Fertilizing method for reducing heavy metal on surface layer of rice soil based on multi-source organic fertilizer

Abstract

The invention belongs to the technical field of agricultural planting, and particularly discloses a fertilization method for reducing heavy metals on the surface layer of rice soil based on a multi-source organic fertilizer. The fertilization treatment method provided by the invention comprises six treatments of astragalus sinicus (T1), astragalus sinicus + pig manure late rice (T2), astragalus sinicus + pig manure late rice + straw winter cover (T3), astragalus sinicus + straw winter cover (T4), NPK (T5) and a blank control group. According to different fertilization methods such as application of organic fertilizer, the content of Cu, Cr and Zn elements in surface soil of the paddy field can be reduced by a treatment mode of using astragalus sinicus 1500 and pig manure late rice, and the content of heavy metal elements such as Co, As, Sn, Ni, Pb, Cr and Cu can be increased by a fertilization mode of adding straw winter cover. According to the method, in the fertilization treatment of the paddy field, a treatment mode of milk vetch 1500 + pig manure late rice should be selected, and a fertilization mode of adding straw winter covers is avoided, so that the purpose of reducing the content of heavy metal elements is achieved, and the method has wide applicability for improving the rice yield.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural planting, and in particular relates to a fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizers. Background Art

[0002] Heavy metals in soil come from a wide range of sources, which can be roughly divided into natural input and anthropogenic input. Weathering of soil parent material, as the main natural source of heavy metals in soil, largely determines the background value of heavy metals in soil. The source of anthropogenic activities is more complicated, mainly including the accumulation of solid waste, irrational application of fertilizers and pesticides, sewage irrigation, etc. In recent years, with the rapid development of industrial-grade urbanization, the rate of anthropogenic input of heavy metals in soil has far exceeded the natural accumulation rate of heavy metals. Traffic and industrial emissions are the main sources of heavy metals in urban soil. Heavy metals in mining soil mainly come from the accumulation of sulfur-containing tailings, mine waste rock, smelting slag, etc. in the open air. These solid wastes can produce corrosive acid mine drainage (AMD). This type of wastewater is extremely acidic (pH <3) and contains high concentrations of heavy metal ions such as Zn, Cd, Cu, and Pb. It will penetrate into the soil and water and cause serious heavy metal pollution. The irrational application of fertilizers and pesticides during agricultural production will lead to the accumulation of heavy metals in farmland soil. Some inorganic fertilizers, especially phosphate fertilizers, often contain high concentrations of heavy metals. Long-term application of such fertilizers will lead to rapid accumulation of heavy metals in farmland soil, which will also harm the environment and human health through the food chain. The applied pesticides will also flow into the soil under the scouring of rainwater, causing a certain degree of load on the farmland soil.

[0003] In 2011, a survey of 2.373 million mu of rice fields in 88 counties and districts in key pollution areas in Hunan, Hubei, Sichuan and Jiangxi provinces showed that 67.8% of the soil exceeded the relevant indicators of heavy metals in agricultural land. In addition, the 2014 National Soil Status Survey Bulletin showed that the rate of excessive heavy metals in soil nationwide (excluding Hong Kong, Macao and Taiwan) was as high as 16.1%, among which the rate of excessive Cd pollution ranked first among all the heavy metals investigated (Cd, Hg, As, Cu, Pb, Cr, Zn, Ni), which seriously affected agricultural production in areas where soil exceeded the standard and the health of residents. Therefore, my country's soil heavy metal pollution needs to be improved and resolved urgently, and soil Cd pollution is the top priority of pollution control.

[0004] Therefore, studying the effects of different fertilization treatments on the content and morphological distribution of heavy metal elements in the soil has important scientific significance and social value. The correct fertilization method can improve soil fertility quality and agricultural production capacity and reduce the content of heavy metals in the soil. This patent aims to explore the effects of different fertilization treatments on the content of heavy metal elements in the surface soil of rice fields. By comparing the changes in the content of heavy metal elements in the soil under different fertilization treatments, a scientific basis is provided for further increasing rice yields, ensuring the quality of agricultural products and environmental safety.

[0005] Technical Solution

[0006] To solve the above problems, the present invention adopts the following technical solutions.

[0007] A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizers comprises the following steps:

[0008] (1) Determine the research area and sampling site, and collect surface soil samples from rice fields;

[0009] (2) Determine the heavy metal content of topsoil samples from rice fields with six different fertilization treatments;

[0010] (3) To explore the effects of different fertilization treatments on the content of heavy metal elements in the surface soil.

[0011] The above-mentioned fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer,

[0012] Step (1) The method for sampling the topsoil of rice fields is based on the "Guidelines for Soil Quality Soil Sampling Technology"

[0013] (GB / T36197) is used to collect soil samples required for the experiment.

[0014] The above-mentioned fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer,

[0015] The water used in step (2) should be high-purity water with a resistivity of 18.2 MΩ, the acid used should be high-grade pure GR or higher-purity acid purified by two sub-boiling distillations, and the container used should be a polytetrafluoroethylene digestion tube, which has been cleaned with 10% by mass of high-grade pure nitric acid;

[0016] This step should be performed in a clean laboratory of Class 1000 or higher.

[0017] The above-mentioned fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer,

[0018] The sample digestion process in step (2) is:

[0019] First, add hydrogen peroxide for digestion. After evaporation, add a mixture of concentrated nitric acid and hydrogen peroxide and heat for further digestion. After evaporation, add a mixture of concentrated nitric acid and concentrated hydrochloric acid for digestion until the solution is clear. Finally, evaporate to dryness and dissolve in dilute nitric acid.

[0020] The above-mentioned fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer,

[0021] After the digestion in step (2) is completed, the heavy element content in the soil surface layer is determined using an inductively coupled plasma mass spectrometer ICP-MS.

[0022] The above-mentioned fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer,

[0023] The different fertilization methods in step (3) include: Astragalus sinicus as a natural green manure, by collecting the cultivated Astragalus sinicus and drying it in the sun, then chopping the dried Astragalus sinicus into small pieces and mixing them into compost or soil to improve soil fertility. Astragalus sinicus 1500 refers to applying 1500 kg per mu to the experimental plot. Pig manure late rice refers to returning 300 kg per mu of rice straw (late rice) from the previous season to the experimental plot. Rice straw winter cover is an agricultural production technology that refers to the use of discarded rice straw and stalks and other materials after the autumn harvest to cover the fields to maintain the temperature and humidity of the fields. NPK is a nitrogen, phosphorus and potassium compound fertilizer applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the content of Co, As and Sn in the surface soil under different fertilization methods;

[0025] Figure 2 is the content of Ni, Cu and Pb in the surface soil under different fertilization methods;

[0026] Figure 3 is the content of Cr, Mn and Zn in the surface soil under different fertilization methods. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific embodiments.

[0028] The implementation of this method is divided into the following steps:

[0029] Step 1: Determine the research area and sampling location, and collect surface soil samples from rice fields.

[0030] The sample collection operation in this step shall be based on the Technical Guidelines for Soil Sampling of Soil Quality (GB / T36197).

[0031] The purpose of this step is to obtain as much information as possible about the research area and sampling sites, and collect the required samples according to the research object. This step is implemented in accordance with the national standard and is not an innovative content of this method.

[0032] Step 2: Determine the heavy metal content of topsoil samples from rice fields with six different fertilization treatments.

[0033] The water used in this step should be high-purity water with a resistivity of 18.2 MΩ, the acid used should be high-grade pure GR or higher-purity acid purified by two sub-boiling distillations, and the container used should be a polytetrafluoroethylene digestion tube, which should be cleaned with 10% mass fraction of high-grade pure nitric acid.

[0034] The sample digestion process recommended by this method is:

[0035] Weigh 25.0 mg of sample and place it in a 7 ml beaker. Add 300 μl H2O2 to the weighed soil sample, shake well and evaporate to dryness with the lid open. The initial temperature is 70°C, which can be raised to 95°C after 15 minutes. After most of it is dry, it can be raised to 110 or 120°C. After evaporation, add 200 μl H2O2 and 400 μl concentrated HNO3, tighten the lid and place it at room temperature for 20 minutes (no heating), then open the lid and evaporate to dryness, the temperature is the same as above. Observation steps: If there is black insoluble matter in the sample after evaporation, add 750 μl concentrated HCl + 250 μl concentrated HNO3, place it on the hot plate with the lid half-covered and evaporate to dryness at 90°C. If there is no black insoluble matter in the sample after evaporation, add 600 ul concentrated HF + 300 μl concentrated HNO3 to dissolve the silicate substance, tighten the lid and place it on the hot plate at 100°C overnight, and evaporate to dryness with the lid open at 95°C. After the sample is evaporated to dryness, add 400μl 6N·HCl and heat on a hot plate at 100℃ for 20min to observe whether the solution is clear; if there is still white flocculent precipitate, continue to add 500 or 1000μL (add 500μL when the sample amount is <5mg, add 1000μL when >5mg) 6N·HCl to remove insoluble fluoride, and evaporate to dryness at 100℃ with the lid open.

[0036] After the sample digestion is completed, the heavy metal content is determined by inductively coupled plasma mass spectrometry (ICP-MS). In actual operation, the digestion steps can be appropriately increased or decreased according to the properties of the sample.

[0037] The purpose of this step is to obtain the heavy metal content in the soil sample. The benefits of reagent selection, purification and operation in a clean laboratory in this step are to reduce the background value of the whole process and reduce experimental errors. The benefit of selecting an inductively coupled plasma mass spectrometer to determine the element content in this step is to improve the test accuracy.

[0038] Step three, explore the effects of different fertilization treatments on the content of heavy metal elements in the surface soil.

[0039] Example 1

[0040] The content of heavy metal elements in the topsoil of rice fields under different fertilization treatments is in the following order from high to low:

[0041] Co:CK>Astragalus 1500+Straw Winter Cover>NPK>Astragalus 1500>Astragalus 1500+Pig Manure Late Rice+Straw Winter Cover>Astragalus 1500+Pig Manure Late Rice

[0042] As: Astragalus 1500+rice straw winter cover>CK>NPK>Astragalus 1500>Astragalus 1500+pig manure late rice+rice straw winter cover>Astragalus 1500+pig manure late rice

[0043] Sn: Astragalus 1500+rice straw winter cover>CK>NPK>Astragalus 1500+pig manure late rice+rice straw winter cover>Astragalus 1500>Astragalus 1500+pig manure late rice

[0044] The experimental results show that the fertilization method of Astragalus 1500 + rice straw winter cover for the three heavy metal elements Co, As and Sn will increase the concentration of the elements, while the content of these three heavy elements is the lowest when using Astragalus 1500 + pig manure late rice fertilization method. At the same time, adding rice straw winter cover on the basis of Astragalus 1500 + pig manure late rice will lead to an increase in the content of these three heavy metals in the topsoil. Among them, the Co element, after using other fertilization methods, has reduced the content of this element in the topsoil of rice fields. It can be seen that adding Astragalus 1500 to fertilize the soil can reduce the content of Co, As and Sn heavy metal elements in the topsoil of rice fields. When fertilized at the same time as pig manure late rice, the content of these three heavy metal elements in the topsoil is lower. Under other equal conditions, the content of heavy metal elements in the fertilization treatment method of adding rice straw winter cover increases significantly, so the fertilization method of rice straw winter cover is not recommended.

[0045] Example 2

[0046] The content of heavy metal elements in the topsoil of rice fields under different fertilization treatments is in the following order from high to low:

[0047] Ni: Astragalus 1500+rice straw winter cover>Astragalus 1500+pig manure late rice+rice straw winter cover>NPK>CK>Astragalus 1500>Astragalus 1500+pig manure late rice

[0048] Cu: Astragalus sinicus 1500+pig manure late rice+rice straw winter cover>Astragalus sinicus 1500+pig manure late rice>Astragalus sinicus 1500+rice straw winter cover>CK>Astragalus sinicus 1500>NPK

[0049] Pb: Astragalus 1500>CK>Astragalus 1500+rice straw winter cover>Astragalus 1500+pig manure late rice+rice straw winter cover>Astragalus 1500+pig manure late rice>NPK

[0050] As shown in the figure, different fertilization treatments have limited effects on the content of two heavy metal elements, Ni and Pb, in the topsoil of rice fields, while the content of Cu in the topsoil increased significantly when Chinese Astragalus 1500+pig manure late rice+rice straw winter cover and Chinese Astragalus 1500+pig manure late rice were fertilized, which was twice the content of other fertilization treatments. It can be concluded that rice straw winter cover will lead to an increase in the content of heavy metal elements Cu, Ni, and Pb in the topsoil of rice fields.

[0051] Example 3

[0052] The content of heavy metal elements in the topsoil of rice fields in Jinxian County under different fertilization treatments is in the following order from large to small:

[0053] Cr: Astragalus 1500+rice straw winter cover>Astragalus 1500+pig manure late rice+rice straw winter cover>NPK>Astragalus 1500>CK>Astragalus 1500+pig manure late rice

[0054] Mn:CK>NPK>Astragalus sinicus 1500+pig manure late rice+rice straw winter cover>Astragalus sinicus 1500+rice straw winter cover>Astragalus sinicus 1500>Astragalus sinicus 1500+pig manure late rice

[0055] Zn: Astragalus sinicus 1500+pig manure late rice+rice straw winter cover>Astragalus sinicus 1500+pig manure late rice>Astragalus sinicus 1500+rice straw winter cover>NPK>Astragalus sinicus 1500>CK

[0056] The figure shows that the Cr and Zn elements have higher content in the two fertilization treatments of Astragalus 1500 + pig manure late rice and Astragalus 1500 + pig manure late rice + rice straw winter cover, while the element content of only Astragalus 1500 and Astragalus 1500 + rice straw winter cover is relatively low. The content of elements in the fertilization treatments of other methods did not change much. However, the content of Mn element decreased slightly after being treated with other fertilization methods. It can be concluded that when the fertilization treatment method is Astragalus 1500 + pig manure late rice, adding rice straw winter cover on this basis will lead to an increase in the content of heavy metal elements. Therefore, rice straw winter cover will increase the content of Cr, Zn, and Mn elements in the topsoil of rice fields.

[0057] According to the experimental results of this patent, the present invention should select the treatment method of Chinese Astragalus 1500+pig manure late rice in the fertilization treatment of paddy fields to reduce the content of heavy metal elements in the topsoil of paddy fields. At the same time, the fertilization method with rice straw winter cover should be avoided, because this method will lead to an increase in the content of heavy metal elements. For the content of two heavy metal elements Ni and Pb, the influence of different fertilization treatment methods is not large, so any fertilization method can be selected for fertilization treatment. However, for the content of Cu, Cr and Zn elements, the treatment methods of Chinese Astragalus 1500+pig manure late rice+rice straw winter cover and Chinese Astragalus 1500+pig manure late rice should be avoided to avoid the increase in the content of these heavy metal elements. For the content of heavy metal elements such as V, Ce, Nd, Sr, different fertilization treatment methods have little effect on the content in the topsoil of paddy fields, but the treatment method of Chinese Astragalus 1500+pig manure late rice can reduce the content of heavy metal elements. Therefore, when choosing a fertilization method, the effects on all heavy metal elements should be taken into consideration to achieve the best fertilization effect.

[0058] It can be seen from the above implementation cases that in the fertilization treatment of paddy fields, the treatment method of Chinese Astragalus 1500 + pig manure late rice should be selected, and the fertilization method with rice straw winter cover should be avoided to achieve the purpose of reducing the content of heavy metal elements. The fertilization method of the present invention can effectively regulate the content of heavy metal elements in rice plants, improve rice yield and quality, and has good application prospects. The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizers, characterized in that: Different experimental plots were divided on the red soil of the experimental base, and six different fertilization treatments were used in the plots. CK is the control without fertilizer, Chinese milk vetch 1500 is 1500 kg of Chinese milk vetch per mu of land, pig manure late rice is 300 kg of rice straw from the previous season returned to the field per mu, winter cover rice straw is also 300 kg per mu, and NPK is the application of chemical fertilizers.

2. A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer according to claim 1, characterized in that: The sampling standard for surface soil samples shall be based on the Technical Guidelines for Soil Sampling of Soil Quality (GB / T36197), and the soil samples required for the experiment shall be collected.

3. A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer according to claim 1, characterized in that: The water used in the digestion process of surface soil samples should be high-purity water with a resistivity of 18.2MΩ, the acid used should be high-grade pure GR or higher-purity acid purified by two sub-boiling distillations, and the container used should be a polytetrafluoroethylene digestion tube, which should be cleaned with 10% mass fraction of high-grade pure nitric acid; The digestion process should be carried out in a clean laboratory of Class 1000 or higher.

4. A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer according to claim 3, characterized in that: The digestion process of surface soil samples is as follows: First, add hydrogen peroxide for digestion. After evaporation, add a mixture of concentrated nitric acid and hydrogen peroxide and heat for further digestion. After evaporation, add a mixture of concentrated nitric acid and concentrated hydrochloric acid for digestion until the solution is clear. Finally, evaporate to dryness and dissolve in dilute nitric acid.

5. A fertilization method for reducing heavy metals in the surface layer of paddy soil based on multi-source organic fertilizer according to claim 4, characterized in that: After digestion, the content of heavy metal elements was determined by inductively coupled plasma mass spectrometry (ICP-MS).

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