Saline-alkali soil salinity and nitrate environmental risk cooperative control method

Abstract

The invention provides a saline-alkali soil salinity and nitrate environmental risk cooperative control method. The saline-alkali soil salinity and nitrate environmental risk cooperative control method comprises the following steps that S1, lithium slag is added into saline-alkali soil before crops are planted, and maintenance is performed after rotary tillage and uniform mixing; s2, crops are planted in the saline-alkali soil, and calcium chloride waste liquid and nitrogen fertilizer are applied to the saline-alkali soil according to the conventional nitrogen application amount and fertilizer application habits of the crops. The method can achieve multiple purposes of reducing saline-alkali soil salinity, improving nitrogen utilization efficiency, controlling nitrogen fertilizer input, promoting normal growth of crops and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of saline-alkali land utilization, and particularly to a method for co-controlling salt content and nitrate environmental risk of saline-alkali land. BACKGROUND

[0002] The saline-alkali land is a general term of saline soil and alkaline soil. The saline soil mainly refers to a saline-alkali soil with high content of chlorides or sulfates, and the soil is alkaline. The alkaline soil refers to a soil with high content of carbonates or heavy phosphates, and the soil is alkaline. The saline-alkali land is prone to cause physiological drought and nutrient deficiency due to high salt content and ion toxicity, so that the crop yield is reduced or even cannot grow.

[0003] The fertilization principle of the saline-alkali soil is to mainly use organic fertilizer and high-efficiency compound fertilizer. The organic fertilizer is a carbon-containing material prepared by fermentation of resources rich in organic matter such as animal and plant residues and excrement, and contains a large amount of organic matter, which is beneficial to root growth and seedling promotion and buffers harmful anions and cations in the soil. The high-concentration compound fertilizer is a compound fertilizer with total nutrient content of more than 40 %, and has less invalid components and less residues. However, the fertilizer amount should not be too much at a time to avoid aggravating the secondary salinization of the soil. At present, there are still problems such as low fertilizer utilization efficiency and poor crop growth in the comprehensive utilization of the saline-alkali land.

[0004] In view of this, the present application is provided. SUMMARY

[0005] The present application aims to provide a method for co-controlling salt content and nitrate environmental risk of saline-alkali land, which can achieve multiple goals such as reducing soil salt content, improving nitrogen utilization efficiency, controlling nitrogen fertilizer input, and promoting normal growth of crops.

[0006] The present application provides a method for co-controlling salt content and nitrate environmental risk of saline-alkali land, comprising the following steps: S1: adding lithium residue to the saline-alkali land soil before planting crops, and mixing and maintaining after rotary tillage; S2: planting crops in the saline-alkali land soil, and applying calcium chloride waste liquid and nitrogen fertilizer to the saline-alkali land soil according to the conventional nitrogen application amount and fertilization habit of the crops.

[0007] In the present application, the salt content of the saline-alkali land is 0.1-0.6 %, and the pH value is 8.0-9.5.

[0008] Lithium residue is a waste discharged in the process of extracting lithium salt from spodumene, which is rich in SiO2 and Al2O3, has a large specific surface area and a porous structure, and has a strong adsorption performance. More specifically, the main components and mass content of the lithium residue are as follows: SiO2 35-50 %, Al2O3 18-25 %, and lithium oxide content 0.19-0.4 %; the main physicochemical parameters of the lithium residue are as follows: pH value 3.5-5.5, and specific surface area 3-6 m 2 / g.

[0009] Further, before adding the lithium residue, the lithium residue can be dried, ball milled, and sieved, wherein the drying temperature is 80-100 ℃, the drying time is 8-12 h, the ball milling time is 1-3 h, and the sieving is 100-200 mesh.

[0010] Further, before adding the lithium residue, the soil sample of the saline-alkali soil can be collected to determine the soil pH value, salt content, water-soluble chlorine content, nitrate nitrogen content, and the like, so as to control the relevant parameters of subsequent planting according to the determination results.

[0011] In the present application, the lithium residue can be added 20-40 days before planting crops; the addition amount of the lithium residue can be 0.2-0.6 % of the dry soil weight of the plough layer soil; and the curing time can be 10-20 days. Research shows that the lithium residue is acidic, rich in SiO2 and Al2O3, has a large specific surface area and a porous structure, and has a strong adsorption performance, which can effectively reduce the pH value and salt content of the saline-alkali soil.

[0012] In step S2, the planted crops are not strictly limited, and the crops can be, for example, wheat, corn, Chinese cabbage, tomato, and the like, various food crops, vegetables, and economic crops.

[0013] The total amount of chlorine and nitrogen is the conventional nitrogen amount of the crops, the final chlorine addition amount and nitrogen addition amount are calculated according to the chlorine-nitrogen molar ratio of 3:7 to 5:5, the final calcium chloride waste liquid application amount and nitrogen fertilizer application amount are converted, the chlorine-nitrogen molar ratio is, for example, 3:7, 4:6, 5:5, and the like; wherein the maximum concentration of chlorine in the saline-alkali soil is controlled to be not more than 300 mg / kg. In addition, the calcium chloride waste liquid and nitrogen fertilizer can be applied to the saline-alkali soil at the base fertilizer stage or at the base fertilizer and topdressing stages according to the crop fertilization habit.

[0014] In the present application, the calcium chloride waste liquid is a waste liquid discharged in the process of treating phosphate ore by hydrochloric acid method, which is rich in Ca 2+ and Cl - . More specifically, the calcium chloride content in the calcium chloride waste liquid is 20-30 %.

[0015] Further, before the calcium chloride waste liquid is applied, the calcium chloride waste liquid can be subjected to fluorine removal treatment; specifically, the fluorine removal treatment comprises adding a fluorine removal precipitant to the calcium chloride waste liquid, and adding a sodium salt or an aluminum salt as the fluorine removal precipitant, to generate a slightly water-soluble Na3AlF6 or calcium fluoride precipitate, so as to remove high fluorine in the calcium chloride waste liquid and control fluorine pollution.

[0016] The calcium chloride waste liquid is rich in Ca 2+ and Cl - , Ca 2+ can replace Na + and Mg 2+ adsorbed in soil colloids, so that the sodium ion hydrophilic colloids become calcium hydrophobic colloids, thereby improving soil structure and permeability and playing a role in desalination; Cl - has similar physical and osmotic regulation effects to NO3 - and shares a transport mechanism, Cl - is preferentially partitioned in plant vacuoles, so as to reduce the accumulation of NO3 - in the vacuoles, so that more NO3 - participates in the synthesis of organic nitrogen and biological compounds, thereby achieving higher nitrogen utilization efficiency; at the same time, when the nitrogen content in the environment is low, the inhibition of Cl - inflow is reduced, and the increase in Cl - content can replace NO3 - in cells to play an osmotic role, thereby further improving nitrogen utilization efficiency. Studies have shown that the combined use of lithium residue and calcium chloride waste liquid can achieve multiple goals of reducing soil salinity, improving nitrogen utilization efficiency, controlling nitrogen fertilizer input, and promoting normal growth of crops; at the same time, lithium residue and calcium chloride waste liquid are industrial waste resources, which are used after the above specific treatment, so as to realize the resource utilization of waste and not cause secondary pollution to the environment.

[0017] In addition, the application of nitrogen fertilizer to saline-alkali soil can effectively reduce the accumulation of Na + in crops, regulate K + / Na + balance, promote the synthesis of osmotic regulation substances such as amino acids, balance the redox system, and alleviate the reduction of photosynthetic capacity, thereby improving crop growth. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1The pH value of the soil after the end of planting in Example 1 was detected; Figure 2 The salt content of the soil after the end of planting in Example 1 was detected; Figure 3 The dry weight of the crop after the end of planting in Example 1 was detected; Figure 4 The nitrogen utilization efficiency result after the end of planting in Example 1 was detected; Figure 5 The planting map of the crop in Example 1. DETAILED DESCRIPTION

[0020] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0021] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form also includes the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations, devices, components and / or combinations thereof.

[0022] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0023] The lithium slag and calcium chloride waste liquid used in each embodiment are as follows: Lithium slag: SiO238 %, Al2O322 %, lithium oxide 0.21 %; pH value 4.1, specific surface area 4 m 2 / g.

[0024] Calcium chloride waste liquid: calcium chloride 25 %.

[0025] Example 1 I. Waste resources and pretreatment 1. Pretreatment of lithium slag The lithium slag was dried, ball milled and sieved; the drying temperature was 80 ℃, the drying time was 10 h; the ball milling time was 2 h; and the sieving was through a 100 mesh sieve.

[0026] 2. Pretreatment of calcium chloride waste liquid Fluorine is removed from the calcium chloride waste liquid by adding sodium and aluminum containing salts to the calcium chloride waste liquid to generate Na3AlF6 which is slightly soluble in water.

[0027] II. Salt and nitrate environmental risk synergistic control of saline-alkali soil Before planting crops, the soil sample of the saline-alkali soil without fertilization was collected to determine the soil pH value, salt content, water-soluble chlorine content, nitrate nitrogen content and other indicators; the results are as follows: pH is 8.9, salt content is 0.35 %, water-soluble chlorine content is 38 mg / kg, and nitrate nitrogen content is 25 mg / kg.

[0028] The pretreated lithium residue was added 30 days before planting crops, and the addition amount was 0.2 %, 0.4 % and 0.6 % of the dry soil weight of the plough layer, respectively, and the soil was mixed by rotary tillage and maintained for 2 weeks.

[0029] After maintenance, the crops were planted with cabbage, and the total amount of chlorine and nitrogen was the conventional nitrogen amount for crop fertilization, the final chlorine addition amount and nitrogen addition amount were calculated according to the chlorine-nitrogen molar ratio of 3:7, 4:6 and 5:5, respectively, the final calcium chloride waste liquid and nitrogen fertilizer application amount was converted, and the maximum concentration of chlorine in the soil was controlled to be not more than 300 mg / kg.

[0030] According to the crop fertilization habit and the above calculated amount, the pretreated calcium chloride waste liquid and nitrogen fertilizer were applied at the base fertilizer stage.

[0031] After the crops were planted, the soil and plant samples were collected, and the nitrogen, biomass and chlorine were determined; at the same time, no lithium residue and calcium chloride waste liquid were added as a blank control (CK), and the results are shown in Figures 1-5 .

[0032] The results show that after the planting of the embodiment is completed, the pH value of the soil is 7.82, the salt content is 0.20 %, the dry weight of the crops is 0.99 g / plant, and the nitrogen utilization efficiency is 68.5 %.

[0033] Example 2 I. Waste resources and pretreatment 1. Pretreatment of lithium residue The lithium residue was dried, ball milled and sieved; the drying temperature was 100 ℃, the drying time was 12 h, the ball milling time was 1.5 h, and the sieving was 200 mesh.

[0034] 2. Pretreatment of calcium chloride waste liquid Fluorine is removed from the calcium chloride waste liquid by adding calcium salt to the calcium chloride waste liquid to form calcium fluoride precipitate to remove fluorine from the calcium chloride waste liquid.

[0035] II. Salt and nitrate environmental risk synergistic control of saline-alkali soil Before planting crops, the soil sample of the unfertilized saline-alkali soil is collected to determine the indexes of soil pH, salt content, water-soluble chlorine content, nitrate nitrogen content, etc. The results are as follows: pH is 8.6, salt content is 0.25%, water-soluble chlorine content is 20 mg / kg, and nitrate nitrogen content is 18 mg / kg.

[0036] The pretreated lithium residue is added 20 days before planting crops, and the addition amount is 0.4% of the dry soil weight of the plough layer. After mixing by rotary tillage, it is maintained for 10 days.

[0037] After maintenance, corn is planted as crops. The total amount of chlorine and nitrogen is the conventional nitrogen application amount for crops. The final chlorine addition amount and nitrogen addition amount are calculated according to the chlorine-nitrogen molar ratio of 4:6. The final calcium chloride waste liquid and nitrogen fertilizer application amounts are converted, and the maximum concentration of chlorine in the soil is controlled to be no more than 300 mg / kg.

[0038] According to the crop fertilization habit and the above-mentioned calculated amount, the pretreated calcium chloride waste liquid and nitrogen fertilizer are applied at the base fertilizer stage.

[0039] After the end of crop planting, soil and plant samples are collected for nitrogen, biomass, and chlorine determination. The results show that after the end of planting in this example, the soil pH is 7.73, the salt content is 0.12%, the crop dry weight is 415.7 g / plant, and the nitrogen utilization efficiency is 60.1%.

[0040] Example 3 I. Waste resources and pretreatment 1. Pretreatment of lithium residue The lithium residue is dried, ball milled, and sieved. The drying temperature is 90°C, the drying time is 10h, the ball milling time is 3h, and the sieving is 100 mesh.

[0041] 2. Pretreatment of calcium chloride waste liquid Sodium and aluminum containing salts are added to the calcium chloride waste liquid to remove fluorine, generating Na3AlF6 which is slightly soluble in water, to remove fluorine from the calcium chloride waste liquid.

[0042] II. Salinity and nitrate environmental risk synergistic control of saline-alkali soil Before planting crops, the soil sample of the unfertilized saline-alkali soil is collected to determine the indexes of soil pH, salt content, water-soluble chlorine content, nitrate nitrogen content, etc. The results are as follows: pH is 9.2, salt content is 0.55%, water-soluble chlorine content is 75 mg / kg, and nitrate nitrogen content is 32 mg / kg.

[0043] The pretreated lithium residue is added 40 days before planting crops, and the addition amount is 0.6% of the dry soil weight of the plough layer. After mixing by rotary tillage, it is maintained for 20 days.

[0044] After the maintenance, the crop wheat is planted, the total amount of chlorine and nitrogen is added according to the conventional nitrogen application amount of the crop, the final chlorine addition amount and nitrogen addition amount are calculated according to the chlorine-nitrogen molar ratio of 5:5, the final calcium chloride waste liquid and nitrogen fertilizer application amounts are converted, and the highest concentration of chlorine in the soil is controlled to be not more than 300 mg / kg.

[0045] According to the crop fertilization habit and the calculated amount, the pretreated calcium chloride waste liquid and nitrogen fertilizer are applied at the base fertilizer stage.

[0046] After the crop planting is completed, the soil and plant samples are collected, and the nitrogen, biomass and chlorine are determined; the results show that after the planting of the embodiment is completed, the pH value of the soil is 8.43, the salt content is 0.28%, and the nitrogen utilization efficiency is 58.6%.

[0047] Comparative Example 1 Except that only lithium residue is not added, and the chlorine-nitrogen molar ratio is 4:6, the rest is the same as Example 1.

[0048] The results show that after the planting of the comparative example is completed, the pH value of the soil is 8.8, the salt content is 0.36%, the dry weight of the crop is 0.52 g / plant, and the nitrogen utilization efficiency is 45.3%.

[0049] Comparative Example 2 Except that only calcium chloride waste liquid is not added, and the lithium residue addition amount is 0.4% of the dry soil weight of the plough layer, the rest is the same as Example 1.

[0050] The results show that after the planting of the comparative example is completed, the pH value of the soil is 8.02, the salt content is 0.26%, the dry weight of the crop is 0.59 g / plant, and the nitrogen utilization efficiency is 42.3%.

[0051] Comparative Example 3 Except that coal gangue is used to replace the lithium residue of Example 1 (the addition amount is 0.4% of the dry soil weight of the plough layer), and the chlorine-nitrogen molar ratio is 4:6, the rest is the same as Example 1.

[0052] The results show that after the planting of the comparative example is completed, the pH value of the soil is 8.42, the salt content is 0.30%, the dry weight of the crop is 0.61 g / plant, and the nitrogen utilization efficiency is 46.9%.

[0053] Comparative Example 4 Except that fly ash is used to replace the lithium residue of Example 1 (the addition amount is 0.4% of the dry soil weight of the plough layer), and the chlorine-nitrogen molar ratio is 4:6, the rest is the same as Example 1.

[0054] The results showed that the pH value of soil was 8.22, the salt content was 0.29%, the dry weight of crop was 0.63 g / plant, and the nitrogen use efficiency was 50.5% after the cultivation of the control example.

[0055] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for synergistic control of environmental risks from salinity and nitrate in saline-alkali land, characterized in that, Includes the following steps: S1: Add lithium slag to saline-alkali soil before planting crops, mix it thoroughly by rotary tillage, and then maintain it. S2: When planting crops in saline-alkali soil, calcium chloride waste liquid and nitrogen fertilizer are applied to the saline-alkali soil according to the conventional nitrogen application rate and fertilization habits of the crops.

2. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, Add lithium slag 20-40 days before planting crops.

3. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, The amount of lithium slag added is 0.2-0.6% of the dry soil mass of the topsoil.

4. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, The maintenance period is 10-20 days.

5. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, When applying calcium chloride waste liquid and nitrogen fertilizer, control the chlorine-nitrogen molar ratio to be 3:7 to 5:

5.

6. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, After applying calcium chloride waste liquid in step S2, the maximum concentration of chlorine in the saline-alkali soil is controlled to not exceed 300 mg / kg.

7. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, The application of calcium chloride waste liquid and nitrogen fertilizer to saline-alkali soil according to the conventional nitrogen application rate and fertilization habits of crops in step S2 refers to applying calcium chloride waste liquid and nitrogen fertilizer to saline-alkali soil at the basal fertilizer stage or at the basal fertilizer and topdressing stages respectively.

8. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, Before adding lithium slag, the lithium slag should be dried, ball-milled, and sieved.

9. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, The lithium slag contains 35-50% SiO2, 18-25% Al2O3, and 0.19-0.4% lithium oxide.

10. The method for synergistic control of salinity and nitrate environmental risks in saline-alkali land according to claim 1, characterized in that, The calcium chloride content in the calcium chloride waste liquid is 22-30%.

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