Method for remedying Cd-polluted soil through giant rice regeneration falling-dry cultivation

Abstract

The invention provides a method for remedying Cd-polluted soil through giant rice regeneration falling-dry cultivation, and belongs to the technical field of soil pollution abatement. The remedying method comprises the steps that in the first half year of the natural year, giant rice is cultivated in a Cd-polluted rice field according to a conventional method; after the giant rice is mature and harvested, 7-20 cm stubbles are reserved, and then irrigation, fertilization and regeneration are conducted; after the tillering stage, water in the rice field is drained, and non-irrigation drying cultivation is carried out; the regenerated giant rice is harvested when mature, and straw is collected and does not return to the field. According to the method, the large-biomass giant rice is selected, and the Cd concentration of the giant rice is increased through drying cultivation, so that the defect that the Cd concentration of large-biomass plants is generally low is overcome, farmland soil Cd is extracted from the plants efficiently at low cost, and low-cost and efficient Cd-polluted soil remediation is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of soil pollution control, and in particular to a method for repairing Cd-contaminated soil by giant rice regeneration and fallen stem cultivation. Background Art

[0002] With the rapid development of social economy, heavy metal pollution caused by unreasonable activities in human production and life is becoming increasingly serious. Among them, cadmium (Cd), as a widely existing heavy metal pollutant, is easy to accumulate in organisms, causing serious pollution to soil, water and crops, and then posing a potential threat to human health through the food chain. Cd pollution in farmland soil has become one of the environmental problems that need to be solved urgently.

[0003] In view of the problem of soil Cd pollution, the existing treatment technologies mainly include physical methods, chemical methods and biological methods. Although physical methods such as soil import method and soil turning method can effectively reduce the Cd content in the soil surface, they are large in engineering volume, high in cost, and may cause secondary pollution; chemical methods such as in-situ passivation remediation and soil leaching remediation, although the effect is significant in the short term, often only treat the symptoms and not the root cause, and the residue of chemical reagents may cause new harm to the environment; biological methods, especially plant remediation technology, have attracted much attention due to their environmental friendliness and relatively low cost, but existing hyperaccumulators such as Southeast Sedum have problems such as small biomass, long growth cycle, low remediation efficiency, and high overall cost, which makes it difficult to promote and apply them in the remediation of large-scale contaminated soil.

[0004] Conventional regenerated rice is a new crop of rice formed by re-tillering and regenerating from the axillary buds on the rice stumps left after the first rice harvest. Conventional regenerated rice can increase the frequency of rice harvests, has a short growth cycle, low production costs, and saves labor and effort. It is an economically feasible and environmentally friendly production method. At present, research on regenerated rice food production issues mainly focuses on how to increase yields and economic benefits, such as variety screening, yield-increasing methods, and the combination of planting and breeding. Research on regenerated rice food security issues mainly focuses on the heavy metal transport characteristics of conventional regenerated rice and measures to reduce the accumulation of heavy metals in regenerated rice. However, researchers have not yet conducted research on the use of regenerated rice for the extraction and remediation of heavy metal contaminated soil.

[0005] Giant rice has a strong regeneration ability and has been successfully applied to vertical cultivation. In Guangdong, both early and late rice can be planted. If the advantages of large biomass of giant rice and increased Cd concentration by drop-stem cultivation can be coordinated and brought into play, efficient plant extraction of Cd may be achieved, forming an innovative restoration model for contaminated soil. Since giant rice production is easier for farmers to accept and implement than hyperaccumulator plants, it can also achieve environmental, social and economic benefits at the same time. Summary of the invention

[0006] In order to overcome the problems existing in the related art, the purpose of the present invention is to provide a method for repairing Cd-contaminated soil by giant rice regeneration and stem dropping cultivation. The method selects giant rice with large biomass and increases the Cd concentration of the giant rice through stem dropping cultivation, thereby overcoming the defect that the Cd concentration of large biomass plants is generally low, and realizes efficient and low-cost plant extraction of Cd from farmland soil, thereby realizing low-cost and efficient soil Cd pollution remediation.

[0007] A method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation, comprising:

[0008] In the first half of the natural year, giant rice was cultivated in the Cd-contaminated paddy fields according to the conventional method;

[0009] After the giant rice matures and is harvested, a stubble of 7cm-20cm is left, and then water and fertilize to regenerate;

[0010] When the rice stubble of giant rice starts tillering again and tillers and plants begin to grow, drain the water from the rice field and practice dry cultivation without irrigation;

[0011] The regenerated giant rice is harvested when it is mature, and the rice straw is taken away and not returned to the field.

[0012] In a preferred technical solution of the present invention, when giant rice is cultivated, the cultivation is carried out under the moisture condition of full flooding or moist soil; wherein, the moisture condition of moist soil is that there are no cracks on the surface of the rice field and the soil surface is in an anaerobic state.

[0013] In a preferred technical solution of the present invention, after the giant rice matures, the height of the rice plant is 160 cm-220 cm.

[0014] In a preferred technical solution of the present invention, the conventional method of cultivating giant rice comprises:

[0015] Transplant the seedlings to the field, with about 4,000 to 6,500 holes planted per mu and 12,000 to 19,500 basic seedlings.

[0016] In a preferred technical solution of the present invention, during the cultivation of giant rice, fertilizer is applied to the giant rice according to conventional rice cultivation methods.

[0017] In a preferred technical solution of the present invention, the regenerated giant rice is harvested when it is mature, and the regenerated giant rice is harvested at a low stubble height of less than 5 cm when it is mature.

[0018] In a preferred technical solution of the present invention, the non-irrigation and drying cultivation includes:

[0019] The groundwater in the rice field is 15cm-50cm below the surface of the rice field to keep the soil surface in an aerobic state.

[0020] In a preferred technical solution of the present invention, after the giant rice is mature and harvested, a stubble of 7 cm to 20 cm is left, and then watering and fertilizing are performed for regeneration, comprising:

[0021] Before irrigation and fertilization for regeneration, dry the field for 2-5 days, then re-water to a water depth of 2cm-3cm.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a method for repairing Cd-contaminated soil by giant rice regeneration and dry cultivation, and the repair method comprises: in the first half of a natural year, giant rice is cultivated in a paddy field contaminated by Cd according to a conventional method; after the giant rice is mature and harvested, a stubble of 7cm-20cm is left, and then watering and fertilizing are applied for regeneration; when the rice piles of the giant rice re-tiller, and the tillers and plants begin to joint, the water in the paddy field is drained, and dry cultivation without irrigation is implemented; the regenerated giant rice is harvested when it is mature, and the rice straw is taken away and not returned to the field. The method selects giant rice with large biomass, and increases the Cd concentration of the giant rice through dry cultivation, thereby overcoming the defect that the Cd concentration of large biomass plants is generally low, and realizes efficient and low-cost plant extraction of farmland soil Cd, thereby realizing low-cost and efficient soil Cd pollution repair. The method is mainly divided into two stages: conventional cultivation of giant rice and non-irrigation and dry cultivation. In the conventional cultivation stage, flooding is adopted to ensure the safe production of rice and meet the food safety standards; in the non-irrigation and dry cultivation stage, Cd is efficiently extracted through dry cultivation, achieving the goal of production and repair, and improving land utilization and economic benefits. In addition, by utilizing the large biomass characteristics of giant rice, its absorption and accumulation capacity of Cd in the soil is significantly improved through dry cultivation, overcoming the defect of low Cd concentration in traditional large biomass plants, and realizing efficient and low-cost plant extraction and repair. Compared with traditional repair methods, the present invention does not require expensive equipment and agents, reducing the repair cost. At the same time, by controlling soil moisture and straw treatment, the risk of environmental pollution is reduced, meeting the requirements of sustainable development, and having broad application prospects and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation provided by the present invention. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0026] Example 1

[0027] Giant rice regeneration and stem cultivation method for remediation of Cd-contaminated soil Figure 1 The present application claims a method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation (Cd refers to cadmium), comprising:

[0028] S100, in the first half of the natural year, giant rice was cultivated in the Cd-contaminated paddy field according to the conventional method;

[0029] Specifically, when giant rice is cultivated, the cultivation is carried out under the moisture conditions of full flooding or moist soil; wherein, the moisture condition of moist soil is that there are no cracks on the surface of the rice field and the soil surface is in an anaerobic state.

[0030] During the cultivation process of full flooding or moist soil, keep the field surface free of cracks to prevent air from entering, thereby maintaining an anaerobic state on the soil surface and reducing the Cd content in native giant rice.

[0031] S200, after the giant rice is harvested, the stubble is 7cm-20cm, and then watering and fertilizing are performed for regeneration; more specifically, before watering and fertilizing for regeneration, the field is first dried for 2-5 days, and then rewatered to a water depth of 2cm-3cm. Leaving stubble of 7cm-20cm can retain more tillering nodes close to the surface, which are important parts for the germination of regenerated rice. The stubble height of this application can protect these growth points to the maximum extent, avoid damage during the harvesting process, and thus ensure the smooth germination of regenerated rice. However, if the stubble is too high, it will cause high-node regeneration, easy lodging and precocity, and small biomass.

[0032] S300, when the rice stubbles of giant rice tiller again and after the tillering period, the water in the rice field is drained, and dry cultivation without irrigation is implemented.

[0033] In actual application, when the tillering of rice reaches about 80% of the expected yield requirement, the field should be dried and the water should be drained in time to gradually expose the field surface.

[0034] Dry cultivation affects the redox potential and bioavailability of Cd in the soil by changing the moisture conditions of the rice fields. Under dry conditions, Cd in the soil is more easily absorbed by the giant rice roots, thereby improving the extraction efficiency of Cd by giant rice. As giant rice grows, especially during the dry cultivation stage, the accumulation of Cd in the plant increases, which helps to remove Cd from the soil through subsequent methods such as harvesting rice straw. Dry cultivation helps the growth and development of the giant rice root system, making the root system more developed and able to absorb water and nutrients from the soil more deeply, while also improving the absorption capacity of Cd. The developed root system enhances the stress resistance of giant rice, including drought resistance and lodging resistance, allowing it to maintain a good growth state under adverse environmental conditions.

[0035] S400, the regenerated giant rice is harvested when it is mature, and the rice straw is taken away and not returned to the field.

[0036] The rice straw can be harvested and not returned to the field, which can reduce the secondary pollution of soil by Cd in the rice straw. At the same time, the rice straw can be treated as a biomass resource and used as non-agricultural fiber material or biomass fuel.

[0037] The above-mentioned method of repairing Cd-contaminated soil by giant rice regeneration and dry cultivation, the method selects giant rice with large biomass, and increases the Cd concentration of giant rice by dry cultivation, thereby overcoming the defect that the Cd concentration of large biomass plants is generally low, and realizing efficient and low-cost plant extraction of farmland soil Cd, thereby realizing low-cost and efficient Cd-contaminated soil remediation. The method is mainly divided into two stages: conventional cultivation of giant rice and dry cultivation without irrigation. In the conventional cultivation stage, flooding growth is adopted to ensure the safe production of rice and meet food safety standards; in the dry cultivation stage without irrigation, Cd is efficiently extracted by dry cultivation, achieving the goal of repairing while producing, and improving land utilization and economic benefits. In addition, by utilizing the large biomass characteristics of giant rice, its absorption and accumulation capacity of Cd in the soil is significantly improved by dry cultivation, overcoming the defect of low Cd concentration of traditional large biomass plants, and realizing efficient and low-cost plant extraction and remediation. Compared with traditional remediation methods, the present invention does not require expensive equipment and agents, reducing the remediation cost. At the same time, by controlling soil moisture and straw processing, the risk of environmental pollution is reduced, which meets the requirements of sustainable development and has broad application prospects and promotion value.

[0038] Furthermore, after the giant rice matures, the height of the rice plant is 160 cm-220 cm.

[0039] Giant rice has a strong regeneration ability and has been successfully applied to three-dimensional cultivation and breeding with the characteristics of significant high yield, lodging resistance, disease and pest resistance, and flooding resistance. In southern my country, both early and late giant rice can be planted. This application coordinates the advantages of giant rice's large biomass and dry cultivation to increase Cd concentration, realizes efficient plant extraction of Cd, and forms an innovative restoration model for contaminated soil. Since giant rice production is easier for farmers to accept and implement than hyperaccumulators, it can also achieve environmental, social, and economic benefits at the same time. Due to its strong tillering ability and large number of panicles, the single-season yield of giant rice can exceed 800 kg / mu.

[0040] Furthermore, the cultivation of giant rice according to a conventional method comprises:

[0041] Transplant the seedlings to the field, with about 4,000 to 6,500 holes planted per mu and 12,000 to 19,500 basic seedlings.

[0042] Furthermore, during the process of cultivating giant rice, fertilizer is applied to the giant rice regularly.

[0043] The regenerated giant rice is harvested when it is mature, and the regenerated giant rice is harvested at a low stubble when it is mature, with a stubble height of less than 5 cm. The surface of the rice field after the low stubble harvest is relatively flat, which is convenient for subsequent field management operations. Further, the non-irrigation and drying cultivation includes:

[0044] The groundwater in the rice field is 15cm-50cm below the surface of the rice field to keep the soil surface in an aerobic state.

[0045] In dry cultivation, keeping the groundwater in the paddy field at a depth of 15cm-50cm below the paddy field surface can keep the soil surface in a relatively dry aerobic state, which helps giant rice to better absorb Cd in the soil.

[0046] Example 2

[0047] This example uses experiments to verify the Cd contaminated soil remediation method of the present application, as follows:

[0048] The pH of the contaminated soil used in the experiment was 5.27; organic matter: 33.51 g / kg; total N: 1.68 g / kg; total P: 0.70 g / kg; total K: 15.58 g / kg; total Cd: 1.186 mg / kg.

[0049] This study was conducted in a ventilated and illuminated net room. Before the experiment began, the soil was sieved through a 2 cm sieve and placed in planting pots. Each pot was filled with 2 kg of air-dried soil. The planting pots were then moved into plastic baskets (80 cm × 60 cm × 40 cm) and the soil was saturated with tap water. Giant rice seedlings were cultivated in plastic culture boxes in advance and transplanted 4 weeks later. The first crop of giant rice was planted under flooded conditions with a 1-2 cm water layer on the soil surface. The planting density was 1 plant / pot, and each plant had 3 seedlings. Harvest when mature, leave about 20 cm of stubble, regenerate, and continue cultivation during the winter idle field period. Three different treatments were set up: (1) flooded cultivation, (2) flooded cultivation + acetic acid, and (3) dry cultivation. The specific experimental settings are shown in Table 1, and each treatment was repeated three times. The above-mentioned flooding means: keeping the water surface 1-2 cm higher than the soil surface; the drying means: growing under moist moisture conditions in the early stage, and draining after the tillering period to make the water surface 10-15 cm lower than the soil surface; the amount of acetic acid added: adding 20 ml of glacial acetic acid to each pot (2 kg of soil).

[0050] Table 1 Design of implementation plan for potted plant experiment

[0051]

[0052] The primary and regenerated giant rice were collected separately as grains and stalks, and their biomass and moisture content were measured. After the rice was harvested, the topsoil was collected with a soil sampler and dried naturally in a pollution-free place.

[0053] Plant samples from different parts were fixed in an oven at 70°C for 30 min, dried at 55°C to constant weight, crushed with a grinder, passed through a 100-mesh sieve, and placed in a sealed plastic bag. Soil samples were collected by the quartering method and visible plant roots were picked out. After grinding with an electric agate mortar, the samples were passed through 20-mesh and 100-mesh sieves and stored in sealed bags.

[0054] Total Cd in plants and soil was determined by microwave digestion-flame or graphite furnace atomic absorption spectrophotometry (HITACHI, Z-2700 / Z-2300) according to the national standard method (GB5009.15-2014) and environmental standard method (HJ832-2017), and the results were verified by national standard substances (GBW(E)100348a) and (GBW07405a). -1 Calcium chloride (DB35 / T860-2008) was used to extract the available Cd in the soil, and the Cd concentration in the extract was determined by a graphite furnace atomic absorption spectrophotometer. The soil pH was determined by a pH meter, with a water-soil ratio of 2.5:1.

[0055] The biomass and Cd content of giant rice under different treatments are shown in Table 2. Compared with the newly grown rice, the biomass of winter regenerated giant rice decreased (the blank group decreased by 39% under flooding conditions). In the regenerated rice, the addition of acetic acid reduced the biomass of giant rice straw compared with the blank group, while the dry condition had no significant effect on the biomass of giant rice. Under flooding conditions, the Cd content of the grain and straw of newly grown giant rice was low, 0.030 and 0.274 mg kg, respectively. -1 , rice is within the safety standard (≤0.2mg·kg -1 ) range. Under flooding conditions, the Cd concentration in the straw of giant rice was lower, at 0.362 mg kg -1 After adding acetic acid, the Cd concentration in the regenerated giant rice straw increased significantly to 3.86 mg kg -1 Under the condition of falling and drying, the Cd concentration of regenerated giant rice straw was the highest, which was 12.54 mg kg -1 .

[0056] Table 2 Biomass and Cd content of giant rice under different treatments

[0057]

[0058] Note: In the second giant rice regeneration treatments, T1 was flooding, T2 was flooding + acetic acid, and T3 was drying. Data are expressed as mean ± standard deviation (n = 3). Since the treatments of primary giant rice were exactly the same, the Cd content shared a set of data.

[0059] The above results show that flooding the first-crop giant rice can produce Cd-safe rice. In the second-crop regenerated rice, the effect of adding acetic acid on increasing the Cd concentration in the straw is not ideal; while the use of drop-drying conditions can significantly increase the Cd concentration in the straw, which is helpful for extracting soil Cd using regenerated giant rice.

[0060] In terms of the amount of Cd extracted by giant rice (Table 3), the amount of Cd extracted from soil by regenerated giant rice straw under flooding conditions was extremely low, at 0.0123 mg / plant. -1 ; Adding acetic acid or keeping the drying condition significantly increased the Cd extraction of regenerated giant rice straw, with the extraction of single plant reaching 0.1099 and 0.4382 mg, respectively. The extraction rate of regenerated giant rice from soil Cd was 4 times that of adding acetic acid, reaching 5.36% and 19.20%, respectively, indicating that the effect of drying on improving the extraction of Cd from regenerated giant rice was better than that of adding acetic acid. The removal rates of soil Cd by T2 and T3 obtained from the soil were 11.01% and 18.14%, respectively. The results showed that the removal effect of soil Cd by regenerated giant rice from soil was better than that of adding acetic acid (flooding).

[0061] Table 3 Cd extraction amount of giant rice and soil Cd removal rate under different treatments

[0062]

[0063] Note: In the second giant rice regeneration treatments, T1 was flooding, T2 was flooding + acetic acid, and T3 was drying. Extraction rate = plant extraction amount / initial soil total content; removal rate = soil reduction amount / initial soil content.

[0064] Example 3

[0065] This example uses three test products, namely Zengcheng silk seedlings, giant rice, and royal bamboo grass seed stems, to verify the Cd-contaminated soil remediation method of the present application, as follows:

[0066] The test soil properties are shown in Table 4.

[0067] Table 4 Chemical properties and Cd content of the tested soils

[0068]

[0069] Note: Data are expressed as mean ± standard deviation (n = 3).

[0070] The experiment set up 4 treatments, each of which was repeated three times and randomly arranged. As shown in Table 5, T1: Silk seedlings were planted in both the first and second half of the year as a control of conventional rice, with flooding in the first half of the year and dry cultivation in the second half of the year; T2: Giant rice was planted in the first half of the year and replanted in the second half of the year, with the same water management; T3: Giant rice was planted in the first half of the year and regenerated in the second half of the year, with the same water management; T4: Giant rice was planted in the first half of the year and King bamboo grass was planted in the second half of the year, with the same water management.

[0071] The soil column (PVC tube) has an inner diameter of 15 cm and a height of 50 cm. From bottom to top, the structure is: quartz sand (5 cm), non-contaminated soil (20 cm), and Cd-contaminated soil (20 cm). Before the experiment, the soil was sieved through a 2 cm sieve and then loaded into the soil column. The soil bulk density was 1.25 g cm -3 4.5 kg of soil was used for each layer. The soil column was moved into a large plastic water tank (800 L, 150 cm × 120 cm × 60 cm) and the soil was saturated with tap water.

[0072] Rice seedlings were transplanted after 4 weeks of seedling raising in plastic incubators. One seedling was planted in each soil column, and each column had 3 seedlings. 5 cm long seed stems of King Bamboo Grass were cut for seedling raising first, and transplanted at the same time as rice. During the first half of the year, the water level was kept at 1-2 cm throughout the planting process; during the early planting period of the second half of the year, the water level was kept at 1-2 cm, and the soil was dried after the tillering period (the water level was kept 15-20 cm below the soil surface).

[0073] Table 5 Design of soil column test implementation plan

[0074]

[0075] When the grass is harvested, its aboveground biomass and moisture content are measured. For primary and regenerated rice, the seeds and stalks are collected separately, and their biomass and moisture content are measured. After the plants are planted, the topsoil is collected with a soil sampler and dried naturally in a pollution-free place.

[0076] The results are shown in Table 6. Under the condition of late rice drying, compared with the new rice (early rice and late rice), the grain biomass of the regenerated giant rice decreased, the straw harvest did not change significantly, and the grass with the largest biomass was King Grass.

[0077] Table 6 Biomass and Cd concentration of plants under different treatments

[0078]

[0079]

[0080] Note: Data are expressed as mean ± standard deviation (n = 3). The Cd concentration in the second half of the year is the weighted average of the results of the two tests. Duncan test was used, and different letters in the same row indicate significant differences (P < 0.05).

[0081] Under the flooding condition of early rice, the Cd concentrations in the seeds of giant rice and silk seedlings were relatively low, which were 0.008 and 0.006 mg·kg, respectively. -1 , the rice meets the food safety standards. Under the condition of late rice drying, the Cd concentration in the grains of giant rice (new or regenerated) and silk seedlings is high and is not suitable for food. Under the condition of drying, the Cd concentration in the regenerated giant rice straw is 16.03 mg kg -1 , which was significantly higher than that of newly grown giant rice, silk seedlings and royal bamboo grass. The above results show that the first-sown giant rice grown in flooding can produce Cd-safe rice. The Cd concentration in the straw of the regenerated giant rice grown on the ground was significantly higher than that of silk seedlings and royal bamboo grass.

[0082] The results of plant extraction in Table 7 show that under the flooding condition of early rice, the extraction of soil Cd by giant rice and silk seedling straw was extremely low. Under the drying condition of late rice, the extraction of soil Cd by straws of different treatments increased significantly, and the differences were significant. The Cd extraction of imperial bamboo grass and silk seedling straw was 0.5336 and 0.3521 mg / pot, respectively, which was significantly lower than that of giant rice. For giant rice, the Cd extraction of regenerated rice was 1.98 times that of the original, which was 1.168 and 0.589 mg / pot, respectively.

[0083] Table 7 Cd extraction amount of plants under different treatments (mg / pot)

[0084]

[0085] Note: Data are expressed as mean ± standard deviation (n = 3). Duncan test was used, and different letters in the same row indicate significant differences (P < 0.05). Extraction rate = plant extraction amount / initial soil total content.

[0086] The Cd plant extraction rates of T1 / T2 / T3 / T4 were 8.55%, 13.08%, 23.17% and 9.60%, respectively, that is, the plant extraction efficiency of soil Cd was: regenerated giant rice> giant rice> royal bamboo grass> silk seedlings. These results show that for giant rice, the Cd extraction effect of stem-dropped growth after regeneration is better than that of giant rice replanting, and is also significantly better than royal bamboo grass with larger biomass. The plant extraction rate of regenerated giant rice reached 23%, which is also higher than most reported results of potted Sedum alfredii, indicating that regenerated giant rice has a good ability to extract soil Cd.

[0087] The Cd pollution concentration of the experimental surface soil used in this study was 1.186 mg kg -1, which belongs to moderately Cd-contaminated soil. As shown in Table 8, after remediation, the removal efficiencies of soil Cd in T1, T2, T3, and T4 were 14.04%, 20.96%, 30.50%, and 21.66%, respectively. The removal efficiency of soil Cd by T2 was better than that of T1, indicating that the removal efficiency of soil Cd by giant rice was significantly better than that of ordinary rice (silk seedlings). Comparing T2 / T3 / T4, the removal efficiency of soil Cd by plants was: regenerated giant rice>giant rice≈king grass. The results show that under the condition of drying, the remediation effect of regenerated giant rice on soil Cd was significantly better than that of new giant rice and king grass. Therefore, the drying growth of regenerated giant rice has a good removal effect on soil Cd.

[0088] Table 8 Effects of different plant treatments on soil Cd and its removal rate (mg kg -1 )

[0089]

[0090] Note: Data are expressed as mean ± standard deviation (n = 3); T2 / T3 / T4 are exactly the same in the first half of the year and share a set of data. Removal rate = soil reduction / soil initial content.

[0091] Regenerated rice does not require tilling, sowing, or transplanting. It has fewer pests and diseases, and usually does not require spraying of pesticides. It only requires topdressing with fertilizer once before the first harvest (7-10 days) and once after the harvest (2-3 days). Therefore, the production cost of regenerated giant rice is low, labor-saving, and an economically feasible restoration method.

[0092] In summary, this application has originally proposed the safe utilization + plant restoration planting model of giant rice "primary rice flooded growth + regenerated rice dry cultivation", which can achieve the goal of "safe rice production in the first stage and efficient Cd extraction in the second stage". This method can achieve low-cost and efficient extraction and restoration of soil Cd, and can achieve simultaneous production and restoration, providing new ideas and methods for the restoration of Cd-contaminated soil, and has important promotion value.

[0093] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation, characterized in that: include: In the first half of the natural year, giant rice was cultivated in the Cd-contaminated paddy fields according to the conventional method; After the giant rice matures and is harvested, a stubble of 7cm-20cm is left, and then water and fertilize to regenerate; When giant rice tillers again and after the tillering period, drain the paddy field and practice dry cultivation without irrigation; The regenerated giant rice is harvested when it is mature, and the rice straw is taken away and not returned to the field.

2. The method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 1, characterized in that: When giant rice is cultivated, full flooding or moist soil conditions are used for cultivation; among them, moist soil conditions are that there are no cracks on the rice field surface and the soil surface is in an anaerobic state.

3. The method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 1, characterized in that: When the giant rice is mature, the height of the rice plant is 160 cm to 220 cm.

4. The method for repairing Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 3, characterized in that: The method of cultivating giant rice according to the conventional method comprises: Transplant the seedlings to the field, with about 4,000 to 6,500 holes planted per mu and 12,000 to 19,500 basic seedlings.

5. The method for remediating Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 1, characterized in that: The regenerated giant rice is harvested when it is mature, and the regenerated giant rice is harvested at a low stubble height of less than 5 cm when it is mature.

6. The method for remediating Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 1, characterized in that: The non-irrigation and drying cultivation comprises: The groundwater in the rice field is 15cm-50cm below the surface of the rice field to keep the soil surface in an aerobic state.

7. The method for remediating Cd-contaminated soil by giant rice regeneration and stem cultivation according to claim 1, characterized in that: After the giant rice is harvested, a stubble of 7 cm to 20 cm is left, and then watering and fertilizing are performed for regeneration, including: Before irrigation and fertilization for regeneration, dry the field for 2-5 days, then re-water to a water depth of 2cm-3cm.

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