Application of chitosan-betaine mixture in prevention and control of soil nitrate nitrogen leaching and method for prevention and control of soil nitrate nitrogen leaching

Abstract

The invention belongs to the technical field of farmland soil remediation, and particularly relates to application of a chitosan-betaine mixture in prevention and control of soil nitrate nitrogen leaching and a method for prevention and control of soil nitrate nitrogen leaching. The invention provides an application of a chitosan-betaine mixture in prevention and control of soil nitrate nitrogen elution. The chitosan-betaine mixture comprises chitosan and betaine. The mass ratio of the chitosan to the betaine is (1-20): (80-99). The chitosan-betaine mixture provided by the invention is associated with chitosan and betaine monomers in a local structure, and nitrate nitrogen in soil is adsorbed and chelated by utilizing positive charges and hydrogen-bond interaction on molecules of the mixture, so that leaching of the nitrate nitrogen is reduced, downward movement of the nitrate nitrogen in the soil is controlled, the nitrate nitrogen is accumulated in the soil and crop root layers, and the soil quality is improved. Therefore, the utilization efficiency of the nitrogen fertilizer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of farmland soil restoration, and particularly relates to an application of a chitosan-betaine mixture in preventing and controlling soil nitrate nitrogen leaching, and a method for preventing and controlling soil nitrate nitrogen leaching. Background Art

[0002] The leaching of nitrate nitrogen from soil in farmland is one of the main ways of nitrogen fertilizer loss and the main source of groundwater pollution. The leaching of nitrate nitrogen from farmland has always been a matter of great concern and a current research hotspot. There is no immediate solution to this problem. People mainly reduce the input of nitrogen fertilizer and the downward movement of nitrate nitrogen by formulating scientific and reasonable fertilization and irrigation strategies. In addition, the application of urease inhibitors and nitrification inhibitors can slow down the hydrolysis of urea and the conversion of nitrogen, thereby reducing the production and leaching of nitrate nitrogen to a certain extent.

[0003] The principle of urease inhibitors and nitrification inhibitors to inhibit nitrate nitrogen leaching is to apply a certain amount of urease inhibitors to the soil to inhibit the conversion of nitrogen in urea into ammonium nitrogen, and then use nitrification inhibitors to inhibit the conversion of ammonium nitrogen into nitrate nitrogen. In the above process, nitrate nitrogen is released slowly and in small amounts, so the amount of leaching is relatively less than normal fertilization.

[0004] Intercropping some leguminous crops or filler crops such as corn can also remove some of the quick-acting nitrogen in the soil and reduce leaching. The principle of leguminous crops controlling the leaching of nitrate nitrogen is mainly that the roots of leguminous crops can form nodules, which fix a certain amount of nitrogen in the soil. However, the total amount of nitrogen fixed by the roots of leguminous crops is not high, about 6 to 13 kg per hectare. Moreover, nodule nitrogen fixation has no specific requirements for the form of nitrogen. Not only nitrate nitrogen, but other forms of nitrogen can be fixed.

[0005] However, the above method will still cause some nitrate nitrogen to enter the soil without being fixed, and this part of nitrate nitrogen entering the soil still has the risk of leaching. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide an application of a chitosan-betaine mixture in preventing and controlling the leaching of nitrate nitrogen from soil, and a method for preventing and controlling the leaching of nitrate nitrogen from soil. The chitosan-betaine mixture can prevent and control the downward leaching of nitrate nitrogen in the soil and has a good prevention and control effect.

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

[0008] The invention provides application of a chitosan-betaine mixture in controlling soil nitrate nitrogen leaching. The chitosan-betaine mixture comprises chitosan and betaine; the mass ratio of the chitosan to the betaine is (1-20):(80-99).

[0009] Preferably, the molecular weight of the chitosan is 100,000 to 300,000 Da.

[0010] Preferably, the preparation method of the chitosan-betaine mixture is:

[0011] dissolving chitosan in a mixture of acetic acid and citric acid to protonate chitosan to form a protonated chitosan solution;

[0012] The aqueous solution of betaine is mixed with the protonated chitosan solution to obtain a chitosan-betaine mixture.

[0013] Preferably, the mass concentration of betaine in the aqueous solution of betaine is 5 to 50%.

[0014] Preferably, the mass ratio of acetic acid to citric acid is (1-10):1.

[0015] Preferably, the mass concentration of chitosan in the protonated chitosan solution is 0.1-4%.

[0016] The present invention also provides a method for preventing and controlling soil nitrate leaching, comprising the following steps:

[0017] The chitosan-betaine mixture or a mixture of the chitosan-betaine mixture and a fertilizer is applied to the soil.

[0018] Preferably, the application location depth is 0 to 40 cm.

[0019] Preferably, the application method includes drip irrigation or watering.

[0020] Preferably, the chitosan-betaine mixture is applied in an amount of 1 to 10 kg / mu / time, and is applied 1 to 3 times per growing season.

[0021] The present invention provides the use of a chitosan-betaine mixture in controlling the leaching of nitrate nitrogen in soil, wherein the chitosan-betaine mixture includes chitosan and betaine; the mass ratio of the chitosan and betaine is (1-20):(80-99). The chitosan-betaine mixture provided by the present invention has positive charges and hydrogen bonds on its molecules, and utilizes the positive charges and hydrogen bonds to adsorb and chelate nitrate nitrogen in the soil, thereby reducing the leaching of nitrate nitrogen in the soil, controlling the downward movement of nitrate nitrogen in the soil, and accumulating nitrate nitrogen in the soil and in the root layer of crops for absorption and utilization by crops, thereby improving the utilization efficiency of nitrogen fertilizer. Moreover, chitosan and betaine are both naturally degradable and environmentally friendly polymer compounds, and the two are compounded in a reasonable ratio as a nitrogen fertilizer synergist, achieving a good blocking effect, while greatly reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The graphs of the changes in nitrate nitrogen concentration of different chitosan-betaine mixtures with increasing soil leaching times are shown;

[0023] Figure 2 This is the effect of different chitosan-betaine mixtures on the total nitrogen leaching of potted grapes;

[0024] Figure 3 This is a graph showing the effect of different chitosan-betaine mixtures on nitrogen utilization efficiency of potted grape plants;

[0025] Figure 4 The infrared spectra of chitosan, betaine and chitosan-betaine mixture are compared, wherein a is the infrared spectrum of chitosan, b is the infrared spectrum of betaine, and c is the infrared spectrum of chitosan-betaine mixture. DETAILED DESCRIPTION

[0026] The invention provides application of a chitosan-betaine mixture in controlling soil nitrate nitrogen leaching. The chitosan-betaine mixture comprises chitosan and betaine; the mass ratio of the chitosan to the betaine is (1-20):(80-99).

[0027] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.

[0028] In the present invention, the chitosan-betaine mixture comprises chitosan and betaine; the mass ratio of chitosan to betaine is (1-20):(80-99), preferably (5-10):(90-95), and most preferably 1:5 or 1:10.

[0029] In the present invention, the molecular weight of the chitosan is preferably 100,000 to 300,000 Da, more preferably 150,000 to 250,000 Da; the deacetylation degree of the chitosan is 90%. The chitosan used in the present invention is chitosan with a deacetylation degree of 90% extracted from crab shells and shrimp shells, and its structure is shown below:

[0030]

[0031] In the present invention, the molecular weight of betaine is 117.15, and there is no net charge on the surface of betaine, but the molecule contains -COO - 、-(CH 3 ) 3 N + When betaine and chitosan are mixed, they can form hydrogen bonds through the electron attraction of carbon, hydrogen and oxygen. Betaine is adsorbed on the long-chain chitosan molecules. The structure of betaine is shown below:

[0032]

[0033] In the present invention, the preparation method of the chitosan-betaine mixture is preferably:

[0034] dissolving chitosan in a mixture of acetic acid and citric acid to protonate chitosan to form a protonated chitosan solution;

[0035] The aqueous solution of betaine is mixed with the protonated chitosan solution to obtain a chitosan-betaine mixture.

[0036] The invention dissolves chitosan in a mixture of acetic acid and citric acid for protonation to form a chitosan protonation solution.

[0037] In the present invention, the mass ratio of acetic acid to citric acid is preferably (1-10):1, more preferably (2-6):1, and most preferably 5:1; the mass concentration of chitosan in the protonated chitosan solution is preferably 0.1-4%, more preferably 0.5-3%, and most preferably 3%. The present invention has no particular limitation on the dissolution process, and the chitosan can be completely dissolved in the mixture of acetic acid and citric acid using a dissolution process well known in the art.

[0038] Chitosan cannot be directly dissolved in water. The present invention uses dilute acid to protonate chitosan before it can be dissolved in water.

[0039] Protonation is the process by which an atom, molecule, or ion acquires a proton (H + The process of NH in chitosan molecules can be simply understood as combining with protons, that is, combining with a proton. 2 Only after combining with protons can it become NH 3 + The chitosan in the chitosan protonated solution of the present invention is a cationic polysaccharide containing a positive charge, and the protonated molecules can form more cationic NH 3 + .

[0040] After obtaining the protonated chitosan solution, the present invention mixes the aqueous solution of betaine with the protonated chitosan solution to obtain a chitosan-betaine mixture.

[0041] In the present invention, the mass concentration of betaine in the betaine aqueous solution is preferably 5-50%, more preferably 10-40%, and most preferably 20%. The present invention has no special limitation on the mixing process, and the materials can be mixed uniformly using a mixing process well known in the art.

[0042] The chitosan-betaine mixture provided by the present invention has positive charges and hydrogen bonds on its molecules, and utilizes the positive charges and hydrogen bonds to adsorb and chelate nitrate nitrogen in the soil, thereby reducing the leaching of nitrate nitrogen in the soil, controlling the downward movement of nitrate nitrogen in the soil, and accumulating nitrate nitrogen in the soil and in the root layer of crops for absorption and utilization by crops, thereby improving the utilization efficiency of nitrogen fertilizer. Moreover, chitosan and betaine are both natural, degradable and environmentally friendly high molecular compounds, and the two are compounded in a reasonable ratio as a nitrogen fertilizer synergist, achieving a good barrier control effect, while greatly reducing the cost.

[0043] The present invention also provides a method for preventing and controlling soil nitrate nitrogen leaching, which is characterized by comprising the following steps:

[0044] The chitosan-betaine mixture or a mixture of the chitosan-betaine mixture and a fertilizer is applied to the soil.

[0045] In the present invention, the application amount of the chitosan-betaine mixture is preferably 1 to 10 kg / mu / time, applied 1 to 3 times per growing season, more preferably 2 to 6 kg / mu / time, applied 1 to 3 times per growing season. The present invention has no particular limitation on the application amount and application frequency of the chitosan-betaine mixture, which can be determined according to the content of nitrate nitrogen in the soil. In an embodiment of the present invention, the application amount of the chitosan-betaine mixture is 2.5 to 5 kg / mu / time.

[0046] The present invention has no special restrictions on the type and amount of the fertilizer in the mixture of the chitosan-betaine mixture and the fertilizer, and can be selected according to actual needs.

[0047] In the present invention, the depth of the soil at the application location is preferably 0 to 40 cm, more preferably 0 to 20 cm.

[0048] In the present invention, the application method includes drip irrigation or watering; the watering is preferably directly watering the part where the fibrous roots gather under the tree tray.

[0049] The present invention has no special limitation on the soil conditions when the chitosan-betaine mixture is applied, and the soil conditions can be determined according to the actual situation.

[0050] In the present invention, the soil preferably includes grape-growing soil or tomato-growing soil, more preferably grape-growing soil.

[0051] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] In the experiment, chitosan-betaine mixtures (CTS-GB) with different mass ratios were added to the soil in the soil column, which were marked as CTS-GB (mass ratio of chitosan and betaine was 1:70), CTS-GB2 (mass ratio of chitosan and betaine was 1:50), CTS-GB3 (mass ratio of chitosan and betaine was 1:30), CTS-GB4 (mass ratio of chitosan and betaine was 1:10), CTS-GB5 (mass ratio of chitosan and betaine was 1:5), and CTS-GB6 (mass ratio of chitosan and betaine was 1:1). The soil without any substance added was used as the control. The mass ratio of acetic acid to citric acid is 5:1, the mass concentration of chitosan in the protonated chitosan solution is 3%, the molecular weight of chitosan is 200,000 Da, the mass concentration of betaine in the betaine solution is 20%, and 0-10cm, 10-20cm, 20-30cm, and 30-40cm soils are taken from the grape cultivation facilities, and the chitosan and betaine mixtures of CTS-GB1, CTS-GB2, CTS-GB3, CTS-GB4, CTS-GB5, and CTS-GB6 are mixed with 0-40cm soil in layers, and the application amount of the chitosan-betaine mixture is 0.1g / kg air-dried soil. The soil is loaded into a soil column with a leaching device, and water is added from the upper part of the soil column for leaching regularly. The leaching liquid is collected in a liquid collection bottle at the bottom of the soil column. When the leaching liquid is full of 200mL, another liquid collection bottle is replaced until the concentration of nitrate nitrogen in the leaching liquid stabilizes at a lower concentration. The results are as follows Figure 1 shown.

[0054] Figure 1 The test results show that the nitrate-nitrogen concentration in the initial soil leaching solution of the treatment without adding compound substances (control) reached 1600 mg / kg. After adding different compound substances to the soil, the nitrate-nitrogen concentration in the initial soil leaching solution of the soil treated with each compound ratio was significantly reduced compared with the control, with the CTS-GB5 treatment having the largest reduction. As the leaching time increased, the nitrate-nitrogen concentration in the soil leaching solution treated with CTS-GB5 was always the lowest, indicating that CTS-GB5 has the greatest blocking effect on the leaching of soil nitrate-nitrogen.

[0055] Example 2

[0056] In the rain shelter, Kyoho grapes were planted in pots with a height of 50 cm and a diameter of 30 cm. Soil from the vineyard with a layer of soil of 0-40 cm was taken every 10 cm. Each layer of soil was mixed evenly with chitosan-betaine compound (CTS-GB) in different proportions. The soil was then placed in the pots in the order of the original soil layers. When 15-20 cm of soil was filled, one-year-old Kyoho grape seedlings were planted, and then an appropriate amount of clean water was poured in until no water flowed out from under the pots. In the experiment, different proportions of CTS-GB (mass ratio of chitosan and betaine is 1:70), CTS-GB2 (mass ratio of chitosan and betaine is 1:50), CTS-GB3 (mass ratio of chitosan and betaine is 1:30), CTS-GB4 (mass ratio of chitosan and betaine is 1:10), CTS-GB5 (mass ratio of chitosan and betaine is 1:5), and CTS-GB6 (mass ratio of chitosan and betaine is 1:1) were added to the soil in the pot, and the soil without any substance was used as the control. Among them, the mass ratio of acetic acid and citric acid was 5:1, the mass concentration of chitosan in the protonated chitosan solution was 3%, and the mass concentration of betaine in the betaine solution was 20%, and the potted soil without any substance was used as the control. The application amount of chitosan-betaine mixture was 0.7g / kg air-dried soil. After the grape seedlings germinate, 22g+ of ordinary urea is applied to each pot. 15 When the new shoots of the grape seedlings reach 20 cm, the amount of water is increased by more than 2 times each time. After each irrigation, the solution leaking from the bottom of the pot is collected in a container and the mass of the collected solution is calculated. Figure 2 As shown, the nitrate nitrogen content in the solution was determined, and the 15 The abundance of N was used to calculate the nitrogen utilization rate. The results are as follows Figure 3 shown.

[0057] Figure 2 and Figure 3 The test results show that adding different proportions of CTS-GB compound to potting soil has a significant effect on the growth of potted grapes. The biomass of potted grapes treated with CTS-GB5 was the highest, 33.5% higher than the control, followed by CTS-GB6 and CTS-GB4, with grape biomass 19.8% and 15.6% higher than the control, respectively. 15 The N utilization rate of grape plants treated with CTS-GB5 was the highest, reaching 24.16%, 86.17% higher than the control. The total amount of nitrate nitrogen in the leaching solution of the soil in each treatment was the highest in the control, and the lowest in the CTS-GB5 treatment, which was 66.6% lower than the control. The total amount of nitrate nitrogen leaching in potted soil treated with CTS-GB6 and CTS-GB4 was also low, 44.4% and 38.8% lower than the control, respectively. This shows that the CTS-GB compound has a significant inhibitory effect on the loss of soil nitrate nitrogen leaching.

[0058] Example 3

[0059] Chitosan-betaine mixture test was conducted in a vineyard with normal growth and fruiting in the field. CTS-GB5 was used as the treatment, and Kyoho grapes without any additions were used as the control. Normal fruiting grapevines were selected as test materials, with 16 plants in one plot, single vine, and each plot was 24m 2 , repeated 3 times. CTS-GB5 (the mass ratio of chitosan and betaine is 1:5, the mass ratio of acetic acid and citric acid is 5:1, the mass concentration of chitosan in the protonated chitosan solution is 3%, and the mass concentration of betaine in the betaine solution is 20%), was applied 3 times during the grape growing season, in mid-June, mid-July and mid-August, respectively, after the grapes were top-dressed. The application rate of the chitosan-betaine mixture is 2.5kg / mu / time, diluted 100 times with water and evenly poured into the fertilization position under the tree. Other fertilization, pest control and irrigation measures are consistent. The yield of grapes and the content of nitrate nitrogen in the soil at 0-20cm, 20-40cm, 40-60cm, 60-80cm and 80-100cm were investigated.

[0060] The results of the field grape test showed that the application of CTS-GB5 to the root zone of grapes increased the grape yield by 15.8% compared with the control, and the grapes grew robustly with dark green leaves. The fruit tasted good and was larger, and the soluble solids in the fruit were 2 degrees higher than the control. The nitrate nitrogen in the soil was mainly concentrated in the 0-40cm soil layer, while the nitrate nitrogen in the control soil moved downward significantly, mainly concentrated in the 60-80cm soil layer, with a significant risk of leaching.

[0061] Example 4

[0062] Chitosan-betaine mixture test was conducted in the vineyards with normal growth and fruiting in the field. CTS-GB5 (mass ratio of chitosan to betaine is 1:5) was used as the treatment, in which the mass ratio of acetic acid to citric acid was 5:1, the mass concentration of chitosan in the chitosan protonated solution was 3%, and the mass concentration of betaine in the betaine solution was 20%. The control was not added with any substance. Normally fruiting Liaofeng grapevines were selected as test materials, with 16 plants in one plot, single vine, and each plot was 24m 2 , repeated 3 times. CTS-GB5 was applied twice during the grape growing season, in mid-June and late July, after grape topdressing. The application rate of chitosan-betaine mixture was 5kg / mu / time, diluted 100 times with water and evenly poured into the fertilization location under the tree. Other fertilization, pest control and irrigation measures were consistent. The yield of grapes and the content of nitrate nitrogen in the soil at 0-20cm, 20-40cm, 40-60cm, 60-80cm and 80-100cm were investigated.

[0063] The results of the field grape test showed that the application of CTS-GB5 to the root zone of grapes increased the grape yield by 15.8% compared with the control, and the grapes grew robustly with dark green leaves. The fruit tasted good and was firm, and the soluble solids in the fruit were 2 degrees higher than the control. During the fruit expansion period, there were no physiological disease reactions such as leaf vein chlorosis or edge scorch caused by soil fertilization, while the grapes in the control area had physiological diseases of varying degrees. After the application of CTS-GB5, the nitrate nitrogen in the soil was mainly concentrated in the 0-40cm soil layer, while the nitrate nitrogen in the control soil moved downward significantly, mainly concentrated in the 60-100cm soil layer, with a significant risk of leaching.

[0064] Example 5

[0065] In the tomato greenhouse, a chitosan-betaine mixture test was carried out. CTS-GB5 (the mass ratio of chitosan and betaine is 1:5, the mass ratio of acetic acid and citric acid is 5:1, the mass concentration of chitosan in the chitosan protonated solution is 3%, and the mass concentration of betaine in the betaine solution is 20%), and no substance is added as a control. The greenhouse is 70 meters long and 10 meters wide, with two rows of tomatoes planted in each ridge, with a spacing of 40 cm. 3 ridges make up 1 plot, which is repeated 3 times. CTS-GB5 was applied 3 times during the tomato growing season, which was applied after the first flowering, the second fertilization, and the third fertilization. The application amount of the chitosan-betaine mixture is 3kg / mu / time, mixed in the drip irrigation water, and dripped to the roots of tomatoes. Other fertilization, pest control and irrigation measures are consistent. Investigate the tomato yield and the nitrate nitrogen content in the soil at 0-20cm, 20-40cm, 40-60cm, 60-80cm, and 80-100cm.

[0066] The results of the tomato test showed that the tomato yield was 17.5% higher than the control when CTS-GB5 was applied through drip irrigation. The tomato leaves were dark green and normal, and there were no diseases or insect pests. The nitrate nitrogen in the soil was mainly concentrated in the 20-50cm soil layer, while the nitrate nitrogen in the control soil moved downward significantly, mainly concentrated in the 60-80cm soil layer, with a significant risk of leaching.

[0067] Performance Testing

[0068] Figure 4 The infrared spectra of chitosan, betaine and chitosan-betaine mixture are compared, where a is the infrared spectrum of chitosan, b is the infrared spectrum of betaine, and c is the infrared spectrum of chitosan-betaine mixture.

[0069] Depend on Figure 4 It can be seen that the infrared spectrum analysis of chitosan shows that its -1 The strong and wide bands appearing on the left and right ( Figure 4a), which is the superposition of the stretching vibration peak of the intermolecular hydrogen bond OH and the stretching vibration peak of NH. 2358.22cm -1 、2350.15cm -1 There are two peaks close to each other, which are the stretching vibration absorption peaks of CH, 2060.39cm -1 A shoulder peak appears at 2 NH. 1654.71cm -1 、1631.97cm -1 There are two peaks close to each other, which are the stretching vibration of CO and the bending vibration of NH in the amide. The infrared spectrum of betaine ( Figure 4 b) in the figure has no NH bond stretching vibration, only at 3504-3389cm -1 The narrow shoulder peaks on the left and right are the stretching vibration peaks of OH and CO. -1 、2342.15cm -1 The double peaks at 1631.97cm are quite obvious. -1 A peak appears.

[0070] Compare the infrared spectra of the mixture ( Figure 4 c) The analysis results show that after adding betaine to chitosan, 3626.6cm -1 The peak at 3496.76-3396.99cm -1 , and the peak amplitude becomes smaller and the peak becomes sharper. This may be due to the association of some groups, the weakening of the intermolecular hydrogen bond OH, and the change in the bond length, which leads to the change of the peak, mainly manifested in the stretching vibration of CO and NH. -1 、2350.15cm -1 There are two relatively close peaks at 1654.71cm -1 、1631.97cm -1 The double peaks at 1548.34, 1540.27, 1502.12, 1471.31, 1448.57, 1418.49, 1395.02, and 134.471 showed dense peaks, which were due to the overlap of the absorption peak formed by NH bending vibration and the absorption peak of antisymmetric stretching vibration of carboxyl anion, the stretching vibration peak of CN, and the symmetric stretching vibration of carboxyl anion.

[0071] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. Application of chitosan-betaine mixture in controlling soil nitrate leaching, characterized in that: The chitosan-betaine mixture comprises chitosan and betaine; the mass ratio of the chitosan to betaine is (1-20):(80-99).

2. The use according to claim 1, characterized in that: The molecular weight of the chitosan is 100,000 to 300,000 Da.

3. The use according to claim 1, characterized in that: The preparation method of the chitosan-betaine mixture is: dissolving chitosan in a mixture of acetic acid and citric acid to perform protonation to form a chitosan protonated solution; The aqueous solution of betaine is mixed with the protonated chitosan solution to obtain a chitosan-betaine mixture.

4. The use according to claim 3, characterized in that: The mass concentration of betaine in the betaine aqueous solution is 5-50%.

5. The use according to claim 3, characterized in that: The mass ratio of the acetic acid to the citric acid is (1-10):

1.

6. The use according to claim 3, characterized in that: The mass concentration of chitosan in the protonated chitosan solution is 0.1-4%.

7. A method for preventing and controlling soil nitrate leaching, characterized in that: The following steps are involved: The chitosan-betaine mixture or a mixture of the chitosan-betaine mixture and a fertilizer is applied to the soil.

8. The method according to claim 7, characterized in that The application location depth is 0 to 40 cm.

9. The method according to claim 7, characterized in that: The application method includes drip irrigation or pouring.

10. The method according to claim 7, characterized in that The chitosan-betaine mixture is applied in an amount of 1 to 10 kg / mu / time, and is applied 1 to 3 times in each growing season.

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