CN107836303B

CN107836303B - Cadmium-polluted farmland safe utilization method based on multifunctional crop sweet sorghum

Info

Publication number: CN107836303B
Application number: CN201710569552.8A
Authority: CN
Inventors: 李十中; 李纪红; 薛忠财; 仉磊
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2017-07-13
Filing date: 2017-07-13
Publication date: 2020-05-22
Anticipated expiration: 2037-07-13
Also published as: CN107836303A

Abstract

The invention provides a cadmium-polluted farmland safe utilization method based on a multifunctional crop sweet sorghum, which is characterized in that sweet sorghum of different varieties is planted on a cadmium-polluted farmland, and the most suitable sweet sorghum variety is selected by comparing and analyzing the distribution condition of cadmium absorbed by the sweet sorghum, so that the cadmium-polluted farmland is safely utilized, certain economic benefit is generated, the economic benefit problem of heavy metal-polluted land treatment is solved, the planting area of the multifunctional crop can be effectively enlarged, cadmium in soil is effectively extracted and separated, and the purpose of changing and repairing while production is really realized. The method has simple and convenient technology and easy method, and has extremely wide application prospect in wide cadmium-polluted areas.

Description

Cadmium-polluted farmland safe utilization method based on multifunctional crop sweet sorghum

Technical Field

The invention relates to the field of environment restoration of heavy metal polluted farmlands, in particular to a method for realizing safe utilization of cadmium polluted farmlands by utilizing a multifunctional crop, namely sweet sorghum, and belongs to the technical field of environmental pollution treatment and new energy.

Background

Soil is the material foundation on which humans rely for survival. However, the national soil pollution status survey bulletin (2014) published by the ministry of environmental protection and the ministry of homeland resources showed that: the soil pollution problem in China is very serious, the total standard exceeding rate is 16.1%, wherein the standard exceeding problem of cadmium is the most serious, the standard exceeding point reaches 7.0%, and the main sources are as follows: the discharge of industrial three wastes, the irrigation of sewage in agriculture, the application of sludge and phosphate fertilizer, and the like. Cadmium is easily absorbed by plants, so that the cadmium enters a food chain and threatens human health, therefore, the cadmium-polluted farmland has the characteristics of concealment, long-term property, irreversibility and the like, however, in combination with the national conditions of more people and less land in China, the cadmium-polluted farmland cannot be simply subjected to means of abandoned tillage repair and the like, and therefore how to utilize or repair the cadmium-polluted farmland and realize sustainable utilization of the polluted land are the problems which need to be solved urgently.

Although there are many methods for repairing heavy metal contaminated soil, including physical methods, chemical methods, biological methods and various technical combination methods, the physical methods and the chemical methods are often characterized by high repair cost, great damage to soil vegetation, serious secondary pollution and the like, and are mainly suitable for repairing small-area contaminated soil, and the application of the method in repairing large-area heavy metal contaminated farmlands is restricted. Compared with physical methods and chemical methods, although phytoremediation has the advantages of low cost, environmental friendliness, no secondary pollution, no damage to soil structures and the like, the defects of long phytoremediation period, low remediation efficiency, low economic benefit and the like seriously restrict the popularization and application of phytoremediation.

Therefore, aiming at the cadmium-polluted farmland, two aspects of grain safety and economic benefit need to be considered simultaneously, the produced agricultural products containing heavy metal pollutants are prevented from entering a food chain, and the economic output of the farmland is ensured.

Sweet Sorghum (Sorghum bicolor (Linn.) Moench) as an important energy plant and grain crop has the characteristics of high photosynthetic efficiency, high biological yield, strong stress resistance, wide adaptability and the like, has strong absorption capacity and tolerance to heavy metals such as zinc, arsenic, copper, cadmium and the like, and can produce 5-6 tons of stalks containing 12-14% of sugar per mu. Therefore, the production of ethanol by sweet sorghum is considered to be one of the most potential alternative petroleum ways, and has the advantages of mature fermentation process, short production period and relatively low production cost.

Therefore, a safe utilization method of the cadmium-polluted farmland based on the sweet sorghum, which can restore the cadmium-polluted farmland, realize effective cadmium recovery and bring certain economic benefits, is needed.

Disclosure of Invention

In order to solve the problems, the invention aims to provide a safe and economic utilization method of cadmium-polluted farmland based on multifunctional crop sweet sorghum, which comprises the following steps:

the method comprises the following steps: planting a multifunctional crop sweet sorghum in a cadmium-polluted farmland, effectively absorbing heavy metal cadmium in soil, and repairing the soil; the variety for planting the sweet sorghum is N31F 2087.

Step two: planting the sweet sorghum by adopting proper cultivation management measures to ensure the normal growth of the sweet sorghum;

step three: harvesting overground parts after the seeds are mature, and using the sweet sorghum seeds for eating or feeding;

step four: sweet sorghum stalks are used as raw materials for producing ethanol by a solid state fermentation technology, and heavy metal cadmium is recovered by combusting fermentation residues, so that cadmium in soil is prevented from entering a food chain.

In the first step, planting the energy plant sweet sorghum in the cadmium-polluted farmland. The different varieties of the sweet sorghum have different absorption characteristics to cadmium, and the variety of the sweet sorghum with high accumulation amount and large biomass is selected.

Preferably, the variety of the sweet sorghum is N31F2087, and is obtained by analyzing the genetic germplasm resources of the sweet sorghum: the sweet sorghum has large biomass, can absorb heavy metal cadmium to the maximum extent, and has the lowest content of heavy metal cadmium in grains. Generally, the cadmium content in the N31F2087 stalks reaches 2.60mg/kg, the cadmium content in the seeds is less than 0.02mg/kg, and the cadmium content is far lower than 0.1mg/kg of the grain pollutant detection standard (GB-2762-2012). If the weight of the dry N31F2087 is 270g per plant, the cadmium content in the stalks reaches 2.60mg/kg, and each plant can absorb 702 mu g of cadmium.

In the second step, proper cultivation management measures are adopted to ensure the normal growth of the sweet sorghum.

Preferably, planting sweet sorghum with appropriate management measures comprises the following steps:

and (3) planting in the early stage: 1. deep ploughing and fine cropping: deep ploughing is used for creating a loose soil layer, improving the soil fertility and heat condition, and facilitating the extension of root systems and the activity of soil microorganisms; preferably, the plowing depth is 30-35 cm.

2. Herbicide treatment: used as indicated.

3. Applying a base fertilizer: 20-25 kg of urea and 20-25 kg of diammonium phosphate.

And (3) sowing time: precision dibbling, preferably, the planting density is 0.2m multiplied by 0.5 m; the sowing depth is 3-4 cm; 2-3 seeds per hole, 0.8-1 kg seeding amount per mu.

Thinning and fixing period: preferably, thinning is performed at a 2-3 leaf stage; and (4) performing final singling in a leaf stage of 4-5, and reserving one strain in each hole.

And (3) water and fertilizer management in a seedling stage: and in the seedling stage, head water is poured in due time according to the rainfall condition, the soil moisture content and the plant growth vigor.

Preferably, 10-15 kg of ammonium sulfate is applied in combination with watering per mu in the booting stage for improving the content of effective cadmium in the soil.

And (3) pest control from a seedling stage to a mature plant stage: firstly, prevention and control of aphids: 30-90g of 10% imidacloprid wettable powder is respectively used per mu from the seedling stage to the adult stage. 20-60ml of 3% abamectin high-chlorine emulsifiable concentrate and 10-30ml of 40% chlorpyrifos emulsifiable concentrate, and according to the plant size, one kind of medicament is optionally mixed with 30-90 kg of water to spray leaf surfaces. The sugar content of the sweet sorghum is high, the sweet sorghum is easily damaged by aphids, the key period for preventing and controlling the aphids is in the middle and last 7 months, and the aphids are easily heavier and should be prevented and controlled as soon as possible in the weather of high temperature and drought and less rainfall. Secondly, prevention and treatment of red spiders: in seedling stage and adult stage, 1.8% avermectin emulsion 15-30ml, 73% propargite emulsion 15-45ml and 30-90 kg of water are added to each mu of leaf surface for spraying control. The insect pests are mainly released on the back of the leaves, and the damage degree is less than that of the corn.

And (3) harvesting period: harvesting timely according to the growth condition of the sweet sorghum.

In the second step, the cultivation management measures can improve the content of the available cadmium in the soil by applying ammonium sulfate to the soil in the booting stage, so that the absorption amount of heavy metals by the overground part of the sweet sorghum is improved, and the repair efficiency of the sweet sorghum is further improved.

In the third step, after the sweet sorghum is mature, the overground part is harvested to obtain raw material stalks produced by the solid fermentation technology and grains meeting the national food standard.

Harvesting overground parts of the sweet sorghum, wherein the stalks can absorb heavy metal cadmium in soil to the maximum extent to achieve the effect of repairing the soil, and the stalks absorbing the heavy metal are used for producing ethanol with economic value through a solid state fermentation technology; the cadmium content in the grains is extremely low, the grains meet the detection standard (GB-2762-.

In the fourth step, sweet sorghum stalks are used as raw materials for producing ethanol by a solid state fermentation technology, and the fermentation residues are combusted to produce heat or electricity, and simultaneously heavy metal cadmium is recovered. The solid-state fermentation technology is ASSF continuous solid-state fermentation, preservative is not used in the ASSF continuous solid-state fermentation, straw squeezing is not involved, no waste water is discharged, and a self-control continuous solid-state fermentation device is adopted to realize the continuity and automation of the solid-state fermentation process; the rotating speed of the fermentation tank body and the angle of the distributing plate are adjustable, so that the adjustable controllability of production is enhanced.

The strain used in the ASSF continuous solid state fermentation is Saccharomyces cerevisiae TSH2 with the preservation number: CGMCC 14223, wherein the preservation unit is China general microbiological culture Collection center (CGMCC), and the preservation date is 06 months (06 days) in 2017; the saccharomyces cerevisiae TSH2 is a special strain which is specially domesticated and genetically modified, can endure high temperature under the solid fermentation condition, and has high efficiency in absorbing fermentable sugar, so that the solid fermentation efficiency is obviously higher than that of other industrial yeasts, the fermentation time is shortened from 24h in the prior art to 20h, the strain is a high-yield ethanol yeast strain, and the problems of fermentation heat accumulation (high temperature) and poor mass transfer effect of the conventional strain on solid fermentation are effectively solved.

Compared with the prior art, the invention has the following advantages:

1. aiming at the farmland with cadmium pollution, the invention changes the agricultural planting structure, plants the sweet sorghum which is a resistant energy plant, screens out the most suitable sweet sorghum variety on the basis of the prior art, uses the stalks thereof for producing ethanol, uses the grains thereof for eating or feeding, and further improves the economic value of the produced plant.

2. The method adopts an advanced solid state fermentation technology to treat the sweet sorghum stalks rich in heavy metals, wherein the adopted strains are special saccharomyces cerevisiae strains, and the fermentation time is reduced from the original 24 hours to 20 hours.

3. The sweet sorghum planted can repair cadmium-polluted soil, and compared with the traditional repair method, the method has the advantages of low cost, environmental friendliness, no secondary pollution, no damage to the soil structure, and certain economic benefit, and really realizes the production-while-repair of cadmium-polluted farmlands.

4. The method has simple and convenient technology and easy operation, and has extremely wide application prospect in wide cadmium-polluted areas.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Detailed Description

The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.

Example 1 potting test

The test plants: sweet sorghum variety Pi5260601SDUSA

Test soil: taking farmland soil, naturally drying, removing impurities, grinding, sieving by a 6mm sieve, preparing cadmium contaminated soil according to the concentrations of 0, 1, 10 and 30mg/kg, and adding the same nitrogen, phosphorus and potassium base fertilizers, wherein the dosages are respectively as follows: 200mg/Kg of nitrogenous fertilizer, 100mg/Kg of phosphate fertilizer and 200mg/Kg of potash fertilizer are put into a flowerpot with the capacity of 7Kg, water is added for balancing for 30 days, and then the water content of the cultivated soil is maintained at 70 percent of the field water holding capacity (70 percent is the optimal field water content for the growth of dry land plants). And (3) selecting sweet sorghum seedlings with consistent growth for transplanting, planting 1 sweet sorghum seedling in each pot, repeating 6 pots for each treatment, performing normal water and fertilizer management in the period, and harvesting the overground part of the sweet sorghum after the sweet sorghum is mature.

And (5) measuring the cadmium content of different parts of the sweet sorghum. After harvesting of sweet sorghum, the sorghum was soaked for 3 hours with 20mM disodium ethylenediaminetetraacetate to remove surface-adhering ions, roots, stems, leaves and seeds were separated, washed 3-4 times with deionized water, the samples were blanched at 105 ℃ for 30min, then dried to constant weight at 80 ℃ and weighed, respectively, and the results are shown in Table 1, and then the samples were pulverized, digested with concentrated nitric acid, and cadmium content in the samples was measured by ICP-MS (Agilent 7700X, Agilent Technologies, USA), and the results are shown in Table 2.

TABLE 1 Dry weight of root, stem, leaf and kernel of sorghum saccharatum under various cadmium treatment conditions

Cadmium treatment/mg kg^-1	Root weight (g)	Stem weight (g)	Leaf weight (g)	Seed weight (g)
					0	11.89±4.98	34.55±3.54	20.98±3.08	2.83±0.36
1	13.75±3.46	32.80±3.96	22.37±3.92	2.76±0.27
					10	9.86±3.35	27.16±2.77	18.49±2.04	2.46±0.52
30	7.27±2.28	23.43±2.56	14.77±6.40	2.73±0.23

As can be seen from Table 1, the low concentration cadmium treatment (10mg/kg) has no effect on the growth of sweet sorghum, and under the high concentration cadmium treatment (30mg/kg), the growth of sweet sorghum is obviously inhibited, the weight of roots, stems and leaves is respectively reduced by 38.86%, 32.19% and 29.60% compared with the control, and the yield of grains is not affected.

TABLE 2 cadmium content in sweet sorghum fractions under different cadmium treatment conditions

As can be seen from Table 2: with the increase of the treatment concentration, the cadmium content in the roots, stems and leaves is gradually increased, and the cadmium content is characterized in that the roots, the stems, the leaves and the seeds are distributed in the sweet sorghum body. Under the treatment condition that the concentration of cadmium is 30mg/kg, the accumulation amounts of the stems, leaves and seeds of the overground parts of the sweet sorghum are 184.40 mu g/plant, 65.53 mu g/plant and 0.72 mu g/plant respectively. Although the growth of sweet sorghum is inhibited to some extent under the condition of high-concentration cadmium treatment (30mg/kg), the growth can be completed in a normal growth period and a certain yield can be achieved.

Furthermore, under the condition that the total cadmium content of the soil is certain, chemical medicines are added into the soil, the physical and chemical properties of the soil can be changed, the effective cadmium content in the soil is improved, the absorption capacity of heavy metals on the overground part of the sweet sorghum is further improved, and the repairing efficiency of the sweet sorghum is further improved. The chemical added is ammonium sulfate, and the ammonium sulfate is applied to the soil in the booting stage, so that nutrition is provided for the sweet sorghum, the plant growth is promoted, the bioavailability of cadmium in the soil can be improved, and the absorption of the sweet sorghum to the cadmium is facilitated. Heavy metal elements in soil mainly exist in five forms of a water-soluble state, an exchange state, a ferro-manganese oxide combined state, an organic combined state, a residue state and the like, the chemical activity and the physiological toxicity of heavy metals in various forms are different, main factors influencing the effectiveness of the heavy metals comprise a plurality of factors such as the pH value of the soil, the content of organic matters and the composition of humic acid, and the content of cadmium in the effective state is obviously increased along with the increase of the total content of cadmium in the soil.

Example 2 field planting test-Guangdong Shaoshaoguan

The method of the invention performs the trial planting on the heavy metal polluted farmland (the basic physical and chemical properties of the soil are shown in the table 3) in Shaoguan city, Guangdong province, and the cadmium content in the soil is 7.93 times higher than the national third-level soil standard value (1mg/kg) as can be seen from the table 3. 5 different sweet sorghum varieties (lines) are selected as materials in the test, and the method mainly comprises the following steps: N31F2087, 407A × late-maturing Nanpi, N32F2026, 823 and N31K 2168.

After the sweet sorghum is ripe, the plant height is measured, leaves are removed, stems and seeds are harvested respectively, the fresh weight of the stems is weighed, the samples are subjected to enzyme deactivation for 30min at 105 ℃, then the samples are dried to constant weight at 80 ℃, the dry weight is weighed, the water content of the stems is calculated, the dried stems and seeds are ground by a stainless steel grinder, then the stems and seeds are digested by concentrated nitric acid respectively, and the cadmium content in the samples is measured by ICP-MS (Agilent 7700X, Agilent Technologies, USA), and the results are shown in Table 4.

TABLE 3 basic physicochemical Properties of soil of test plot

pH	Organic matter/g.kg^-1	Quick-acting nitrogen/mg.kg^-1	Quick-acting phosphorus/mg.kg^-1	Quick-acting potassium/mg.kg^-1	Cadmium content/mg kg^-1
						5.97	42.25	267.65	20.59	100.5	7.93

TABLE 4 growth conditions of sweet sorghum of different varieties (lines) growing in cadmium-polluted farmland of Shaoyuan city, Guangdong province, and cadmium contents in stalks and grains

As can be seen from Table 4, the growth conditions of different varieties in the same place are obviously different, and the sweet sorghum stalks can be produced by 5.1-5.8t per mu according to 7000 plants planted per mu, the average yield per mu can be 5.5t, the average sugar content in the stalks is 10.03%, and the sugar can be produced by 550kg per mu. The sweet sorghum is planted in a cadmium-polluted farmland, the overground part of the sweet sorghum absorbs a part of cadmium, and different sweet sorghum varieties have different absorption amounts of cadmium, wherein the cadmium content in N31F2087 stems is 2.60mg/kg, compared with super-accumulation plants, the cadmium concentration in the sweet sorghum stems is lower, but the biomass is higher, the dry matter amount of N31F2087 is 272.88 g/plant, each plant can absorb 709.4 mu g of cadmium, and the cadmium can be absorbed by the sweet sorghum stems per mu of 4966 mg/mu according to 7000 plants per mu.

According to results of field tests, the height of the sweet sorghum can reach 2.8-3.7m, cadmium content in grains reaches 0.1mg/kg of grain pollutant detection standard (GB-2762-. Wherein N31F2087 is the most suitable planting variety, the cadmium content of the stems is the highest, the cadmium content of the grains is the lowest, and the seeds are the safest.

Example 3 field planting test-Hunan Xiangtan

The method of the invention performs the seed test in the heavy metal polluted farmland (the basic physicochemical properties of the soil are shown in Table 5) in Hunan Tan City of Hunan province, and the cadmium content in the soil is 1.83 times higher than the standard value (0.3mg/kg) of the national second-level soil as can be seen from Table 5.5 different sweet sorghum varieties (lines) are selected as materials in the test, and the method mainly comprises the following steps: N31F2087, 407A × late-maturing Nanpi, N32F2026, 823 and N31K 2168.

After the sweet sorghum is ripe, the plant height is measured, leaves are removed, stems and seeds are harvested respectively, the fresh weight of the stems is weighed, the samples are subjected to enzyme deactivation for 30min at 105 ℃, then the samples are dried to constant weight at 80 ℃, the dry weight is weighed, the water content of the stems is calculated, the dried stems and seeds are ground by a stainless steel grinder, then the stems and seeds are digested by concentrated nitric acid respectively, and the cadmium content in the samples is measured by ICP-MS (Agilent 7700X, Agilent Technologies, USA), and the results are shown in Table 6.

TABLE 5 basic physicochemical Properties of soil of test plot

pH	Organic matter/g.kg^-1	Quick-acting nitrogen/mg.kg^-1	Quick-acting phosphorus/mg.kg^-1	Quick-acting potassium/mg.kg^-1	Cadmium content/mg kg^-1
						4.67	32	91	3.48	55	0.55

TABLE 6 growth conditions of different varieties (lines) of sweet sorghum growing in cadmium-polluted farmland of Hunan Tan City, Hunan province, and cadmium contents in stems and grains

As can be seen from Table 6, the growth conditions of different varieties in the same place are obviously different, and the sweet sorghum stalks can be produced by 5.1-6.0t per mu according to 7000 plants planted per mu, the average yield per mu can be 5.5t, the average sugar content in the stalks is 10.45%, and the sugar can be produced by 580kg per mu.

The sweet sorghum is planted in a cadmium-polluted farmland, the overground part of the sweet sorghum can absorb a part of cadmium, different sweet sorghum varieties have different absorption amounts of cadmium, the cadmium content in N31F2087 stems is 1.92mg/kg, compared with super-accumulation plants, the cadmium concentration in the sweet sorghum stems is lower, but the biomass is higher, the dry matter amount of N31F2087 is 230.88 g/plant, therefore, each plant can absorb 443.28 mu g/plant of cadmium, and each mu of sweet sorghum stems can absorb 3103 mg/mu calculated according to 7000 plants per mu.

The height of the sweet sorghum planted in Hunan Tan cadmium-polluted farmland can reach 2.8-3.3m, and the cadmium content in grains reaches 0.1mg/kg of grain pollutant detection standard (GB-2762-.

Example 4 fermentation Using solid State fermentation technology

The fermentation objects are: sweet sorghum stalk of variety N31F2087

The adopted fermentation strains are as follows: specific Saccharomyces cerevisiae TSH2(Saccharomyces cerevisiae Hansen)

The method comprises the steps of peeling leaves of N31F2087 fresh sweet sorghum stalks rich in heavy metal cadmium, crushing, mixing uniformly (the diameter is 1-5mm, the length is less than 50mm), weighing 10kg of crushed materials, inoculating a cultured seed solution (a strain is Saccharomyces cerevisiae (TSH 2)) according to the inoculation amount of 10%, fermenting at the initial fermentation temperature of 25-35 ℃, putting the seeds into a 50L rotary drum type fermentation tank for fermentation, and controlling the stirring speed at 0.08rpm after fermenting for 20 h. Distilling to obtain ethanol with the ethanol yield of over 90 percent.

The strain adopted in the embodiment is obtained by screening, domesticating and genetic modification, and can tolerate high temperature under solid fermentation and has the characteristics of low mass transfer rate, so that the fermentation efficiency and the ethanol yield are improved, the fermentation time is reduced to 20 hours from the original 24 hours. The strain is saccharomyces cerevisiae TSH2, the preservation number is CGMCC 14223, and the preservation unit is as follows: the preservation date of the common microorganism center of China Committee for culture Collection of microorganisms is 2017, 06 months and 06 days.

According to the method, sweet sorghum of different varieties is planted on the cadmium-polluted farmland, the sweet sorghum variety which is most suitable for planting is selected, the safe utilization of the cadmium-polluted farmland is realized, certain economic benefit is generated, the economic benefit problem of polluted land treatment is solved, the planting area of energy plants can be effectively enlarged, cadmium in soil is restored, and the purpose of production-time remediation is really realized. The method has simple and convenient technology and easy method, and has extremely wide application prospect in wide cadmium-polluted areas.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A cadmium-polluted farmland safe utilization method based on multifunctional crop sweet sorghum comprises the following steps:

the method comprises the following steps: planting a multifunctional crop sweet sorghum on a cadmium-polluted farmland, wherein the variety of the planted sweet sorghum is N31F 2087;

step four: the sweet sorghum stalks are used as raw materials to produce ethanol by adopting a solid state fermentation technology, the heat produced by combusting fermentation residues is used for ethanol production and power generation or heat supply, and simultaneously heavy metal cadmium is recovered, so that the cadmium absorbed from soil is prevented from entering a food chain,

the solid-state fermentation technology is ASSF continuous solid-state fermentation, the used strain is Saccharomyces cerevisiae TSH2, the preservation number is CGMCC 14223, the preservation unit is China general microbiological culture Collection center, and the preservation date is 2017, 06 months and 06 days.

2. The safe utilization method of cadmium-polluted farmland as claimed in claim 1, wherein said cultivation management measures in the second step comprise the steps of:

and (3) planting in the early stage: deep ploughing and fine cultivating, wherein the ploughing depth is 30-35 cm;

applying a base fertilizer: 20-25 kg of urea and 20-25 kg of diammonium phosphate;

and (3) sowing time: precision dibbling, wherein the planting density is 0.2m multiplied by 0.5 m; the sowing depth is 3-4 cm; each hole has 2-3 grains, and the seeding quantity per mu is 0.8-1 kg;

thinning and fixing period: thinning is carried out in the period of 2-3 leaves; performing final singling in the leaf stage of 4-5, and reserving one strain in each hole;

watering the head water in the seedling stage according to the rainfall condition, the soil moisture content and the plant growth condition;

in the booting stage, 10-15 kg of ammonium sulfate is applied in combination with watering per mu for improving the content of effective cadmium in soil;

and (3) pest control from a seedling stage to a mature plant stage: and (3) prevention and control of aphids: in the period from seedling stage to adult plant stage, 30-90g of 10% imidacloprid wettable powder, 20-60ml of 3% abamectin high-chlorine emulsifiable concentrate and 10-30ml of 40% chlorpyrifos emulsifiable concentrate are respectively used for each mu, and one medicament is optionally added with 30-90 kg of water according to the size of the plant for foliage spraying; and (3) prevention and treatment of red spiders: in seedling stage and adult stage, 1.8% avermectin emulsion 15-30ml, 73% propargite emulsion 15-45ml and 30-90 kg of water are added to each mu of leaf surface for spraying control.

3. The safe utilization method for cadmium-contaminated farmland as claimed in claim 1, wherein said seeds in step three are used for food or feed.