Method for synergistically treating cadmium-polluted soil by using green manure and wollastonite

Abstract

The invention relates to the technical field of heavy metal treatment. The invention provides a method for synergistically treating cadmium-polluted soil by using green manure and wollastonite. The method comprises the following steps: (1) interplanting green manure crops before harvesting rice; (2) after the rice is harvested, ditching in the field; (3) applying wollastonite before rice transplanting, and returning the wollastonite and green manure crops to the field; (4) irrigating the field for field retting; (5) applying a base fertilizer after field retting, and inserting seedlings; and (6) topdressing in the tillering stage of the rice. Green manure is returned to the field, so that the soil fertility is improved, and the rice growth is promoted. Wollastonite is used for providing a silicon fertilizer for growth and development of rice, and meanwhile, the bioavailability of soil cadmium is reduced. The green manure and the wollastonite cooperate with each other, so that the content of effective cadmium in the soil and the content of cadmium in the brown rice are efficiently reduced, and the green manure and the wollastonite are cooperatively applied to the rice field soil and can play a greater role in cadmium control.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal treatment, and in particular to a method for synergistically treating cadmium-contaminated soil by utilizing green manure and wollastonite. Background Art

[0002] Heavy metal cadmium (Cd) has the characteristics of long decomposition cycle, high mobility, high toxicity, strong concealment, irreversibility, and difficulty in degradation. It is one of the "five poisons" of heavy metals. With the extensive development of the economy and society, agricultural production, industrial and mining and other human activities, as well as high natural background values, the problem of soil heavy metal Cd pollution and excessive standards has become increasingly prominent. Cd is easily absorbed by rice, causing a significant reduction in rice production and quality, endangering human health, and causing cancer and other diseases. In recent years, the phenomenon of excessive cadmium in paddy field soil has been serious. Farmland has been used more than maintained, and the treatment of cadmium-contaminated soil has only focused on restoration, while ignoring the endogenous regulatory function of the soil, thereby aggravating soil degradation. It is crucial to seek ways to efficiently treat soil cadmium pollution and simultaneously cultivate fertilizers.

[0003] Planting and utilizing green manure is an efficient means to improve soil fertility and crop yields. It can also be used as a biological passivation material to alleviate soil Cd pollution. However, its remediation effect is limited. Wollastonite can not only supplement the indispensable silicon fertilizer for rice growth and development, but is also a cadmium passivation material with significant results in the treatment of Cd-contaminated soil. The synergy of the two can give full play to the Cd pollution remediation effect and ensure the cadmium-compliant production of rice. Summary of the invention

[0004] The purpose of the present invention is to provide a method for synergistically treating cadmium-contaminated soil by utilizing green manure and wollastonite, so as to synergistically reduce the content of effective cadmium in the soil and the content of cadmium in brown rice.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for synergistically treating cadmium-contaminated soil by utilizing green manure and wollastonite, comprising the following steps: (1) Interplanting green manure crops before rice harvest; (2) After rice is harvested, dig trenches in the fields; (3) Apply wollastonite before rice transplanting and return the wollastonite and green manure crops to the field; (4) Irrigating the fields to make them retting; (5) After the soil is fermented, apply basal fertilizer and plant the seedlings; (6) Apply top dressing during the rice tillering stage.

[0006] Preferably, the type of green manure crop in step (1) is Chinese astragalus, and the variety of Chinese astragalus is Xiangzi No. 1.

[0007] Preferably, the interseeding in step (1) is performed 7 to 10 days before the rice matures, the sowing rate of the green manure crop is 1.5 to 2.0 kg / mu, and during the interseeding, the water on the surface of the rice field is drained and the rice is sown at the bottom.

[0008] Preferably, the method of digging trenches in step (2) is as follows: digging trenches around the field at the edge of the field, and digging crisscross trenches inside the field, wherein the width of the trenches is 15-25 cm, the depth is 15-25 cm, the spacing between the crisscross trenches is 5-8 m, and the trenches are connected to drainage outlets.

[0009] Preferably, the wollastonite in step (3) is spread on the surface of the field, and the amount of wollastonite applied is 180-220 kg / mu.

[0010] Preferably, the soil is returned to the field by turning over and pressing the soil, and the depth of the turning over and pressing is 15 to 20 cm.

[0011] Preferably, the retting in step (4) is carried out 5 to 10 days after the field return treatment, and the thickness of the water layer on the field surface during the retting is 1 to 2 cm.

[0012] Preferably, the base fertilizer in step (5) is applied 3 to 5 days after the soil is fermented.

[0013] Preferably, the variety of the rice seedlings in step (5) is Xiangzaoxian 45.

[0014] Preferably, the ratio of the base fertilizer in step (5) to the topdressing in step (6) is 3-5:5-7.

[0015] The present invention provides a method for synergistically treating cadmium-contaminated soil by utilizing green manure and wollastonite, comprising the following steps: (1) interplanting green manure crops before rice is harvested; (2) digging furrows in the field after rice is harvested; (3) applying wollastonite before rice is transplanted, and returning the wollastonite and green manure crops to the field together; (4) irrigating the field for fermentation; (5) applying base fertilizer after fermentation, and transplanting rice seedlings; and (6) applying topdressing during the tillering period of rice.

[0016] Beneficial effects of the present invention:

[0017] In order to solve the problem of excessive cadmium in rice under the rice-green manure crop rotation system, the material wollastonite is applied on the basis of the agricultural practice of turning green manure into fields to reduce the effectiveness of soil cadmium and the amount of cadmium absorbed by rice. The present invention innovatively combines the green manure turning technology and the wollastonite spreading technology into a set of technical models for repairing paddy field soil with moderate to mild cadmium pollution and reducing the cadmium content of brown rice.

[0018] The technical verification method is a field plot test, and the test results are generally consistent and representative. Based on the method in the invention, efficient cadmium control and rice cadmium compliance production under the rice-green manure crop rotation system can be achieved. The technology is simple, practical, and easy for farmers to operate and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Effects of different experimental treatments on soil available Cd content. Different lowercase letters above the columns represent significant differences among treatments, n=4, the same below.

[0020] Figure 2 Effects of different experimental treatments on the Cd content of brown rice, where P < 0.05 represents significant differences among the treatments at the P < 0.05 level, n=4, the same below.

[0021] Figure 3 Effects of different experimental treatments on Cd content in rice straw.

[0022] Figure 4 Effects of different experimental treatments on Cd content in rice roots. DETAILED DESCRIPTION

[0023] The present invention provides a method for synergistically treating cadmium-contaminated soil by utilizing green manure and wollastonite, comprising the following steps: (1) Interplanting green manure crops before rice harvest; (2) After rice is harvested, dig trenches in the fields; (3) Apply wollastonite before rice transplanting and return the wollastonite and green manure crops to the field; (4) Irrigating the fields to make them retting; (5) After the soil is fermented, apply basal fertilizer and plant the seedlings; (6) Apply top dressing during the rice tillering stage.

[0024] In the present invention, the type of green manure crop in step (1) is preferably Chinese astragalus, and the variety of Chinese astragalus is preferably Xiangzi No. 1.

[0025] In the present invention, the interseeding time in step (1) is preferably 7 to 10 days before rice maturity, more preferably 8 to 9 days, the sowing rate of the green manure crop is preferably 1.5 to 2.0 kg / mu, more preferably 1.7 to 1.8 kg / mu, and during the interseeding, the water on the surface of the rice field is drained and the rice is sown at the bottom.

[0026] In the present invention, the method of digging trenches in step (2) is preferably: digging trenches around the field at the edge of the field, and digging crisscross trenches inside the field. The width of the trenches is preferably 15-25 cm, more preferably 20 cm, and the depth is preferably 15-25 cm, more preferably 20 cm. The spacing of the crisscross trenches is preferably 5-8 m, more preferably 6-7 m, and the trenches are preferably connected to a drainage outlet.

[0027] In the present invention, the wollastonite in step (3) is preferably spread on the surface of the field when applied, and the application amount of the wollastonite is preferably 180-220 kg / mu, and more preferably 200 kg / mu.

[0028] In the present invention, the soil is preferably returned to the field by turning over and pressing in step (3), and the depth of the turning over and pressing is preferably 15 to 20 cm, and more preferably 17 to 18 cm.

[0029] In the present invention, the retting in step (4) is preferably carried out 5 to 10 days after the field return treatment, and more preferably 7 to 8 days. The thickness of the water layer on the field surface during the retting is preferably 1 to 2 cm, and more preferably 1.5 cm.

[0030] In the present invention, the base fertilizer in step (5) is preferably applied 3 to 5 days after retting, and more preferably 4 days.

[0031] In the present invention, the variety of the rice seedlings in step (5) is preferably Xiangzaoxian 45.

[0032] In the present invention, the ratio of the base fertilizer in step (5) to the topdressing in step (6) is preferably 3-5:5-7, and more preferably 4:6.

[0033] 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.

[0034] The wollastonite used in the embodiments and test examples of the present invention has a Ca content of 31.0% and a Si content of 0.02%. The remaining reagents can be purchased through commercial channels unless otherwise specified.

[0035] Example 1

[0036] A method for synergistically treating cadmium-contaminated soil by using green manure and wollastonite comprises the following steps: (1) Drain the water from the surface of the rice field 7 days before rice harvest and sow Xiangzi No. 1 astragalus seeds at the bottom of the rice field at a rate of 1.5 kg / mu; (2) After the rice is harvested, ditches are dug around the edge of the field and inside the field. The width of the ditches is 25 cm, the depth is 15 cm, the interval between the ditches is 8 m, and the ditches are connected to the drainage outlet; (3) Before transplanting rice seedlings, spread wollastonite on the surface of the field at a rate of 180 kg / mu, and turn over and return the wollastonite and astragalus to a depth of 20 cm; (4) 10 days after the return treatment, water the field until the water layer thickness on the field surface reaches 1 cm, and then retting the field; (5) After 5 days of retting, apply 30% of the annual fertilizer as base fertilizer, and then plant the seedlings of Xiangzaoxian No. 45; (6) During the tillering stage of rice, apply 70% of the annual fertilizer as top dressing.

[0037] Example 2

[0038] A method for synergistically treating cadmium-contaminated soil by using green manure and wollastonite comprises the following steps: (1) Drain the water from the surface of the rice field 10 days before rice harvest and sow Xiangzi No. 1 astragalus seeds at the bottom of the rice field at a rate of 2.0 kg / mu; (2) After the rice is harvested, ditches are dug around the edge of the field and inside the field. The width of the ditches is 15 cm, the depth is 25 cm, the interval between the ditches is 5 m, and the ditches are connected to the drainage outlet; (3) Before transplanting rice seedlings, spread wollastonite on the surface of the field at a standard of 220 kg / mu, and turn over and return the wollastonite and astragalus to a depth of 15 cm; (4) Five days after the treatment, water the field until the water layer thickness on the field surface reaches 2 cm, and then retting the field; (5) After 3 days of retting, apply 50% of the annual fertilizer as base fertilizer, and then plant the seedlings of Xiangzaoxian No. 45; (6) During the tillering stage of rice, apply 50% of the annual fertilizer as top dressing.

[0039] Example 3

[0040] A method for synergistically treating cadmium-contaminated soil by using green manure and wollastonite comprises the following steps: (1) Drain the water from the surface of the rice field 8 days before rice harvest and sow Xiangzi No. 1 astragalus seeds at the bottom of the rice field at a rate of 1.8 kg / mu; (2) After the rice is harvested, ditches are dug around the edge of the field and inside the field. The width and depth of the ditches are 20 cm and 20 cm, respectively. The interval between the ditches is 7 m and the ditches are connected to the drainage outlet. (3) Before transplanting rice seedlings, spread wollastonite on the surface of the field at a rate of 200 kg / mu, and turn over and return the wollastonite and astragalus to a depth of 17 cm; (4) Seven days after the return treatment, water the field until the water layer thickness on the field surface reaches 2 cm, and then retting the field; (5) After 4 days of retting, apply 40% of the annual fertilizer as base fertilizer, and then plant the seedlings of Xiangzaoxian No. 45; (6) During the tillering stage of rice, apply 60% of the annual fertilizer as top dressing.

[0041] Test example: Field plot test

[0042] 1. Experimental group design Winter fallow control treatment (CK): In this treatment, no green manure Chinese milk vetch was planted in the field, and 4 replications were set.

[0043] Green manure pressing and returning to the field treatment (MV): Green manure was interplanted before rice harvest and pressed in situ 10 days before rice transplanting the following year, with 4 replicates.

[0044] Wollastonite treatment (Si): No green manure was planted. Wollastonite powder was applied 10 days before rice transplanting at a dosage of 200 kg / mu, with 4 replicates.

[0045] Green manure turning and returning to the field + wollastonite treatment (MVSi): Green manure was interplanted before rice harvest, and the green manure was turned and pressed in situ 10 days before rice transplanting the following year. Wollastonite powder was applied at a dosage of 200 kg / mu, with 4 replicates.

[0046] Goethite treatment (Fe): No green manure was planted. Wollastonite powder was applied 10 days before rice transplanting at a dosage of 200 kg / mu, with 4 replicates.

[0047] Green manure turning and returning to the field + goethite treatment (MVFe): Green manure was interplanted before rice harvest, and the green manure was turned and pressed in situ 10 days before rice transplanting the following year. Goethite was applied at the same time, with a dosage of 200 kg / mu, and 4 repetitions were set.

[0048] Selenium mineral powder treatment (Se): No green manure was planted. Selenium mineral powder was spread 10 days before rice transplanting at a dosage of 200 kg / mu, with 4 replicates.

[0049] Green manure pressing and returning to the field + selenium mineral powder treatment (MVSe): Green manure was interplanted before rice harvest, and green manure was pressed in situ 10 days before rice transplanting the following year. Selenium mineral powder was applied at the same time, with a dosage of 200 kg / mu, and 4 replicates were set.

[0050] The remaining conditions were carried out according to the scheme of Example 3.

[0051] 2. The field experiment was carried out in cadmium-contaminated rice fields in Yiyang City, Hunan Province. The total cadmium content in the soil of the experimental field was 0.94 mg / kg, and the pH value was 6.40, which was a field with moderate to light cadmium pollution. Winter fallow control (CK), green manure turning and returning to the field (MV), wollastonite (Si), green manure turning and returning to the field + wollastonite (MVSi), goethite (Fe), green manure turning and returning to the field + goethite (MVFe), selenium ore powder (Se), green manure turning and returning to the field + selenium ore powder treatment (MVSe) were set. The dosage of goethite and selenium ore powder used as the comparison materials was the same as that of wollastonite, and the soil effective cadmium and cadmium content in different parts of rice (brown rice, straw and roots) during the rice harvest period of the year were analyzed and determined.

[0052] according to Figure 1 It can be seen that compared with the CK, MV, Si, MVFe and MVSe treatments, the effective cadmium content in the soil of the MVSi treatment was significantly reduced (P < 0.05), by 68.8%, 61.5%, 44.2%, 61.1% and 61.5%, respectively. Figure 2 It can be seen that the cadmium content of brown rice under the MVSi treatment was only 0.10 mg / kg, lower than the national safety standard cadmium pollution limit (0.20 mg / kg), achieving standard production. Compared with the MV, Si, MVFe and MVSe treatments, the cadmium content was significantly reduced by 76.4%, 55.6%, 67.7% and 66.7% respectively (P < 0.05). Figure 3 It can be seen that the cadmium content in rice straw treated with MVSi was the lowest, which was significantly reduced by 64.7%, 63.1%, 59.4% and 69.7% compared with the CK, MV, MVFe and MVSe treatments, respectively (P < 0.05). Figure 4 It can be seen that the cadmium content in the roots of rice in the MVSi treatment was significantly lower than that in the CK, MV, Si, MVFe and MVSe treatments (P < 0.05), with a decrease of 63.7%, 57.9%, 42.9%, 42.2% and 53.9%, respectively. In summary, green manure turning and returning to the field combined with wollastonite has a greater advantage in reducing the effective cadmium in the soil and the cadmium content in different parts of rice (brown rice, straw and roots) compared with green manure turning and returning to the field, wollastonite alone and other material treatments (goethite, selenium ore powder).

[0053] As can be seen from the above embodiments, the present invention provides a method for synergistically treating cadmium-contaminated soil by using green manure and wollastonite, comprising the following steps: (1) interplanting green manure crops before rice harvest; (2) digging furrows in the field after rice harvest; (3) applying wollastonite before rice seedlings are transplanted, and returning the wollastonite and green manure crops to the field together; (4) irrigating the field for fermentation; (5) applying base fertilizer after fermentation and planting seedlings; (6) applying topdressing during the rice tillering period. The present invention uses green manure to return to the field, thereby improving soil fertility and promoting rice growth. Wollastonite is used to provide silicon fertilizer for the growth and development of rice, while reducing the biological effectiveness of soil cadmium. Green manure and wollastonite work together to effectively reduce the content of effective cadmium in the soil and the content of cadmium in brown rice, so that the synergistic application of green manure and wollastonite in paddy field soil can play a greater role in controlling cadmium.

[0054] 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. A method for synergistically treating cadmium-contaminated soil by using green manure and wollastonite, characterized in that: The steps include: (1) Interplanting green manure crops before rice harvest; (2) After rice is harvested, dig trenches in the fields; (3) Apply wollastonite before rice transplanting and return the wollastonite and green manure crops to the field; (4) Irrigating the fields to make them retting; (5) After the soil is fermented, apply basal fertilizer and plant the seedlings; (6) Apply top dressing during the rice tillering stage.

2. The method according to claim 1, characterized in that The type of green manure crop in step (1) is Chinese Astragalus, and the variety of Chinese Astragalus is Xiangzi No.

1.

3. The method according to claim 2, characterized in that The interseeding time in step (1) is 7 to 10 days before the rice matures, the sowing amount of the green manure crop is 1.5 to 2.0 kg / mu, and during the interseeding, the water on the surface of the rice field is drained and the rice is sown at the bottom.

4. The method according to claim 3, characterized in that The method of digging trenches in step (2) is as follows: digging trenches around the field at the edge of the field, and digging crisscross trenches inside the field. The width of the trenches is 15-25 cm, the depth is 15-25 cm, the intervals between the crisscross trenches are 5-8 m, and the trenches are connected to the drainage outlet.

5. The method according to claim 4, characterized in that The wollastonite in step (3) is spread on the surface of the field when applied, and the amount of wollastonite applied is 180-220 kg / mu.

6. The method according to claim 5, characterized in that The returning to the field treatment in step (3) is carried out by turning over and pressing the soil, and the depth of the turning over and pressing is 15-20 cm.

7. The method according to claim 6, characterized in that The field retting in step (4) is carried out 5 to 10 days after the field returning treatment, and the thickness of the water layer on the field surface is 1 to 2 cm during the field retting.

8. The method according to claim 7, characterized in that The base fertilizer in step (5) is applied 3 to 5 days after the soil is fermented.

9. The method according to claim 8, characterized in that The variety of the rice seedlings in step (5) is Xiangzaoxian 45.

10. The method according to any one of claims 1 to 9, characterized in that: The usage ratio of the base fertilizer in step (5) to the topdressing in step (6) is 3-5:5-7.

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