Seedling raising and cultivation method for synergistically reducing cadmium content of tomato fruits

Abstract

The invention discloses a seedling raising and cultivation method for synergistically reducing the cadmium content of tomato fruits, and belongs to the technical field of agricultural environment safety. The method comprises the following steps: mixing biochar and seedling culture nutrient soil to prepare a biochar-containing seedling culture substrate; cultivating solanum torvum rootstock seedlings in the matrix; grafting a tomato scion to the stock to obtain a grafted seedling; and finally, transplanting the grafted seedlings together with the biochar-containing seedling substrate at the roots of the grafted seedlings into cadmium-polluted soil for cultivation. According to the method, the biochar is locally used in the seedling raising stage and is combined with a rootstock grafting technology with the low-cadmium characteristic, the dual synergistic effect from rhizosphere fixing to in-vivo blocking is achieved, the cadmium content of tomato fruits can be remarkably reduced, the use amount is small, the cost is low, operation is easy and convenient, and no negative influence is generated on the crop yield and quality; and an effective solution is provided for safe utilization of the cadmium-polluted cultivated land.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of agricultural environmental safety and safe production of agricultural products, and particularly relates to a tomato cultivation method for cadmium contaminated soil, in particular to a seedling raising and cultivation method for synergistically reducing cadmium content in tomato fruits. BACKGROUND

[0002] Cadmium (Cd) is a common toxic heavy metal pollutant in farmland soil, which can be enriched through the food chain and seriously endanger human health. In China, cadmium (Cd) contaminated farmland reaches 128 million mu, with more than 90% of low and medium concentration pollution, which has brought adverse effects on grain yield and quality. Therefore, how to produce qualified agricultural products in Cd contaminated soil and realize the safe use of Cd contaminated soil has become a major environmental problem that needs to be solved urgently in China. The basic goal of safe use of Cd contaminated soil is to achieve multiple barriers to Cd at the soil, rhizosphere, and body transport stages, which is essentially the use of land resources, not site remediation. Currently, common remediation methods such as soil replacement, chemical fixation, or hyperaccumulator plant remediation have many limitations and shortcomings: high cost, large soil disturbance, long remediation period, etc., which affect normal agricultural production.

[0003] Biochar is a material for fixing soil Cd and is widely used in soil remediation. However, current in-situ remediation often adds 1-5% of biochar based on the quality of farmland soil, which has high cost and ecological risk at high dosage. In practical application, it needs to be combined with the degree of pollution and used with other safe use technologies to reduce the dosage of biochar while improving the effect of Cd control.

[0004] Grafting is a conventional plant propagation method in horticulture, which has been widely used for a long time in crop yield increase, disease resistance, and improvement of agricultural product quality. The principle is to use plants with well-developed root systems and good disease resistance as rootstocks to improve the quality and yield of grafted crop fruits. In recent years, research has found that rootstocks can affect the absorption and transport of soil heavy metals in crops (Lizong Sun, Chunyun Jia, Chenyang Xue, et al. Mechanism and stability of low cadmium accumulation in grafted soybeans induced by rootstocks, Plant and Soil, 2023, 483: 313-329.). This means that by selecting suitable rootstock varieties and using grafting methods, the Cd content in the edible parts of grafted crops can be reduced.

[0005] Tomato is widely planted in the world, and the annual output of tomato in China is about 7200 tons, accounting for 7% of the total amount of vegetables. Nearly ten million mu of cultivated land in China is polluted by heavy metals to varying degrees, and it is unrealistic to completely repair them in a short time. Therefore, finding a method to produce qualified agricultural products on contaminated farmland is the key to safely utilizing large areas of contaminated soil. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art and provide a seedling and cultivation method for synergistically reducing the cadmium content of tomato fruits, which has the characteristics of low cost, stable effect and simple operation, can block and control the transportation of soil Cd to the aboveground part of crops, and realizes the safe utilization of Cd contaminated soil.

[0007] To solve the above technical problems, the present application is implemented as follows: A seedling and cultivation method for synergistically reducing the cadmium content of tomato fruits, comprising the following steps: (1) mixing biochar with seedling nutrient soil to obtain seedling substrate containing biochar; (2) seedling in the seedling substrate containing biochar of step (1) with Torulbaum as stock; (3) seedling with tomato as scion; (4) grafting the tomato scion cultivated in step (3) onto the Torulbaum stock cultivated in step (2) to obtain grafted seedlings; (5) transplanting the grafted seedlings of step (4) together with the biochar-containing seedling substrate of their roots into cadmium-contaminated soil for cultivation.

[0008] Further, the biochar is a biochar prepared by pyrolysis of biomass waste under high temperature and anaerobic conditions.

[0009] Further, the biochar is rice husk biochar, and the pyrolysis temperature is 600-800°C.

[0010] Further, in step (1), the addition amount of biochar is 2-5% of the mass of the seedling nutrient soil.

[0011] Further, in step (2), the sowing time of Torulbaum is 25-35 days earlier than that of tomato.

[0012] Further, in step (4), the grafting is performed by wedge grafting when the Torulbaum stock grows to 5-6 leaf age and the tomato scion is at the cotyledon stage to the two-true-leaf stage.

[0013] Further, in step (5), the grafted seedlings of step (4) are subjected to hardening treatment before transplanting, and the hardening treatment comprises culturing in a light-shielded and high-humidity environment for 1-15 days.

[0014] Compared with the prior art, the present application has the following advantages: 1、The rhizosphere fixation of biochar and the physiological barrier effect of rootstock are closely combined in time and space in the present application. Compared with the effect of fixing soil Cd by using biochar alone, the reduction rate of Cd in fruits by the biochar combined grafting technology involved in the present application is more than twice that of the former. Meanwhile, compared with the current biochar fixation technology (adding biochar at 1-5% of the quality of arable land soil), the present application (adding biochar at 4% of the quality of the seedling nutrient soil) significantly reduces the use amount of biochar, has little disturbance to the arable land soil environment, and has the effect of reducing cost and increasing efficiency.

[0015] 2、The present application can reduce the Cd content in tomato fruits planted in Cd contaminated arable land by more than 85%, while the effect achieved by other measures (such as improving soil pH, phytoremediation, soil leaching, etc.) is often less than 50% (Arao T. Reduction of cadmium translocation from roots to shoots in eggplant (Solanum melongena) by grafting onto Solanum torvum rootstock, Soil Science and Plant Nutrition, 2008, 54(4): 555-559).

[0016] 3、The rootstock material used in the present application is easy to obtain and cultivate, and the grafting method used is simple to operate, without the need for expensive experimental reagents, and the professional knowledge requirement for the operator is not high. More importantly, the present application can reduce the Cd content in tomato fruits without affecting the quality and yield of tomatoes. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The present application is an embodiment of a grafting incision healing diagram with Solanum torvum as the rootstock and tomato as the scion. DETAILED DESCRIPTION

[0018] The present application will be described in detail below through specific embodiments. These embodiments are provided in order to enable a more thorough understanding of the present application and to enable the scope of the present application to be fully conveyed to those skilled in the art. As mentioned throughout the specification and claims, "comprising" or "including" is an open term, which is interpreted to mean "including, but not limited to". The subsequent description in the specification is a preferred embodiment for implementing the present application, and is for the purpose of illustrating the general principles of the specification, and is not intended to limit the scope of the present application. The scope of protection of the present application is defined by the appended claims.

[0019] The application is a technology for controlling and inhibiting heavy metal enrichment of crops, and has important practical significance in safe utilization of Cd-polluted farmland.

[0020] The method of the application comprises the following specific steps: (1) rice husks are washed twice with distilled water, dried, placed in a muffle furnace, and carbonized under anaerobic conditions at 700 DEG C for 5 hours, and then ground and sieved through a 100-mesh sieve to obtain the required biochar; (2) commercially available seedling nutrient soil is prepared by adding 4% of the biochar prepared in step (1) by mass, and the biochar and the seedling nutrient soil are thoroughly mixed and allowed to stand for 1 day, and then loaded into seedling pots (seedling nutrient pots with a depth of 13 cm and a diameter of 9 cm); (3) Solanum torvum seeds are sown in the seedling plug trays of step (2) for seedling, and common tomatoes are sown according to the conventional method (without adding biochar), with 1 seedling per seedling pot, and the Solanum torvum seeds are sown 30 days earlier than the tomatoes; (4) when the Solanum torvum seedlings grow to 5-6 leaf stages and the tomato seedlings are at the cotyledon stage, the Solanum torvum is used as a stock and the tomato is used as a scion, and the grafting is performed by using the wedge grafting method: a sterilized knife is used to cut the Solanum torvum seedling horizontally at a position 2 cm above the root of the 2nd leaf, and a cut of about 1.0 cm deep is made at the top of the cut stem; the tomato seedling is cut horizontally at a position 2 cm below the 1st pair of true leaves, and the bottom of the cut stem is trimmed into a wedge shape and inserted into the cut of the Solanum torvum seedling, so that the grafting point is tightly combined, and a grafting clamp is used for fixation; (5) the grafted tomato seedlings are placed in a black light-shielded shed, and are completely shielded from light for 1-5 days, and the ground is watered to make the air humidity reach more than 95%; the seedlings are half-shielded from light for 6-10 days, and the ventilation time is increased, and the air humidity is maintained at about 70%; the seedlings are placed in a natural environment for hardening for 11-15 days; after hardening, the grafted tomato seedlings in each hole, together with the biochar-containing seedling nutrient soil wrapped around the root system, are transplanted into the Cd-polluted farmland soil, and the conventional field management measures are implemented, so that the Cd content in the tomato fruits can be significantly reduced.

[0021] Example 1 A seedling and cultivation method for synergistically reducing the cadmium content in tomato fruits comprises the following steps: (1) Preparation of biochar: take rice husk, wash it with distilled water for 2 times, dry it and then put it in a muffle furnace under anaerobic conditions at 700℃ for 5 hours. After carbonization, it is naturally cooled to room temperature, ground and sieved through a 100 mesh sieve to obtain the desired biochar.

[0022] (2) Preparation of biochar-containing seedling nutrient soil: take commercial seedling nutrient soil, add 4% of the prepared biochar in step (1) by mass, mix the biochar and seedling nutrient soil thoroughly, and then place it in a seedling pot (use a seedling nutrient pot with a depth of 13 cm and a diameter of 9 cm) after 1 day of standing. (3) Seedling raising: sow Torubam seeds in biochar-containing seedling plug trays for seedling raising, and raise common tomatoes by the conventional method (without adding biochar). Each seedling pot contains 1 seedling, and Torubam seeds are sown 30 days earlier than tomatoes.

[0023] (4) Grafting: when the Torubam seedlings grow to 5-6 leaf age and the tomato seedlings are at the cotyledon stage, use Torubam as the stock and tomato as the scion to perform grafting by the wedge grafting method: use a sterilized knife to cut the Torubam seedling horizontally at 2 cm above the root of the 2nd leaf, and cut a 1.0 cm deep notch downward at the top of the cut stem; cut the tomato seedling horizontally at 2 cm below the 1st pair of true leaves at the top, and cut the bottom of the cut stem into a wedge shape to be inserted into the notch of the Torubam seedling, so that the grafting point is tightly combined, and then use a grafting clamp to fix it; place the grafted tomato seedling in a black light-shielded shed, completely shield the light for 1-5 days, pour water on the ground to make the air humidity reach more than 95%, half-shield the light for 6-10 days, increase the ventilation time, and keep the air humidity at about 70%, and then place it in the natural environment for hardening-off for 11-15 days.

[0024] (5) Field test: the Cd-contaminated farmland is located in Zhangshi sewage irrigation area of Shenyang City, Liaoning Province (41°39'N, 123°02'E), and the total Cd concentration of the soil is 3.16±0.32 mg kg -1 (dry weight). After hardening-off Figure 1 , each hole is transplanted with grafted tomato seedlings, together with the biochar-containing seedling nutrient soil wrapped around the roots, to the Cd-contaminated farmland soil, and the conventional field management measures are implemented.

[0025] (6) Comparative test: on the basis of step (5), set up 2 comparative treatments: ① grafted tomatoes without adding biochar; ② add 3% (mass ratio of farmland soil) of biochar in the original contaminated soil according to the method of the current conventional biochar fixation technology (Wood, Z. H., Huang, Z. Z., et al. Effects of modified biochar on cadmium accumulation in pakchoi. Journal of Ecology and Rural Environment, 2025, 41(08): 1086-1094.). At the same time, use untreated tomato plants as a control (CK).

[0026] (7) Analysis of Cd content in tomato fruits: After ripening, grafted tomato and ungrafted tomato fruits were collected, dried at 75°C to constant weight, and 0.5 g of the sample was weighed into a high-pressure digestion tank for microwave digestion. The Cd content of the sample was determined by inductively coupled plasma mass spectrometry (ICP-MS), as shown in Table 1.

[0027] Table 1 Comparison of Cd content in grafted tomato and ungrafted tomato fruits in Cd-contaminated soil , As can be seen from Table 1, in the Cd-contaminated soil, compared with the control, the Cd content in the scion tomato fruits was reduced by 85.53% by the combination of biochar and grafting technology of the application, which was higher than 71.07% by the single use of grafting treatment technology (Table 1 single grafting) and 42.62% by the conventional biochar fixation technology (Table 1 conventional biochar fixation technology). -1 According to the National Food Safety Standard Limits of Contaminants in Foods (GB 2762), the limit value of cadmium (calculated as Cd) in fresh tomatoes is 0.05 mg / kg -1 As can be seen in the examples, only the application meets the food safety standards. In addition, compared with the conventional biochar fixation technology (adding biochar at 3% of the quality of arable land soil) in Table 1, the application (adding biochar at 4% of the quality of the seedling nutrient soil) significantly reduces the amount of biochar used, has little disturbance to the arable land soil environment, and has the effect of reducing costs and increasing efficiency.

[0028] Further, the BCR sequential extraction method was used to analyze the effective state content of Cd in the rhizosphere soil of tomatoes treated by the application (biochar combined with grafting) and the conventional biochar fixation technology in Table 1, and the results are shown in Table 2. As can be seen, compared with the application (biochar combined with grafting), the application transplants the grafted tomato seedlings together with the biochar-containing seedling nutrient soil into the Cd-contaminated arable land soil, and the biochar also plays a significant role in fixing Cd in the rhizosphere soil of tomatoes (significantly reducing the effective state Cd content). This may be because the biochar is relatively stable in the soil and always remains in the rhizosphere environment, while the amount of Cd absorbed by crops mainly depends on the content of the effective state Cd in the rhizosphere soil.

[0029] Table 2 Comparison of effective state Cd content in the rhizosphere soil of tomatoes under different treatments (mg / kg -1 ) , On the basis of the above tests, the growth and nutritional indicators of tomatoes under different treatments were determined, as shown in Table 3. As can be seen, the biochar combined with grafting technology used in the application does not have adverse effects on the quality and yield of tomato fruits.

[0030] Table 3 Comparison of partial growth indicators and nutrient indicators of tomatoes under different treatments , From the above cases, the biochar combined grafting technology has a significant synergistic cadmium reduction effect, is a simple, green, low-cost and low-technology requirement technology, and provides a new way for safe use of heavy metal Cd contaminated farmland.

[0031] It can be understood that the above specific description of the present application is only used to illustrate the present application and is not limited to the technical solutions described in the embodiments of the present application. It should be understood by those skilled in the art that the present application can still be modified or replaced equivalently to achieve the same technical effect; as long as the use needs are met, it is within the protection scope of the present application.

Claims

1. A method of seedling raising and cultivation for synergistically reducing cadmium content in tomato fruits, characterized by, The method comprises the following steps: (1) mixing biochar with seedling nutrient soil to obtain biochar-containing seedling substrate; (2) seedling culture in the biochar-containing seedling substrate of step (1) with Toru Babam as stock; (3) seedling culture with tomato as scion; (4) grafting the tomato scion of step (3) onto the Toru Babam stock of step (2) to obtain grafted seedlings; (5) transplanting the grafted seedlings of step (4) together with the biochar-containing seedling substrate of the roots thereof into cadmium-contaminated soil for cultivation.

2. The method for raising seedlings and cultivating to reduce cadmium content in tomato fruits synergistically according to claim 1, characterized by, The biochar is prepared by pyrolysis of biomass waste under high-temperature anaerobic conditions.

3. The method for raising seedlings and cultivating to reduce cadmium content in tomato fruits synergistically according to claim 2, characterized by, The biochar is rice husk biochar, and the pyrolysis temperature is 600-800℃.

4. The method for raising seedlings and cultivating, which synergistically reduces cadmium content in tomato fruits according to claim 1, characterized by, In step (1), the addition amount of the biochar is 2-5% of the mass of the seedling nutrient soil.

5. The method for raising seedlings and cultivating, which synergistically reduces cadmium content in tomato fruits according to claim 4, characterized by, In step (2), the sowing time of the Toru Babam is 25-35 days earlier than that of the tomato.

6. The method for raising seedlings and cultivating, which synergistically reduces cadmium content in tomato fruits according to claim 5, characterized by, In step (4), the grafting is performed by wedge grafting when the Toru Babam stock grows to 5-6 leaf ages and the tomato scion is at the cotyledon stage to the two-true-leaf stage.

7. The method for raising seedlings and cultivating, which synergistically reduces cadmium content in tomato fruits according to claim 6, characterized by, In step (5), the grafted seedlings of step (4) are subjected to hardening treatment before transplanting, and the hardening treatment comprises culturing in a light-shielded and high-humidity environment for 1-15 days.

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