activity, promoted root nitrogen, phosphorus, calcium, and magnesium absorption, and increased the number of ears per mu, the number of grains per ear, thousand-grain weight, grain protein, and gluten content, thereby increasing wheat yield and quality.

[0181] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An acidic soil conditioner, characterized in that: The acidic soil conditioner comprises the following raw materials: carbon-adsorbed polyglutamic acid and biochar; the mass ratio of the carbon-adsorbed polyglutamic acid to the biochar is 1:200-800.

2. The acidic soil conditioner according to claim 1, characterized in that The pH value of the carbon adsorbing polyglutamic acid is 4-5.

3. The acidic soil conditioner according to claim 1, characterized in that: The biochar includes straw biochar.

4. Use of the acidic soil conditioner according to any one of claims 1 to 3 in improving acidic soil.

5. The use according to claim 4, characterized in that: The acidic soil includes yellow-brown soil, sandy ginger black soil, brick red soil, red soil, red soil or yellow soil.

6. A method for improving acidic farmland soil-crop system, characterized in that: The method comprises applying the acidic soil conditioner according to any one of claims 1 to 3 to acidic farmland soil.

7. The method according to claim 6, characterized in that The biochar in the acidic soil conditioner is applied before soil rotary tillage and then rotary tilled into the soil.

8. The method according to claim 6, characterized in that The carbon-adsorbed polyglutamic acid in the acidic soil conditioner is dissolved in water and sprayed.

9. The method according to claim 6, characterized in that The application amount of the acidic soil conditioner is 700-1300 kg / mu.

10. Use of the acidic soil conditioner according to any one of claims 1 to 3 or the acidic farmland soil-crop system improvement method according to any one of claims 6 to 9 in improving soil quality and / or improving crop quality and yield.

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