A fertilizer for reducing cadmium content in paddy brown rice and a method for applying the same

Abstract

The application discloses a kind of fertilizer for reducing the content of cadmium (Cd) in rice brown rice and its application method, including 34% of slaked lime, 30% of iron nitrate nonahydrate, 28% of calcium silicate, 5% of potassium sulfate and 3% of magnesium sulfate are uniformly mixed at normal temperature and normal pressure to be made, and the rice compound fertilizer is uniformly applied to the paddy field where rice is needed to be planted and ploughed uniformly, then the finished product Cd reducing fertilizer is scattered, and then the field is raked, finally, the paddy field is flooded and idle for 5 days, and then rice seedling shallow water transplanting is carried out, and the rice compound fertilizer is applied by artificial scattering method 1 time each time for topdressing on the 7th day and the 20th day after rice transplanting; The water layer is kept 2-3 cm during the growth period of rice, and the water layer in the paddy field is drained and the field is dried one week before harvesting.The fertilizer prepared by the application has low cost and is easy for farmers to obtain, and when the fertilizer is applied in the paddy field with weak acid soil (soil 5.5

Description

Technical Field

[0001] This invention relates to the field of rice cultivation technology, specifically to a fertilizer for reducing the Cd content in brown rice and its application method. Background Technology

[0002] Industrialization and inadequate environmental protection measures since the 1990s have led to a worsening of heavy metal pollution in farmland soils in some parts of my country. According to the 2014 National Soil Pollution Survey Bulletin jointly released by the former Ministry of Environmental Protection and the former Ministry of Land and Resources, the exceedance rate of arable land soil sampling points was 19.4%, with light to moderate pollution accounting for 94.3% of the exceedance points. Pollution levels in the south were generally higher than in the north. Cd pollution in paddy field soil often leads to excessive Cd levels in rice, seriously endangering human health. The remediation of Cd pollution in paddy fields is currently a key focus and a difficult challenge in the overall control of heavy metal pollution in farmland in my country.

[0003] In South my country, most paddy field soils are acidic, making them highly reactive with cadmium (Cd). Currently, the most commonly used technique for remediating paddy fields contaminated with moderate to mild Cd is the application of soil amendments. This technique involves adding alkaline materials to the soil to increase its pH value, or using highly absorbent materials to increase the soil's adsorption capacity for Cd, thereby effectively reducing the bioavailability of Cd in the soil and ultimately reducing the accumulation of Cd in brown rice. Nearly a hundred soil amendments have been reported, but none have yet been widely applied or promoted. One important reason is that while these amendments reduce the Cd content in brown rice, they can also affect the soil's physicochemical properties and fertility, posing a risk of reducing the soil's productivity. Alternatively, using molecular biology techniques to modify the rice genome through breeding engineering to reduce Cd accumulation in brown rice is also an effective technique for the safe utilization of Cd-contaminated paddy fields in recent years. However, these technologies face limitations in widespread adoption by numerous farmers and in agricultural production. Furthermore, their use can alter the rice genome and potentially reduce the accumulation of nutrients such as iron, manganese, and zinc in brown rice, thus lowering rice quality. Third, planting *Sedum aizoon* and *Sedum sarmentosum* can effectively reduce Cd content in the soil, thereby decreasing Cd accumulation in brown rice. However, due to a series of currently insurmountable difficulties in sowing, flood control, weed control, disease management, low biomass, and post-harvest processing, *Sedum aizoon* and *Sedum sarmentosum* are not suitable materials for the remediation of large-scale Cd-contaminated paddy fields. Therefore, we propose a fertilizer and its application method to reduce Cd content in brown rice to address the above problems. The main goal is not only to provide sufficient nutrients for rice growth but also to effectively reduce Cd accumulation in brown rice, ensuring rice food safety. Summary of the Invention

[0004] The purpose of this invention is to provide a fertilizer and its application method for reducing the Cd content in brown rice, so as to solve the difficulties and problems existing in the above-mentioned background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a fertilizer for reducing the Cd content in brown rice, wherein the raw material composition, by mass percentage, includes: 30%-35% quicklime, 28%-32% ferric nitrate nonahydrate, 25%-30% calcium silicate, 4%-7% potassium sulfate and 2%-5% magnesium sulfate.

[0006] In a preferred embodiment, the raw material composition, by mass percentage, includes: 34% quicklime, 30% ferric nitrate nonahydrate, 28% calcium silicate, 5% potassium sulfate, and 3% magnesium sulfate.

[0007] In a preferred embodiment, the fertilizer is prepared by uniformly mixing quicklime, ferric nitrate nonahydrate, calcium silicate, potassium sulfate, and magnesium sulfate at room temperature and pressure according to their mass percentages to obtain the finished Cd-reducing fertilizer.

[0008] A method for applying a fertilizer to reduce the Cd content in brown rice, characterized by comprising the following steps:

[0009] (1) Pretreatment of paddy fields

[0010] Apply compound fertilizer for rice evenly to the paddy field where rice needs to be planted and plow it evenly. Then spread the finished Cd-reducing fertilizer, harrow the field, and finally flood the paddy field with a water layer thickness of 2-3cm.

[0011] (2) Rice transplanting

[0012] After the paddy field was flooded and left idle for 5 days, the rice seedlings were transplanted in shallow water. On the 7th and 20th day after transplanting, compound fertilizer for rice was applied manually once each.

[0013] (3) Moisture Management

[0014] During the rice growing season, the water level is maintained at 3cm. A week before harvest, the water level in the paddy field is drained and the field is dried.

[0015] In a preferred embodiment, in step (1), the Cd-reducing fertilizer is applied evenly by manual or mechanical means, and the amount of fertilizer applied is 214 kg / mu.

[0016] In a preferred embodiment, in steps (1) and (2), the nutrient content of the rice compound fertilizer satisfies N+P2O5+K2O≥31%.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] (1) The fertilizer prepared in this invention can significantly reduce the Cd content in brown rice when applied to paddy fields with weakly acidic soil (soil 5.5 < pH ≤ 6.5) and moderate to mild Cd pollution, so that it meets the national standard (National Food Safety Standard Limits for Contaminants in Food (GB2762-2017)) and ensures food security.

[0019] (2) The fertilizer prepared in this invention is made by uniformly mixing five kinds of fertilizers that are more common in rice planting in my country under normal temperature and pressure conditions in a certain mass ratio. It is low in cost, easy for farmers to obtain, and easy to promote.

[0020] (3) The fertilizer prepared in this invention is only applied once 5 days before the rice seedlings are transplanted, and is not applied again during the entire growth period of rice, which reduces the frequency of fertilizer application and labor input, making it easier for farmers to accept.

[0021] (4) The fertilizer prepared in this invention can be applied by both manual and mechanical application methods, which is flexible and convenient for farmers to implement. Attached Figure Description

[0022] Figure 1 This is a graph showing the content of available Cd in the rhizosphere soil under different treatments at the maturity stage of this invention.

[0023] Figure 2 This is a graph showing the cumulative amount of Cd in rice under different treatments at the maturity stage according to the present invention.

[0024] Figure 3 This is a distribution diagram of Cd in rice under different treatments at the maturity stage according to the present invention;

[0025] Figure 4 This refers to the translocation coefficients of Cd from different organs of rice to brown rice during different treatments at the maturity stage of this invention.

[0026] Figure 5 The content of Cd in brown rice from rice treated at different maturity stages according to this invention;

[0027] Different lowercase letters in the figure indicate significant differences between treatments (P<0.05). Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Please see Figure 1-5 This invention provides a technical solution: a fertilizer for reducing the Cd content in brown rice, comprising, by mass percentage: 34% quicklime, 30% ferric nitrate nonahydrate, 28% calcium silicate, 5% potassium sulfate and 3% magnesium sulfate. The quicklime, ferric nitrate nonahydrate, calcium silicate, potassium sulfate and magnesium sulfate are uniformly mixed by mass percentage under normal temperature and pressure conditions to obtain the finished Cd-reducing fertilizer.

[0030] A method for applying a fertilizer to reduce the Cd content in brown rice, characterized by comprising the following steps:

[0031] (1) Pretreatment of paddy fields

[0032] Apply compound fertilizer for rice evenly to the paddy field where rice needs to be planted and plow it evenly. Then, spread the finished Cd-reducing fertilizer at a rate of 214 kg / mu. Then harrow the field and finally flood the paddy field with a water layer thickness of 2-3 cm.

[0033] (2) Rice transplanting

[0034] After the paddy field was flooded and left idle for 5 days, the rice seedlings were transplanted in shallow water. On the 7th and 20th day after transplanting, compound fertilizer for rice was applied manually once each.

[0035] (3) Moisture Management

[0036] During the rice growing season, the water level is maintained at 2-3 cm. A week before harvest, the water level in the paddy field is drained and the field is dried.

[0037] Furthermore, in steps (1) and (2), the nutrient content of the rice compound fertilizer satisfies N+P2O5+K2O≥31%.

[0038] To demonstrate the effectiveness of the fertilizer and application method of this invention, a pot experiment was conducted to compare the treatment group and the control group. Paddy soil was collected, air-dried, ground, and passed through a 2cm nylon sieve before being used as the test soil for the pot experiment. The physicochemical properties of the soil were as follows: pH 6.0, organic matter 37.2 g / kg, cation exchange capacity (CEC) 6.8 cmol(+) / kg, clay (<0.002 mm) 8.0%, silt (0.05-0.002 mm) 32.4%, sand (2-0.05 mm) 59.6%, available nitrogen 179.2 mg / kg, available phosphorus 51.6 mg / kg, available potassium 155.5 mg / kg, and total Cd 1.4 mg / kg. In the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), when the pH value of paddy fields is 5.5 < pH ≤ 6.5, the risk screening value of Cd in the soil is 0.4 mg / kg. According to this standard, the Cd content in the tested soil in this experiment exceeds the pollution risk screening value by 3.5 times, indicating that it is moderately polluted by Cd. A pot experiment was conducted in a greenhouse. The treatment group was treated with the Cd-reducing fertilizer of this invention, while the control group was not treated with the Cd-reducing fertilizer of this invention. Each treatment was repeated 3 times. The rice variety used in the experiment was Maba Youzhan, which is a conventional rice variety widely planted in southern my country.

[0039] Rice seedlings were first raised in seedling trays in a greenhouse. When the seedlings reached the three-leaf stage, they were immediately transplanted, with one seedling transplanted into each experimental tray. The experimental trays used in the experiment were made of PVC pipe, with dimensions of 25cm in height and 15cm in diameter, and contained 4.0kg of soil. The root zone bags used in the experiment were made of nylon mesh with a pore size of 20μm, with dimensions of 15cm in height and 8cm in diameter, and contained 1.0kg of soil. The root zone bags were placed in the center of the experimental trays, with 1.0kg of soil inside the bags and 3.0kg of soil outside the bags.

[0040] In the control group, 4.0 kg of paddy soil was mixed evenly with 0.7 g of compound rice fertilizer beforehand. This mixture was then slowly poured into a test pot, and tap water was slowly added to maintain a water layer thickness of 2-3 cm. After 5 days of rest, rice seedlings were transplanted. The same procedure was performed in two other test pots. During the experiment, 0.7 g of compound rice fertilizer was added to the water layer in each test pot on the 7th and 20th days after transplanting, respectively. Throughout the rice's growth period, except for the week before harvest when the water layer was drained to simulate field drying, the water layer was maintained at 2-3 cm.

[0041] In the treatment group, 4.0 kg of paddy soil was mixed evenly with 0.7 g of rice compound fertilizer beforehand, and then 5.7 g of the fertilizer described in this invention was evenly mixed in. The mixture was then slowly poured into a test pot. The subsequent operating procedures and methods were exactly the same as those in the control group.

[0042] On the day of rice harvest, rhizosphere soil and plant samples were collected from both the control and treatment groups. For the rhizosphere soil, the content of available Cd in the soil was determined using the ammonium acetate extraction method. For the plant samples, the roots were carefully separated, and the iron film on the root surface was removed using the DCB method. The fresh weight of the roots was then measured, followed by blanching, drying, pulverizing, and digestion. The Cd content in the digestion solution was determined using a graphite furnace atomic absorption spectrometer (PEAA600). Next, stems, leaves, nodes, and husks were separated from the plant samples, weighed, and then subjected to blanching, drying, pulverizing, and digestion. The Cd content in the digestion solution was determined using a graphite furnace atomic absorption spectrometer (PEAA600). Finally, the separated brown rice samples were first pulverized and digested, and then the Cd content in the digestion solution was determined using ICP-MS (Agilent Technologies 7800).

[0043] Based on the measurement data of available Cd content in rhizosphere soil, the differences in available Cd content between the control group and the treatment group were analyzed. Furthermore, based on the measurement data of Cd content in roots, stems, leaves, nodes, husks, and brown rice, the distribution characteristics of Cd within rice were analyzed, and the translocation coefficients (TFs) of Cd from different tissues of rice to brown rice were calculated. Statistical analysis was performed using SPSS 17.0, and graphs were generated using OriginPro 8.1.

[0044] Calculation of translocation coefficient: TF = C 糙米 / C 器官 Where TF is the transport coefficient, and C 糙米 The Cd content (mg / kg) in brown rice. 器官 The Cd content (mg / kg) in different tissues and parts of rice.

[0045] from Figure 1 It can be seen that the treatment group significantly reduced the content of available Cd in the rhizosphere soil at maturity. Compared with the control group, the content of available Cd in the rhizosphere soil of the treatment group decreased by 92.8%.

[0046] from Figure 2 It can be seen that the treatment group significantly reduced the accumulation of Cd in rice at maturity. Compared with the control group, the accumulation of Cd in rice in the treatment group was reduced by 69.8%.

[0047] from Figure 3It can be seen that the treatment groups significantly altered the distribution pattern of Cd in rice: in the control group, the distribution pattern of Cd was stem > root > brown rice > husk > leaf > nodule; however, in the treatment groups, the distribution pattern of Cd was root > stem > brown rice > leaf > husk > nodule. Furthermore, compared with the control group, the treatment groups significantly increased the proportion of Cd in roots, leaves, and brown rice, but significantly decreased the proportion of Cd in stems, nodules, and husks.

[0048] from Figure 4 It can be seen that the treatment groups significantly enhanced the Cd translocation capacity of stems and shells, but significantly weakened the Cd translocation capacity of leaves. Furthermore, there was no significant difference in the Cd translocation capacity of roots and nodules between the control and treatment groups.

[0049] from Figure 5 It can be seen that the treatment group significantly reduced the Cd content in brown rice at maturity. Compared with the control group, the Cd content in brown rice of the treatment group decreased by 67.4%. Furthermore, the Cd content in brown rice of the treatment group was 0.09 mg / kg, which is significantly lower than the limit value (0.2 mg / kg) for Cd in brown rice in the National Food Safety Standard (GB2762-2017), thus meeting the national food safety standard.

[0050] Conclusion: The application of the fertilizer described in this invention effectively reduced the content of available Cd in the rhizosphere soil of rice; effectively reduced the accumulation of Cd in rice plants; increased the distribution ratio of Cd in roots and leaves, but decreased the distribution ratio of Cd in stems, nodes, and husks; enhanced the ability of stems and husks to translocate Cd to brown rice, but weakened the ability of leaves to translocate Cd to brown rice, while having no significant effect on the ability of roots and nodes to translocate Cd to brown rice. The combined effect of these four aspects significantly reduced the accumulation of Cd in brown rice, bringing the Cd content in brown rice to meet the national food safety standard (Cd < 0.2 mg / kg).

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fertilizer for reducing Cd content in brown rice, comprising, by weight percentage: 30%-35% quicklime, 28%-32% ferric nitrate nonahydrate, 25%-30% calcium silicate, 4%-7% potassium sulfate and 2%-5% magnesium sulfate.

2. The fertilizer for reducing Cd content in brown rice according to claim 1, wherein the raw material composition, by mass percentage, comprises: 34% quicklime, 30% ferric nitrate nonahydrate, 28% calcium silicate, 5% potassium sulfate and 3% magnesium sulfate.

3. The fertilizer for reducing Cd content in brown rice according to claim 1, characterized in that: The fertilizer is prepared by uniformly mixing quicklime, ferric nitrate nonahydrate, calcium silicate, potassium sulfate, and magnesium sulfate at room temperature and pressure according to their mass percentages to obtain the finished Cd-reducing fertilizer.

4. A method for applying a fertilizer to reduce the Cd content in brown rice according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Pretreatment of paddy fields Apply compound fertilizer for rice evenly to the paddy field where rice needs to be planted and plow it evenly. Then spread the finished Cd-reducing fertilizer, harrow the field, and finally flood the paddy field with a water layer thickness of 2-3cm. (2) Rice transplanting After the paddy field was flooded and left idle for 5 days, the rice seedlings were transplanted in shallow water. On the 7th and 20th day after transplanting, compound fertilizer for rice was applied manually once each. (3) Moisture Management During the rice growing season, the water level should be maintained at 2-3 cm. One week before harvest, the water level in the paddy field should be drained and the field should be dried. The Cd-reducing fertilizer mentioned in step (1) is applied evenly by manual or mechanical means, and the application rate of the fertilizer is 214 kg / mu; The nutrient content of the rice compound fertilizer described in steps (1) and (2) satisfies N+P2O5+K2O≥31%.

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