Safe utilization method for managing and controlling agricultural cultivated land in north

Abstract

The controlled agricultural cultivated land is cultivated land with the soil heavy metal content higher than the national risk screening value. In order to improve the land utilization rate, the invention provides a safe utilization method suitable for managing and controlling the agricultural cultivated land in the north, and economic benefits of the land are increased while the polluted cultivated land is repaired. The invention relates to the field of agricultural cultivation, in particular to an intercropping planting method for selecting Oasis No.1 fungus grass and fresh corn in controlled agricultural cultivated land, which is characterized in that different agronomic regulation and control are assisted according to production requirements, and absorption of heavy metal cadmium by the Oasis No.1 and crops is regulated and controlled based on ecological niche complementation and root exudates action mechanisms among the crops; and efficient and safe utilization of the agricultural cultivated land is managed and controlled. Moreover, the growth cycle is reasonably and efficiently utilized, efficient utilization of light, heat, water, fertilizer and other resources is achieved, the unit area yield of cultivated land and the land equivalence ratio are increased, and the method also plays a positive supporting role in promoting agricultural income increase and animal husbandry development.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of safe utilization of cultivated land, and particularly relates to a method for safe utilization of cultivated land in the north, in particular to a method for safe planting of fresh corn and oasis No. 1 in a cadmium-polluted farmland. BACKGROUND

[0002] The controlled cultivated land refers to the cultivated land with a heavy metal content higher than the risk screening value in the "GB 15618-2018 Soil Environmental Quality of Agricultural Land Soil Pollution Risk Control Standard (Trial)".

[0003] The large population and small land area of China determines that the large-area contaminated farmland soil remediation cannot be carried out by completely interrupting agricultural production. The feasibility of safe utilization technology of contaminated farmland must consider the acceptance of farmers, the sustainability of agricultural production, the funding of beneficiaries and other issues. By adjusting the planting structure, planting non-edible economic crops, economic tree species and other heavy metals, and screening low-accumulation crop varieties, the contaminated farmland can be repaired while bringing considerable income to farmers, so as to mobilize the enthusiasm of farmers for agricultural remediation. However, due to the variability of soil physical and chemical structure, pollution source, climate condition and other factors, a single safe utilization technology has the disadvantages of low remediation efficiency and limited application range, and needs to be combined with the type and degree of cultivated land pollution to integrate multiple remediation technologies for joint repair, so as to establish an economic and efficient farmland safe utilization technology suitable for local conditions, and achieve the dual purpose of agricultural production and soil pollution remediation. The Chinese patent "A method for repairing heavy metal contaminated farmland" (application number: 202111080136.4) introduces a method for realizing safe utilization and remediation of contaminated farmland by regulating the absorption of oasis No. 1 to heavy metals. This method combines farmland remediation with safe utilization, but the yield of oasis No. 1 is small and the economic benefit is low in the early stage of planting.

[0004] Intercropping is a traditional agricultural utilization method to improve the soil equivalent ratio and increase yield and efficiency. The uptake of heavy metals by plants is selective, and intercropping can achieve the purpose of dispersing the absorption of soil heavy metals through the cooperation between different plants to jointly utilize soil nutrients and water. The interaction between plant roots in the intercropping system further changes the composition and proportion of low molecular weight organic acids secreted by the roots, and the enrichment plants inhibit the amount and type of low molecular weight organic acids secreted by crop roots, resulting in less heavy metals being activated in the soil, thereby reducing the absorption of heavy metals by intercropped plants. Moreover, based on the principles of niche complementation and biodiversity, the two crops during the symbiotic period can improve the effective use of resources by plants, while increasing the activity of some enzymes in the soil to improve the coexistence environment of soil microorganisms, thereby achieving the effects of increasing yield and quality. The leaf surface regulation technology can regulate the absorption, transport and accumulation of heavy metals in plants by spraying leaf surface regulators.

[0005] The category and variety of crops have a dual effect of promoting and inhibiting the growth of enrichment plants. Selecting appropriate plants to form an intercropping complex system can achieve the purpose of repairing and producing simultaneously in contaminated farmland, improve the repair efficiency and benefit, and is a new way of soil repair. At present, the main cadmium enrichment plants are Sedum alfredii Hance and Solanum nigrum L., which have the disadvantages of slow growth and small plant size, and are not suitable for intercropping with corn in the dry land of the north. Moreover, the subsequent treatment of enrichment plants mainly adopts the method of incineration, which is expensive and has low resource utilization. The Chinese patent "A method for intercropping corn and giant kang grass to repair cadmium-contaminated farmland" (application number: 202110473280.8) plants corn and giant kang grass in an intercropping manner, which realizes in-situ non-destructive "repair and production simultaneously" in medium and light acid cadmium-contaminated farmland (soil cadmium content of 0.30-0.75 mg / kg). The farmland repair technology has strong regional applicability and is only suitable for acid contaminated farmland in the south. Limited by the soil conditions, there is no suitable safe utilization technology for contaminated farmland in the north, especially for the control of heavy pollution farmland. Based on this, the present application is developed. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a safe utilization method for north control farmland, especially a safe agricultural planting method for cadmium-contaminated farmland. The method adopts low-accumulation crop varieties and non-edible economic plants for intercropping, supplemented by leaf surface regulation technology for joint repair, which reasonably regulates the transfer of heavy metals in different growth stages of plants, improves the land equivalent ratio, and increases the economic benefits of the safe utilization mode.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A safe utilization method of northern controlled agricultural land, comprising the following steps:

[0009] 1) Land consolidation: land is consolidated to the state of being ready for planting before planting; specifically, on the eve of planting, bottom fertilizer is applied to each mu of land, and mechanical plowing, harrowing and leveling are performed to make the land ready for planting; about a week before planting, land consolidation is performed for Oasis No. 1. Preferably, organic fertilizer or nitrogen, phosphorus and potassium compound fertilizer is applied as the bottom fertilizer for the controlled agricultural land. The amount of organic fertilizer applied is 300-400 kg per mu of land, and the amount of nitrogen, phosphorus and potassium compound fertilizer applied is 20-30 kg per mu of land, so as to ensure that the mass ratio of nitrogen: phosphorus: potassium is (13-16):(12-18):(11-15); water is applied at irregular intervals according to the soil moisture condition;

[0010] 2) Crop planting: Oasis No. 1 and fresh corn are planted by intercropping; the planting time of Oasis No. 1 is the end of March to the eve of Tomb-Sweeping Day, and the planting time of fresh corn is the middle and late period of April;

[0011] 3) Crop management: when Oasis No. 1 grows to 6 leaves and 1 heart, growth regulator GR-1 is sprayed; when corn grows to 6 leaves and 1 heart, growth regulator GR-2 is sprayed;

[0012] 4) Crop harvesting: each crop of Oasis No. 1 is harvested when it grows to a height of 1-1.2 meters, and the harvested grass is used as silage feed; when fresh corn enters the mature period in July (the best harvesting period is when the husk is yellow, the milk line disappears, or the husk is peeled off, and the kernel has a certain elasticity and white milk flows out when the kernel is squeezed), the mature corn ear is harvested in time and stored in a fresh-keeping freezer; after the fresh corn ear is harvested, the corn stalks are harvested and crushed by a machine, and used as feed grass or organic fertilizer raw material;

[0013] 5) Dry grass management and harvesting of Oasis No. 1: after the fresh corn is harvested, growth regulator GR-3 is sprayed when Oasis No. 1 grows to 6 leaves and 1 heart; growth regulator GR-3 is sprayed again when Oasis No. 1 grows to a height of 1.0-1.5 meters, and attention is paid to the soil moisture condition in the middle; around January of the second year, dry grass of Oasis No. 1 is harvested and used as fiber extraction raw material.

[0014] Specifically, the above-mentioned safe utilization method of northern controlled agricultural land further comprises the following steps: after the dry grass of Oasis No. 1 is harvested, the land is harrowed and stubble is crushed, and the residual stems and leaves in the land are shallowly plowed into the soil as green manure; fresh corn is continuously intercropped in the spring of the second year, and Oasis No. 1 is regularly harvested to repeat a new round of intercropping, which is repeated 1-3 times.

[0015] Further, the oasis No. 1 can adopt the method of root cutting or tender seedling planting, and the plant spacing is 50-90 cm, the row spacing is 0.9-1.5 m, and the planting depth is 10-20 cm; irrigation is carried out for soil conservation within 1-2 days after planting. The planting density is about 800-1100 plants per mu.

[0016] During the growth of fresh corn, attention should be paid to weed management, especially after entering the rainy season. When spraying herbicides, attention should be paid to directional spraying, and the leaves and roots of oasis No. 1 should not be sprayed.

[0017] Specifically, in the above-mentioned method for safe use of the controlled farmland in the north, the cadmium content of the controlled farmland is not more than 10 mg / kg; when the cadmium content of the controlled farmland is 2.0-5.4 mg / kg, an intercropping mode of planting one row of oasis No. 1 and one row of corn is adopted, and the row spacing between two rows of oasis No. 1 is 0.9-1.3 m; when the cadmium content of the controlled farmland is 5.4-10 mg / kg, an intercropping mode of planting one row of oasis No. 1 and two rows of corn is adopted, and the row spacing between two rows of oasis No. 1 is 1.4-1.5 m. The corn is planted by dibbling or machine planting, one seed per hole, with a planting depth of 3.0-5.0 cm, a plant spacing of 30-40 cm, and fresh corn preferably Zhengnu 2000.

[0018] When the fresh corn grows to 8-12 leaves, it may have tillers, and preferably, the tillers are removed. When the fresh corn grows to the silking stage, preferably, 10±2 kg of nitrogen-phosphorus-potassium compound fertilizer can be applied per mu.

[0019] Further, during the intercropping planting in the first year, the oasis No. 1 is harvested as forage about 2 times, and the first harvesting time is two months after planting forage, which is at the end of May or early June; after the second year, the oasis No. 1 can be harvested as forage 3-4 times, and the first harvesting time is early May, and after the first harvesting, it is harvested again every 20-25 days, and the stubble above ground is left 2-8 cm.

[0020] Further preferably, after each harvesting of oasis No. 1, 10-15 kg of nitrogen-phosphorus-potassium compound fertilizer is applied per mu, and irrigation is carried out in time to maintain the soil moisture.

[0021] The growth regulators GR-1 and GR-2 are applied by spraying, with a dosage of 100-400 g and 50-400 g per mu. When applied, they are diluted with water in a certain proportion, with a spraying amount of 10-30 kg per mu. The amino acid water-soluble fertilizer is a commercially available amino acid water-soluble fertilizer (powder type), preferably an amino acid trace element fertilizer, with a free amino acid content of ≥10.0%. The 2-(3,4-dichlorophenoxy) triethylamine is a commercially available chemical pure product, with a purity of ≥95%. The medium element water-soluble fertilizer is a commercially available medium element water-soluble fertilizer (powder type). When the growth regulators are sprayed, a suitable amount of surfactant can be added as an auxiliary agent, such as one or a mixture of two or more of sodium dodecylbenzenesulfonate, organosilicon, neohydrazide, polyethylene glycol, and Tween. The growth regulator GR-3 is applied by flushing, with a dosage of 200-900 g per mu, wherein the potassium polyacrylate has a molecular weight of 2000-4000 and a solid content of ≥40%.

[0022] Specifically, in step 3), the growth regulator GR-1 can be composed of 2-(3,4-dichlorophenoxy) triethylamine, organic zinc selenide polyacrylamide solution, and amino acid water-soluble fertilizer in a mass ratio of (1.5-8.0):(85-180):(20-70). When sprayed, it is diluted with water in a proportion of 50-200 times, with a dosage of 100-400 g per mu.

[0023] Specifically, in step 3), the growth regulator GR-2 can be composed of 2-(3,4-dichlorophenoxy) triethylamine, 15% uniconazole potassium liquid, and medium element water-soluble fertilizer in a mass ratio of (3.0-14):(9-16):(60-220). When sprayed, it is diluted with water in a proportion of 50-300 times, with a dosage of 50-400 g per mu.

[0024] Further, in step 5), the growth regulator GR-3 can be composed of 2-(3,4-dichlorophenoxy) triethylamine, ethylenediamine disuccinic acid, and potassium polyacrylate in a mass ratio of (1.0-6.0):(8-14):(20-50). When used, it is flushed with a dosage of 200-900 g per mu.

[0025] Further preferably, the organic zinc selenide polyacrylamide solution can be prepared by the following steps:

[0026] a) Preparation of organic zinc selenide colloidal solution: 130-170 g of sodium oleate is dissolved in 1 L of 20%-30% volume concentration of ethanol aqueous solution, then 10-15 g of zinc sulfate is continuously added under inert gas atmosphere, and fresh prepared NaHSe solution is continuously added during stirring, and stirring is continued for a certain time, so that the molar ratio of zinc to selenium is maintained at 3-5:1; the mixed solution is subjected to microwave reaction at 150-200 DEG C and 300-400 W for 30-60 min; after the reaction is completed, solid powder is obtained by centrifugation, and ultrasonic dispersion is performed with a volume ratio of 1:8-12 of mercaptopropionic acid-chloroform mixture, and organic zinc selenide colloidal solution is obtained by centrifugal separation;

[0027] b) Preparation of polyacrylamide solution: 10-60 g of ethyl acetate, 60 g of 9%-12% acrylamide monomer aqueous solution, 6 g of 3% ethylenediaminetetraacetic acid disodium aqueous solution and 2 g of 0.4%-2% ammonium persulfate solution are uniformly mixed, and gradually heated to reflux, and 230 g of 9%-12% acrylamide monomer aqueous solution and 18 g of 0.4%-2% ammonium persulfate solution are continuously added dropwise, and the dropwise addition is completed within 1-3 h, and the reaction is continued for 2 h after the dropwise addition is completed, and the mixture of ethyl acetate and water is distilled off under normal pressure, and the polyacrylamide solution with a solid content of 8%-12% and a molecular weight of 400-1000 kDa is obtained by cooling;

[0028] c) The organic zinc selenide colloidal solution, the polyacrylamide solution and water prepared above are mixed in a mass ratio of (0.8-1.2):(15-25):(75-100), and slight oscillation is performed for 6-8 h, to obtain the organic zinc selenide polyacrylamide solution.

[0029] The controlled agricultural land is the farmland with heavy metal content higher than the national risk screening value. In order to improve the land utilization rate, the application provides a safe utilization method suitable for the controlled agricultural land in the north, which can repair the contaminated farmland and increase the economic benefit of the land. Specifically, the application relates to a method for interplanting oasis No. 1 and fresh corn in the controlled agricultural land, and different agricultural controls are supplemented according to production requirements, and based on the niche complementation and root secretion mechanism between crops, the absorption of oasis No. 1 and agricultural products to cadmium is controlled, so that the efficient and safe utilization of the controlled agricultural land is realized. In addition, the growth cycle is reasonably and efficiently utilized, the efficient utilization of resources such as light, heat, water and fertilizer is realized, the unit area yield and land equivalent ratio of the farmland are improved, and the application also plays a positive supporting role in promoting agricultural income and the development of animal husbandry. Compared with the prior art, the method has the following advantages and beneficial effects:

[0030] 1) The application applies the intercropping technology of Oasis No. 1 and corn, the main grain crop in the north, to the control of agricultural land, effectively realizes the complementary advantages between varieties, improves the land output per unit area, obtains more agricultural income, and meets the development trend of modern agricultural production with high output, low energy consumption, and reduced use of fertilizers and pesticides.

[0031] 2) Spraying mineral elements such as selenium and zinc on the leaves can not only improve the quality of agricultural products by participating in the respiration and photosynthesis of plants, but also alleviate the toxicity of heavy metals to crops and regulate their accumulation in crops through the antagonism between mineral elements and heavy metals. In the application, the leaf regulator is a self-made organic zinc selenide polyacrylamide colloidal solution. Compared with conventional inorganic salt mineral elements, it has the characteristics of small particle size and good biocompatibility, and is more easily absorbed by plants. Moreover, the mercaptopropionic acid and polyacrylamide wrapped on the surface of the zinc selenide colloid can further chelate with free cadmium ions in cells through mercapto and carboxyl groups, reduce the concentration of free cadmium ions in cells, alleviate the toxicity of plants, and improve the growth and quality of plants, achieving multiple goals at once.

[0032] 3) The aqueous solution of polyacrylamide (molecular weight 400-1000 kDa) is gel-like and has an irregular network structure, which forms more complex hollow structures in the water absorption state, has good water retention effect, can reduce the leaching of fertilizers, and promote plant growth. Compared with small molecular weight polyacrylamide, the polyacrylamide used in the application has a larger molecular weight, and its gel molecules form more complex spatial structures, which have stronger fixing capacity for free cadmium ions.

[0033] 4) Ethylenediamine disuccinic acid, as a biodegradable chelating agent, can promote the absorption of heavy metals by plants from the soil. Combined with small molecular weight polyacrylate, it can utilize the water retention characteristics of polyacrylate, accelerate the transportation of heavy metal ions in plant stems and leaves based on transpiration, and improve the absorption of heavy metal ions by plants. In addition, small molecular weight polyacrylate not only can adsorb cadmium ions under aqueous conditions, but also can fix them and separate them from the soil solution. Compared with polyacrylate with a larger molecular weight, cadmium ions adsorbed on the surface of small molecular weight polyacrylate are more easily separated from the soil due to their weaker binding force.

[0034] 5) The use of growth regulators in the application improves the biomass of the intercropping system, ensures the quality and safety of the crops in the intercropping system, and improves the remediation efficiency of the planting mode.

[0035] 6)In the present application, No. 1 Oasis has the advantages of fast growth speed, high protein content, large biomass, mowing, long planting life, etc. Corn is a low-accumulation and strong-tolerance crop commonly used in the north. The growth periods of the two plants are different, so the intercropping combination of No. 1 Oasis and corn will not affect the absorption of light, water, fertilizer and other conditions by each other, and is suitable for safe use of polluted farmland in the north. Moreover, the method of the present application also alleviates the current situation of lack of forage grass in the north, avoids the forage of agricultural land, and has important significance in realizing the win-win of forage supply and soil remediation management in the north. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Fresh corn jointing stage and No. 1 Oasis intercropping planting growth status;

[0037] Figure 2 Fresh corn silking stage and No. 1 Oasis intercropping planting growth status;

[0038] Figure 3 Transmission electron microscope image of the prepared organic zinc selenide colloidal solution;

[0039] Figure 4 Transmission electron microscope image of the prepared polyacrylamide. DETAILED DESCRIPTION

[0040] The technical solutions of the present application are further described in detail below in combination with examples, but the protection scope of the present application is not limited thereto.

[0041] In the following examples, the raw materials or fertilizers used are ordinary commercially available products or can be prepared by conventional techniques in the art. For example, 2-(3,4-dichlorophenoxy) triethylamine is a commercially available chemical pure product with a purity of ≥95%. The potassium polyacrylate has a molecular weight of 2000-4000 and a solid content of ≥40%, which is an ordinary commercially available product purchased from Zhengzhou Kangning Technology Co., Ltd.

[0042] The amino acid water-soluble fertilizer is a commercially available amino acid water-soluble fertilizer (powder type), amino acid chelated multi-element No. 3, with a free amino acid content of ≥10.0%, purchased from Chengdu Huameng Biological Technology Co., Ltd.

[0043] 15% Uniconazole calcium powder liquid, purchased from Henan Miaohe Agricultural Co., Ltd.

[0044] The medium element water-soluble fertilizer is a commercially available medium element water-soluble fertilizer Wurunkang (granular type) with a calcium + magnesium content of ≥10.0%, purchased from Shifang City Jia Sheng Agricultural Technology Co., Ltd.

[0045] In the following examples, the organic zinc selenide polyacrylamide solution can be prepared by the following steps:

[0046] a) Preparation method of organic zinc selenide colloidal solution: 150 g of sodium oleate was dissolved in 1 L of 25% volume concentration of ethanol aqueous solution; then 13 g of zinc sulfate was continuously added under nitrogen atmosphere, and freshly prepared NaHSe solution was continuously added during rapid stirring, and stirring was continued for a certain time, so as to maintain the molar ratio of zinc to selenium at 4:1. The mixed solution was subjected to microwave reaction at 170℃ and 350W microwave power for 45 min. After the reaction was completed, a solid powder was obtained by centrifugation, and the solid powder was ultrasonically dispersed in a thiolpropanoic acid-chloroform mixture with a volume ratio of 1:10 for 60 min, and then centrifuged to obtain a thiolpropanoic acid-wrapped zinc selenide colloidal solution. The excess thiolpropanoic acid was removed by chloroform washing several times. Figure 3 The transmission electron micrograph of the organic zinc selenide colloidal solution is shown in FIG. 1. Figure 3 As can be seen from FIG. 1, the prepared organic zinc selenide colloidal solution has good dispersibility and high crystallinity, and the diameter size is 4.5-6.5 nm.

[0047] b) Preparation method of polyacrylamide solution: 25 g of ethyl acetate, 60 g of 10% acrylamide monomer aqueous solution, 6 g of 3% ethylenediaminetetraacetic acid disodium aqueous solution, and 2 g of 1.0% ammonium persulfate solution were mixed uniformly, and gradually heated to reflux, and then 230 g of 10% acrylamide monomer aqueous solution and 18 g of 1.0% ammonium persulfate solution were continuously added dropwise, and the dropwise addition was completed within 2 h. After the dropwise addition was completed, the reaction was continued for 2 h, and then the ethyl acetate and water mixture was evaporated under normal pressure, and the temperature was lowered to obtain a polyacrylamide solution with a solid content of 10% and a molecular weight of 610,000. Figure 4 The transmission electron micrograph of the polyacrylamide is shown in FIG. 2. Figure 4 As can be seen from FIG. 2, the polyacrylamide has a multi-layered porous structure, and the diameter of the pores is about 400-900 nm.

[0048] c) Preparation method of organic zinc selenide-polyacrylamide solution: the prepared organic zinc selenide colloidal solution, polyacrylamide solution, and water were mixed in a mass ratio of 1:22:100, and slightly oscillated for 7 h to obtain the product.

[0049] The "GB 15618-2018 Soil Environmental Quality Agricultural Soil Pollution Risk Control Standard (Trial)" stipulates the agricultural land pollution risk screening value and control value, which are shown in Table 1 below.

[0050] Table 1 Agricultural land quality control value Unit: mg / kg

[0051]

[0052] Examples 1-4

[0053] The test area selects a pipe-controlled farmland in the north of Henan Province, the soil pH value of which is 7.95, the total cadmium content is 2.6 mg / kg, and the farmland belongs to a medium cadmium pollution farmland and is marked as test farmland 1. The pipe-controlled farmland is repaired and utilized by adopting the method, and the specific process is as follows.

[0054] 1) Land consolidation: before planting in late March, the selected test farmland is consolidated, 25 kg of nitrogen-phosphorus-potassium (15:15:15) compound fertilizer is applied as base fertilizer per mu, and the farmland is mechanically ploughed, harrowed and leveled to the state of waiting for planting.

[0055] 2) Crop planting: after one week of land consolidation, Lvxian No. 1 and fresh corn are planted by intercropping. Lvxian No. 1 is planted by trenching and grafting with a row spacing of 1.0-1.3 meters (see Table 2 for specific details of each embodiment), a planting depth of 10-20 cm and a planting density of about 800-900 plants per mu. After planting, the soil moisture is maintained by irrigation. In mid-to-late April, when the soil temperature rises above 10℃, fresh corn Zhengnu 2000 is sown in the middle of every two rows of Lvxian No. 1, one seed per hole, with a sowing depth of 3.0-5.0 cm and a plant spacing of 30-40 cm.

[0056] 3) Crop management: when Lvxian No. 1 grows to 6 leaves and 1 heart, the leaf surface is sprayed with growth regulator GR-1; when corn grows to 6 leaves and 1 heart, the leaf surface is sprayed with regulator GR-2.

[0057] The growth regulator GR-1 is composed of 2-(3,4-dichlorophenoxy) triethylamine, organic zinc selenide polyacrylamide solution and amino acid aqueous fertilizer with a mass ratio of (1.5-8.0):(85-180):(20-70) (see Table 2 for specific ratio of each embodiment); when spraying, the dosage is 200 g per mu, and it is diluted with water at a ratio of 100 times for use, and it is sprayed on the leaf surface and root of Lvxian No. 1 during dilution. The growth regulator GR-2 is composed of 2-(3,4-dichlorophenoxy) triethylamine, 15% uniconazole calcium powder solution and medium element water-soluble fertilizer with a weight ratio of (3.0-14):(9-16):(60-220) (see Table 2 for specific ratio of each embodiment); when spraying, the dosage is 50 g per mu, and it is diluted with water at a ratio of 200 times for use. In order to strengthen the effect of leaf spraying, 1.5 ml of Tween-20 and 1.5 ml of PEG-400 can be added as leaf wetting agent per kilogram of spraying solution. In addition, nitrogen-phosphorus-potassium (15:15:15) compound fertilizer is applied at a rate of 10 kg per mu during the corn growing period. During the growth of fresh corn, attention should be paid to weed management, especially after the rainy season. When spraying herbicides, directional spraying is required to avoid spraying on the leaf surface and roots of Lvxian No. 1. Figure 1 and Figure 2 The growth conditions of fresh corn at the jointing stage and the silking stage and the intercropping planting of Lvxian No. 1 are given.

[0058] 4) Crop harvesting: when Oasis No. 1 grows to 1-1.2 meters high, harvest in time for silage feed, and sample for determination of cadmium content in the plant. After each harvest, 15 kg of nitrogen, phosphorus and potassium (15:15:15) compound fertilizer is applied per mu, and irrigation is carried out in time to maintain soil moisture. In the middle of July, fresh corn enters the mature stage, and mature corn ears are harvested in time, frozen and preserved, and samples are taken for detection of cadmium content in corn kernels. After the corn ears are harvested, the corn stalks are harvested and crushed by machine for use as forage, and samples are taken for detection of cadmium content in the stalks.

[0059] 5) Dry grass management and harvesting of Oasis No. 1: After corn harvesting, when the new Oasis No. 1 grows to 6 leaves and 1 heart, growth regulator GR-3 is applied. When Oasis No. 1 grows to 1.0-1.5 meters high, growth regulator GR-3 is applied again, and attention is paid to soil moisture in between. Around January of the second year, dry grass of Oasis No. 1 is harvested for use as raw material for long fiber extraction, etc. The growth regulator GR-3 is composed of 2-(3,4-dichlorophenoxy) triethylamine, ethylenediamine disuccinic acid and potassium polyacrylate in a mass ratio of (1.0-6.0):(8-14):(20-50) (see Table 2 for specific ratios in each example); the dosage is 300 g per mu.

[0060] 6) After the dry grass of Oasis No. 1 is harvested, the land is raked and the stubble is crushed, and the residual stems and leaves in the field are shallowly turned into the soil as green manure.

[0061] After one year of farmland remediation, the cadmium content in Test Farmland 1 was reduced to some extent. In the second year, Oasis No. 1 had vigorous tillering and increased single cluster of tender shoots. Sampling analysis showed that the cadmium content in the tender grass was 0.273-0.526 mg / kg, which did not exceed the safe limit of cadmium in forage. In order to reduce planting costs, growth regulator can not be applied. At the same time, it is possible that the narrow row spacing of Oasis No. 1 caused by excessive tillering will not be conducive to the planting of fresh corn. Therefore, whether to continue intercropping fresh corn can be selected according to the tillering status and planting needs of Oasis No. 1 in the second year.

[0062] In addition, the test farmland 1 area, under the same conditions, respectively, at the same time, corn monoculture (comparative example 1), oasis No. 1 monoculture (comparative example 2), oasis No. 1-fresh corn intercropping but without spraying any growth regulator (comparative example 3 and comparative example 4) comparative test. Corn monoculture, plant inter-row spacing is 50 cm, plant spacing is 30-40 cm. Oasis No. 1 monoculture, plant inter-row spacing is 1.0 m, plant spacing is 70 cm. In oasis No. 1-fresh corn intercropping, the planting mode of planting one row of oasis No. 1 and one row of corn is adopted. Among them, in comparative example 3, the row spacing of oasis No. 1 is 1.0 m, and the plant spacing is 80 cm. In comparative example 4, the row spacing of oasis No. 1 is 1.3 m, and the plant spacing is 60 cm. In the intercropping, corn is planted between two rows of oasis No. 1 and the distance is equal, and the corn plant spacing is 30-40 cm. The crop yield of different planting methods of monoculture and intercropping is measured, and the cadmium content in the straw and grain of oasis No. 1 and corn at harvest is measured. The extraction amount of cadmium in soil by plants is calculated according to the measured yield and cadmium content in plants, and the specific results are shown in Table 3.

[0063] In Table 2, for the sake of writing convenience, 2-(3,4-dichlorophenoxy) triethylamine is abbreviated as DCPTA, polyacrylamide is abbreviated as PAM, organic zinc selenide polyacrylamide solution is abbreviated as MPA-ZnSe / PAM, amino acid water-soluble fertilizer is abbreviated as AWF, 15% uniconazole calcium ring acid powder solution is abbreviated as (UC+PHC), medium element water-soluble fertilizer is abbreviated as MWF, ethylenediamine disuccinic acid is abbreviated as EDDS, and potassium polyacrylate is abbreviated as PAA.

[0064] Table 2: Scheme design of examples 1 to 8

[0065] Examples 5-8

[0066] The test area is selected from a controlled farmland in the north of Henan Province. The soil pH value of the place is 7.72, and the total cadmium content is 9.5 mg / kg, which exceeds the national standard risk screening value, and belongs to a heavy cadmium contaminated farmland, which is marked as test farmland 2.

[0067] The method of the present application is used for the remediation and utilization of the farmland under control, after the land consolidation according to the reference example 1, the test farmland 2 is planted with oasis No. 1 root bud by trenching and cutting at a row distance of 1.4 meters, the planting depth is 10-20 cm, the planting density is about 800 plants per mu, and irrigation is performed in time after planting to preserve soil moisture. In the middle and late April, when the ground temperature rises to above 10 DEG C, two rows of fresh corn Zhengnu2000 are sown in the middle of every two rows of oasis No. 1, one seed per hole, the sowing depth is 3.0-5.0 cm, and the plant spacing is 30-40 cm. The management, harvesting and the like of oasis No. 1 and fresh corn during the whole growth period are all referred to the reference example 1. During the growth period, the growth regulators GR-1, GR-2 and GR-3 of various formulations and the dosages are shown in Table 2.

[0068] In the second year, the fresh grass of oasis No. 1 grown in the test farmland 2 is sampled and analyzed, the cadmium content is 1.18-1.62 mg / kg, which exceeds the limit of cadmium in the health standard for forage grass, so in order to ensure the quality and safety of forage grass, the growth regulators still need to be sprayed. Meanwhile, the test farmland 2 may also have the situation that the oasis No. 1 has too many tillers, which leads to the row distance of oasis No. 1 being too narrow and being not conducive to the planting of fresh corn, so in the second year, whether to continue the intercropping planting of fresh corn can be selected according to the tillering condition and planting requirement of oasis No. 1.

[0069] In addition, under the same conditions, a comparative test is simultaneously performed in the test farmland 2, which is corn monocropping (comparative example 5), oasis No. 1 monocropping (comparative example 6), and oasis No. 1-fresh corn intercropping without spraying any growth regulator (comparative example 7). The plant spacing of corn monocropping is 50 cm, and the plant spacing is 30-40 cm. The plant spacing of oasis No. 1 monocropping is 1.4 m, and the plant spacing is 60 cm. In the oasis No. 1-fresh corn intercropping, the row distance between the two rows of oasis No. 1 is 1.4 m, and the plant spacing is 60 cm, two rows of corn are planted between the two rows of oasis No. 1, and the row distance between the adjacent two rows of crops is equal, and the corn plant spacing is 30-40 cm. The different planting modes of monocropping and intercropping are measured for plant yield, and the cadmium content in the harvested oasis No. 1, fresh corn straw and kernels is measured; the cadmium extraction amount of plants from the soil is calculated according to the measured yield and the cadmium content in the plants, and the specific results are shown in Table 4.

[0070] Test results

[0071] Table 3 The yield, cadmium content and cadmium extraction amount of oasis No. 1 and fresh corn in the test farmland 1

[0072]

[0073]

[0074] *Data is expressed as mean ± standard deviation, " / " indicates that it is not counted and calculated

[0075] From the analysis of the results in Table 3, in the test farmland 1, the cadmium content of the fresh grass of Oasis No. 1 under the single cropping treatment (Comparative Example 2) exceeded the limit requirement for cadmium in the forage grass hygiene standard (GB 13078-2017, cadmium limit of 88% dry basis 1.0 mg / kg). Under the intercropping treatment (Comparative Examples 3 and 4), the cadmium content of the fresh grass of Oasis No. 1 was reduced by 23.58% to 42.11% compared with the single cropping treatment, but still exceeded the limit requirement for cadmium in the forage grass hygiene standard. After applying the growth regulator to regulate the treatment, the cadmium content of the fresh grass of Oasis No. 1 in Examples 1 to 4 was reduced by 52.15% to 71.78% compared with the intercropping treatment, which met the requirements of the forage grass hygiene standard.

[0076] Under the single cropping treatment, the cadmium content of the corn stalks was near the limit requirement for cadmium in the forage grass hygiene standard; but under the intercropping treatment, the cadmium content of the corn stalks was further increased, which exceeded the limit requirement for cadmium in the forage grass hygiene standard, and after spraying the growth regulator (Examples 1 to 4), the cadmium in the corn stalks was controlled within the limit requirement of the forage grass hygiene standard, and compared with Comparative Examples 3 and 4, the cadmium content in the corn stalks of Examples 1 to 4 was reduced by 22.73% to 40.61%. The cadmium content in the corn kernels under all single cropping and intercropping treatments did not exceed the limit requirement for corn in the national food safety standard (GB 2762-2017, cadmium limit 0.1 mg / kg).

[0077] In addition, the intercropping treatment and the spraying regulation treatment also had different degrees of influence on the yield of the fresh grass of Oasis No. 1. Compared with the single cropping treatment, the yield of the fresh grass of Oasis No. 1 under the intercropping treatment (Comparative Examples 3 and 4) increased slightly, with a change of about 8.95% to 29.46%, and under the spraying regulation treatment (Examples 1 to 4), the yield of the fresh grass of Oasis No. 1 further increased by 49.42% to 99.59%.

[0078] After the fresh corn was harvested, Oasis No. 1 entered the slow growth period, so the growth regulator GR3 was sprayed on Oasis No. 1 to promote growth and enhance its absorption of cadmium, thereby improving the remediation efficiency of the planting mode. From the analysis of the results in Table 3, compared with the single cropping of Oasis No. 1, the dry grass yield of Oasis No. 1 increased by 17.18% to 36.64% and the absorption concentration of cadmium increased by 33.56% to 102.4% under the treatment of spraying the growth regulator GR-3 (Examples 1 to 4).

[0079] The Oasis No. 1 has slow tillering in the early stage of planting, low yield and low benefit. The fresh corn and the Oasis No. 1 are intercropped, the low yield of the Oasis No. 1 in the early stage of planting and the low soil equivalent ratio are compensated, the non-grain planting of the farmland soil is avoided, the absorption amount of the planting mode to the heavy metal is also improved. The Oasis No. 1 has the absorption amount of 4.08 g / mu to the cadmium in the soil, the intercropping of the Oasis No. 1 and the fresh corn (comparative examples 3 and 4) has the absorption amount of 9.35 g / mu and 8.37 g / mu to the cadmium, which is increased by 1.29 and 1.05 times; after the spraying regulation, the extraction amount of the cadmium of the examples 1-4 is increased to 9.38-13.80 g / mu, which is increased by 1.30-2.38 times, which shows that the intercropping + regulation treatment has a high extraction rate to the cadmium in the soil, and can achieve the effect of production and repair.

[0080] Table 4: The yield, cadmium content and cadmium extraction amount of the Oasis No. 1 and the fresh corn in the test farmland 2

[0081]

[0082]

[0083] The data is represented as mean ± standard deviation, and " / " represents that the statistics and accounting are not performed

[0084] The cadmium content of the soil in the test farmland 2 is 15.8 times of the soil pollution risk screening value, but the yield of the Oasis No. 1 and the Zhengnu 2000 corn variety planted in the test farmland is not inhibited by the cadmium, and because the test farmland is rested for several years, the organic matter and the cation exchange capacity of the soil are high, the above-ground yield of the plants in the test farmland 2 is higher than that in the test farmland 1, which shows that the Oasis No. 1 and the Zhengnu 2000 fresh corn selected in the application are cadmium-tolerant varieties. Similarly, in the test farmland 2, compared with the Oasis No. 1 monocropping treatment (comparative example 6), the Oasis No. 1 fresh grass yield in the intercropping treatment (comparative example 7) is increased by 19.84% and 16.39%; and in the examples 5-8, after the growth regulator is applied, the Oasis No. 1 fresh grass yield is increased by 23.86%-54.72%.

[0085] In Table 4, the cadmium content in the fresh corn kernels under single cropping and intercropping treatment meets the national food safety standards for the limit requirements of corn (GB 2762-2017, cadmium limit 0.1 mg / kg); the cadmium content of fresh grass of Oasis No. 1 under single cropping is far beyond the limit value of forage grass hygiene standard (GB 13078-2017, cadmium limit 1.0 mg / kg in 88% dry basis). Compared with single cropping treatment, the cadmium content in the fresh grass of Oasis No. 1 under intercropping treatment (Comparative Example 7) is reduced by 36.31% and 43.29%, which still exceeds the limit of cadmium in forage grass; after intercropping + spraying growth regulator treatment (Examples 5 to 8), the cadmium content in the fresh grass of Oasis No. 1 is reduced to the safety range of forage grass hygiene index, with a reduction of 77.84% to 85.21%.

[0086] The cadmium content in the fresh corn kernels under intercropping treatment is higher than that under single cropping treatment, but there is no significant difference between the treatments. Compared with corn single cropping treatment (Comparative Example 5), the cadmium content in the fresh corn stalks under intercropping treatment has a certain degree of increase, with an increase of 15.85%. After spraying the regulator, the cadmium content in the fresh corn stalks is reduced by 20.77% to 50.35%, which exceeds the limit requirement of forage grass hygiene standard, but meets the limit standard of cadmium in organic fertilizer (NY / T 525-2021, 3.0 mg / kg), which can be crushed and fermented for use as organic fertilizer after harvesting.

[0087] After the fresh corn is harvested in July, the growth regulator GR-3 is sprayed to enhance the absorption of cadmium in the soil by Oasis No. 1 and promote the growth of Oasis No. 1. As can be seen from the results in Table 4, compared with Comparative Example 6, the dry grass yield of Oasis No. 1 in Examples 5 to 8 is increased by 19.46% to 41.29%, and the cadmium content in the aboveground part of the plant is increased by 35.49% to 72.87%.

[0088] In Test Field 2, the annual extraction of cadmium from the soil under single cropping treatment of Oasis No. 1 (Comparative Example 6) is 10.14 g / acre, while after intercropping planting of Oasis No. 1 and corn (Comparative Example 7), the extraction of cadmium reaches 27.30 g / acre, which is increased by 1.69 times. In Examples 5 to 8, by spraying growth regulator for regulation and management, the extraction of cadmium reaches 26.22 to 31.66 g / acre, which is increased by 1.59 to 2.12 times.

Claims

1. A method for safe use of agricultural land under the control of the North, characterized by, It comprises the following steps: 1) land consolidation: land consolidation to the state of planting before planting; 2) crop planting: Oasis No. 1 and fresh corn are planted in an intercropping manner; the planting time of Oasis No. 1 is the end of March to the eve of Qingming, and the planting time of fresh corn is the middle and late of April; 3) crop management: when Oasis No. 1 is 6 leaves and 1 heart, spray growth regulator GR-1; when corn is 6 leaves and 1 heart, spray growth regulator GR-2; 4) crop harvesting: each Oasis No. 1 is harvested when it grows to 1-1.2 meters high; after the mature period of fresh corn in July, the mature corn ears are harvested in time; after the fresh corn ear harvesting is completed, the corn straw harvesting and crushing are completed by mechanical harvesting; 5) management and harvesting of Oasis No. 1 hay: after the harvesting of fresh corn, when Oasis No. 1 grows to 6 leaves and 1 heart, spray growth regulator GR-3; when Oasis No. 1 grows to 1.0-1.5 meters high, spray growth regulator GR-3 again, pay attention to soil moisture in between, and harvest Oasis No. 1 hay in January of the second year.

2. The method for safe use of agricultural land according to claim 1, wherein It also comprises the following steps: after harvesting Oasis No. 1 hay, rake the land, crush the stubble, and shallowly turn the residual stems and leaves in the field into the soil as green manure; continue to intercrop fresh corn in the spring of the second year, regularly harvest Oasis No. 1, and repeat a new round of intercropping, which is repeated 1-3 times.

3. The method for safe use of agricultural land according to claim 1, wherein The Oasis No. 1 is planted by root bud cutting method or seedling planting, with a plant spacing of 50-90 cm, a row spacing of 0.9-1.5 m, and a planting depth of 10-20 cm; irrigation is carried out within 1-2 days after planting to maintain soil moisture.

4. The method for safe use of agricultural land according to claim 1, wherein The cadmium content of the controlled agricultural land is not more than 10 mg / kg; when the cadmium content of the controlled agricultural land is 2.0-5.4 mg / kg, an intercropping method of planting one row of Oasis No. 1 and one row of corn is adopted, and the row spacing between two rows of Oasis No. 1 is 0.9-1.3 m; when the cadmium content of the controlled agricultural land is 5.4-10 mg / kg, an intercropping method of planting one row of Oasis No. 1 and two rows of corn is adopted, and the row spacing between two rows of Oasis No. 1 is 1.4-1.5 m; the corn is planted by dibbling or machine planting, and the planting depth is 3.0-5.0 cm.

5. The method for safe use of agricultural land according to claim 2, wherein During the first year of intercropping, Oasis No. 1 is harvested twice, and the first harvesting time is two months after planting the forage grass; after the second year, Oasis No. 1 is harvested 3-4 times, and the first harvesting time is early May; after the first harvesting, it is harvested again every 20-25 days, and the stubble height is 2-8 cm.

6. The method for safe use of farmland according to claim 5, wherein After each harvesting of Oasis No. 1, 10-15 kg of nitrogen, phosphorus and potassium compound fertilizer is applied per mu of land, and irrigation is carried out in time to maintain soil moisture.

7. The method for safe use of agricultural land according to claim 1, wherein In step 3), the growth regulator GR-1 is composed of 2-(3, 4-dichlorophenoxy) triethylamine, organic zinc selenide polyacrylamide solution and amino acid aqueous fertilizer with a mass ratio of (1.5-8.0) :(85-180) :(20-70); when spraying, the dosage is 100-400 g per mu of land, and the dilution ratio is 50-200 times.

8. The method for safe use of agricultural land according to claim 1, wherein In step 3), the growth regulator GR-2 is composed of 2-(3, 4-dichlorophenoxy) triethylamine, 15% of the triazole ring acid calcium powder liquid and the medium element water-soluble fertilizer with a mass ratio of (3.0~14) : (9~16) : (60~220); when spraying, the use amount is 50~400 g per mu, and the dilution ratio is 50~300 times.

9. The method for safe use of agricultural land according to claim 1, wherein In step 5), the growth regulator GR-3 is composed of 2-(3, 4-dichlorophenoxy) triethylamine, ethylenediamine disuccinic acid and polyacrylate potassium with a mass ratio of (1.0~6.0) : (8~14) : (20~50); when using, the use amount is 200~900 g per mu.

10. The method for safe utilization of farmland in northern regions as described in claim 7, characterized in that, The organic zinc selenide polyacrylamide solution is prepared by the following steps: a) Preparation of organic zinc selenide colloidal solution: 130~170 g of sodium oleate is dissolved in 20%~30% ethanol aqueous solution, then 10~15 g of zinc sulfate is added under inert gas atmosphere, and freshly prepared NaHSe solution is added during stirring and continues to stir for a certain time, so that the molar ratio of zinc to selenium is 3~5:1; the mixed solution is subjected to microwave reaction at 150~200℃ and 300~400 W for 30~60 min; after the reaction is completed, the solid powder is obtained by centrifugation, and the organic zinc selenide colloidal solution is obtained by ultrasonic dispersion with a volume ratio of 1:8~12 of mercaptopropionic acid-chloroform mixture and centrifugal separation; b) Preparation of polyacrylamide solution: 10~60 g of ethyl acetate, 60 g of 9%~12% acrylamide monomer aqueous solution, 6 g of 3% ethylenediaminetetraacetic acid disodium aqueous solution and 2 g of 0.4%~2% ammonium persulfate solution are mixed, and gradually heated to reflux, then 230 g of 9%~12% acrylamide monomer aqueous solution and 18 g of 0.4%~2% ammonium persulfate solution are added dropwise, respectively, and the dropping is completed within 1~3 h, and the reaction is continued for 2 h after the dropping is completed, and the mixture of ethyl acetate and water is evaporated under normal pressure, and the polyacrylamide solution with a solid content of 8%~12% and a molecular weight of 400~100 million is obtained after cooling; c) The organic zinc selenide colloidal solution, polyacrylamide solution and water prepared above are mixed in a mass ratio of (0.8~1.2) : (15~25) : (75~100), and oscillated for 6~8 h to obtain the product.

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