CN111955297A - Method for passivating heavy metals in rice field and increasing nitrogen retention amount - Google Patents

Abstract

The invention relates to a method for passivating heavy metals in paddy fields and increasing nitrogen fixation. The rice planting area is selected, and after applying basal fertilizer, rotary tillage and irrigation are performed to keep the water depth of 3-4 cm; ‑4cm; after the seedlings turn green, spray the microalgae bio-fertilizer water, regularly observe the surrounding organisms in the planting area, add the microalgae bio-fertilizer water according to the growth situation, and maintain the field surface water depth of 1‑2cm; after the rice harvesting is completed , retain the lower straw, and turn the surrounding organisms and straws in the paddy field into the ground by rotary tillage. The invention constructs the surrounding clump biological community by applying microalgae biological fertilizer, changes the soil pH through the photosynthesis and growth and metabolic activities of the algae, and secretes a large amount of extracellular polymers, so as to improve the heavy metal adsorption, passivation ability and biological function of the pericluster organisms. Nitrogen fixation ability. The method has the characteristics of low cost, flexibility and easy operation, and is a green ecological technology method.

Description

A method for passivating heavy metals in paddy fields and increasing nitrogen retention

technical field

The invention belongs to the fields of agriculture and environmental protection, relates to the fields of heavy metal passivation and fertility improvement in paddy fields, and in particular relates to a method for passivating heavy metals and increasing nitrogen retention in paddy soil.

Background technique

Heavy metal pollution is one of the main types of soil pollution. In my country and even in the world, due to the discharge of industrial and mining wastes and the excessive use of pesticides, heavy metals accumulate in the soil around industrial and mining areas and in farmland, and the quality of soil health deteriorates. Therefore, soil heavy metal pollution remediation technology has attracted much attention. Cadmium (Cd) is a heavy metal element with strong biological toxicity. It has strong chemical activity in the environment and long-lasting toxicity. It is easy to endanger human health through enrichment in the food chain and induce liver, kidney and bone lesions. Remediation methods for heavy metal contaminated soil such as cadmium include physical remediation, chemical remediation and bioremediation. Physical restoration mainly includes foreign soil, soil leaching and electric restoration. Although the restoration effect is good, the cost is high. Chemical remediation mainly reduces the bioavailability of heavy metals by adding chemical reagents (such as lime, phosphate rock powder, etc.), but long-term application can easily cause soil compaction and damage soil structure. Bioremediation includes phytoextraction and microbial remediation. Phytoextract is enriched by hyperaccumulating plants, and then heavy metals are removed by collecting plants. However, this method takes up a lot of land and affects food production. Microbial remediation is to reduce the bioavailability of heavy metals in soil and reduce the risk of heavy metals entering crops by using some microorganisms with functions such as adsorption and precipitation of heavy metals. In addition, the cadmium-contaminated soil has low nutrients, which can passivate heavy metals while improving the bioavailability of soil nutrients, which is helpful to achieve the simultaneous and stable improvement of crop quality and yield.

Numerous studies have shown that microbial remediation can effectively reduce the bioavailability of heavy metals and reduce crop absorption. CN110922977A discloses a method for applying a microbial soil remediation agent to the remediation of heavy metal polluted soil, mainly using compound bacterial preparations (Bacillus licheniformis, Pseudomonas, Bacillus subtilis, Clostridium butyricum, etc.), surfactants, mature organic matter , humic acid, clay, fly ash, carboxymethyl chitosan, etc., improve the physical and chemical properties of soil through surfactants, and finally improve the enrichment ability of microbial agents, decomposed organic matter, humic acid, etc. to heavy metals. However, in this method, the components of the remediation agent are complex, and the water content of the soil needs to be maintained at 25-40% to ensure the remediation effect. CN106591277A discloses a preparation and application method of Bacillus with functions of passivating heavy metals and dephosphorizing, mainly by expanding the cultivation of Bacillus cereus, then adding biochar to its fermentation broth and continuing to cultivate to obtain immobilized Bacillus, Thus, while reducing the bioavailability of cadmium, the content of available phosphorus in the soil is increased to ensure the growth of crops. However, the bacteria used in the invention is a single bacterial species (Bacillus cereus), which is passivated when the niche changes in the field environment. The effect of heavy metals and phosphorus removal will be greatly reduced.

Rice is one of the main food crops in my country, and the rice planting area in China reaches 30 million hectares. However, monitoring shows that the seasonal utilization rate of nitrogen fertilizer in rice planting in my country is less than 30%, and the high loss rate is the main reason for the low nitrogen utilization rate. Among the lost nitrogen, nitrogen lost in liquid forms such as runoff About 10% of the fertilization amount. Increasing nitrogen retention in paddy fields is of great significance for improving nitrogen use efficiency and reducing nitrogen loss.

In conclusion, how to improve the nitrogen retention capacity and reduce nitrogen loss in paddy fields while reducing the bioavailability of heavy metals is an urgent problem to be solved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the deficiencies of the prior art, and to provide a method for passivating heavy metals in paddy fields and increasing nitrogen retention.

Technical solutions

Surrounding organisms are microbial aggregates formed in flooded environments, mainly composed of algae, bacteria and their extracellular polymers intertwined, with abundant populations and strong adaptability to the environment. The inventor's research found that there are many adsorption sites on the algal cell wall in the periwinkle organisms, which can adsorb a large amount of heavy metals, and the extracellular polymers secreted by the periwinkle organisms can also adsorb and complex heavy metals, and strengthen the passivation of heavy metals. In addition, the inventors also found that pericluster organisms can efficiently absorb nitrogen, and their nitrogen content is up to 10% (dry weight). Releases nitrogen into the soil in the short term, increasing soil nitrogen content and bioavailability. Based on this, the present invention aims to reduce the bioavailability of heavy metals in paddy soil and increase soil nitrogen fixation, and adopts the working idea of "first in situ culturing pericytes in paddy fields, and then constructing a heavy metal passivation and nitrogen fixation system", The design is based on the route of "biological culture and community optimization of peripheral clumps - passivation of heavy metals - increase of nitrogen fixation" to provide a method for passivating heavy metals in paddy fields and increasing nitrogen fixation. The specific scheme is as follows:

A method for passivating heavy metals in paddy fields and increasing nitrogen retention, comprising the steps of:

(1) choose the rice planting area, after applying the base fertilizer, utilize the rotary tiller to carry out the rotary tilling to the rice planting area, then irrigate, and keep the water depth to be 3-4cm;

(2) transplant the rice seedlings to the rice planting area, and keep the water depth of the field surface to be 3-4cm;

(3) after the rice seedlings turn green, evenly spray the microalgae bio-fertilizer water in the field surface water, and the microalgae bio-fertilizer water is formed by mixing the microalgae bio-fertilizer and water with a mass ratio of 1:(8-12), so the The microalgae biofertilizer is a mixture of freeze-dried No. algae, Spirogyra and biochar; the growth of the surrounding organisms in the rice planting area is regularly observed, and the microalgae biofertilizer water is added according to the growth situation, and the surface water of the paddy field is maintained. The depth is 1-2cm;

(4) After the rice is harvested, keep the lower straws, use a rotary tiller for rotary tillage, turn the surrounding organisms and straws in the paddy field into the ground, the rotary tillage depth is 8-10cm, and plant rice or other crops after rotary tillage .

Further, in step (1), the amount of base fertilizer applied per mu of rice planting area is: nitrogen fertilizer 150-180kg N/ha, phosphate fertilizer 50-60kg P/ha, potassium fertilizer 60-75kg K/ha.

Further, in step (1), the rotary tillage depth is 8-12cm.

Further, in step (3), the consumption of microalgae biological fertilizer water is 20-25kg/mu.

Further, in step (3), in the microalgae biological fertilizer, the dry weight ratio of Nostia, Spirogyra and biochar is 1:1:3.

Beneficial effects of the present invention: The present invention provides a method for passivating heavy metals in paddy fields and increasing nitrogen retention. The method constructs a pericluster biological community by applying microalgae biological fertilizer, so that cyanobacteria and green algae grow rapidly to form pericluster organisms The community, through the photosynthesis and growth metabolism of algae, changes the soil pH, and secretes a large amount of extracellular polymers, which improves the heavy metal adsorption and passivation ability of the surrounding organisms, and the biological nitrogen fixation and inorganic nitrogen absorption capacity. In the passivation of heavy metals such as cadmium , At the same time of increasing soil nitrogen, the surrounding biological residues can also increase soil organic matter content, improve soil environmental quality and improve soil fertility from various aspects, and have good ecological and environmental benefits and economic benefits. The method of the invention has the characteristics of low cost, flexibility and easy operation, and is a brand-new and green ecological technology method.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

The experiment was carried out in a rice field in Gejiu City, Yunnan Province

A method for passivating heavy metals in paddy fields and increasing nitrogen retention, comprising the steps of:

(1) Select 1 mu of paddy field and apply base fertilizer, the specific dosage is: nitrogen fertilizer 150kg N/ha, phosphate fertilizer 60kg P/ha, potassium fertilizer 70kg K/ha. Use a rotary tiller to perform rotary tillage in the rice planting area, the rotary tillage depth is 10cm, and then irrigate to keep the water depth at 3cm;

(2) transplanting rice seedlings to the rice planting area, and keeping the water depth of the field surface to be 3cm;

(3) after the rice seedlings turn green, evenly spray the microalgae bio-fertilizer water in the field surface water, the microalgae bio-fertilizer water consumption is 20kg/mu, and the microalgae bio-fertilizer water is composed of the microalgae bio-fertilizer and water at a ratio of 1:10 The microalgae bio-fertilizer is a mixture of freeze-dried Candida, Spirogyra and biochar (the dry weight ratio of Candida, Spirogyra and biochar is 1:1:3); The preparation method of the fertilizer: adding biochar to the culture solution of Candida and Spirogyra, centrifuging to remove the supernatant, and then adding 2% trehalose as a protective agent for freeze-drying;

Observing the growth of pericluster organisms in the rice planting area every week, adding microalgae bio-fertilizer water according to the growth situation to ensure the secretion of extracellular polymers, nitrogen absorption and biological nitrogen fixation of perineum organisms, and maintain the surface water depth of the paddy field. is 2cm.

(4) After the rice is harvested, keep the lower straws, measure the soil total nitrogen content, available Cd content and Cd content in the rice, use a rotary tiller to perform rotary tillage, and turn the surrounding organisms and straws in the paddy field into the ground, The depth of rotary tillage is 8-10cm, and rice or other crops are planted after rotary tillage.

Taking the non-sprayed microalgae biological fertilizer as the comparative example 1, the rest are the same as the examples.

The results of the determination of the nitrogen content of the surrounding organisms and soil, and the Cd content of different forms of soil and rice showed that the coverage rate of the surrounding organisms in the paddy field in Example 1 was 26%, which was significantly higher than that of Comparative Example 1, which was 15%. The number of microbial OTUs in the paddy field soil of Example 1 also increased by 12% compared with that of Comparative Example 1; the total nitrogen content of the topsoil of paddy field in Comparative Example 1 was 1.2-1.4 g/kg, while that of Example 1 reached 1.5-1.7 g/kg; The soil-available Cd content of Example 1 was 1.1-1.2 mg/kg, and that of Example 1 was 0.9-1.0 mg/kg; the Cd content of rice in Comparative Example 1 was 4.0-4.2 mg/kg, while that of Example 1 was 2.1-3.4 mg/kg.

Example 2

The experiment was carried out in a rice field in Gejiu City, Yunnan Province

A method for passivating heavy metals in paddy fields and increasing nitrogen retention, comprising the steps of:

(1) Select 1 mu of paddy field and apply base fertilizer, the specific dosage is: nitrogen fertilizer 180kg N/ha, phosphate fertilizer 50kg P/ha, potassium fertilizer 65kg K/ha. Use a rotary tiller to perform rotary tillage in the rice planting area, the rotary tillage depth is 10cm, and then irrigate to keep the water depth at 4cm;

(2) transplanting rice seedlings to the rice planting area, and keeping the water depth of the field surface to be 4cm;

(3) after the rice seedlings turn green, evenly spray the microalgae bio-fertilizer water in the field surface water, the microalgae bio-fertilizer water consumption is 25kg/mu, and the microalgae bio-fertilizer water is composed of the microalgae bio-fertilizer and water at a ratio of 1:10 The microalgae bio-fertilizer is a mixture of freeze-dried Candida, Spirogyra and biochar (the dry weight ratio of Candida, Spirogyra and biochar is 1:1:3);

Observing the growth of pericluster organisms in the rice planting area every week, adding microalgae bio-fertilizer water according to the growth situation to ensure the secretion of extracellular polymers, nitrogen absorption and biological nitrogen fixation of perineum organisms, and maintain the surface water depth of the paddy field. is 2cm. The preparation method of the microalgae biological fertilizer: adding biochar to the culture solution of Nostoc and Spirogyra, centrifuging to remove the supernatant, and then adding 2% trehalose as a protective agent for freeze-drying;

(4) After the rice is harvested, keep the lower straws, measure the soil total nitrogen content, available Cd content and Cd content in the rice, use a rotary tiller to perform rotary tillage, and turn the surrounding organisms and straws in the paddy field into the ground, The depth of rotary tillage is 10cm, and rice or other crops are planted after rotary tillage.

Taking the non-sprayed microalgae biological fertilizer as the comparative example 2, the rest are the same as the embodiment.

The results of the determination of the nitrogen content of the surrounding organisms and soil, and the content of Cd in different forms of soil and rice show that the coverage rate of the surrounding organisms in the paddy field in Example 2 is 22%, which is significantly higher than that of Comparative Example 2, 15%. The number of microbial OTUs in the paddy field soil of Example 2 also increased by 11% compared with that of Comparative Example 2; the total nitrogen content of the topsoil of paddy field in Comparative Example 2 was 1.2-1.4 g/kg, while that of Example 2 reached 1.6-1.7 g/kg; The soil-available Cd content of Example 2 was 1.1-1.2 mg/kg, and that of Example 2 was 0.8-0.9 mg/kg; the Cd content of rice in Comparative Example 2 was 4.0-4.2 mg/kg, while that of Example 2 was 2.1-3.1 mg/kg.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (5)

1. a method for passivating heavy metals in paddy field and increasing nitrogen holding capacity, is characterized in that, comprises the steps: (1) choose the rice planting area, after applying the base fertilizer, utilize the rotary tiller to carry out the rotary tilling to the rice planting area, then irrigate, and keep the water depth to be 3-4cm; (2) transplant the rice seedlings to the rice planting area, and keep the water depth of the field surface to be 3-4cm; (3) after the rice seedlings turn green, evenly spray the microalgae bio-fertilizer water in the field surface water, and the microalgae bio-fertilizer water is formed by mixing the microalgae bio-fertilizer and water with a mass ratio of 1:(8-12), so the The microalgae biofertilizer is a mixture of freeze-dried No. algae, Spirogyra and biochar; the growth of the surrounding organisms in the rice planting area is regularly observed, and the microalgae biofertilizer water is added according to the growth situation, and the surface water of the paddy field is maintained. The depth is 1-2cm; (4) After the rice is harvested, keep the lower straws, use a rotary tiller for rotary tillage, turn the surrounding organisms and straws in the paddy field into the ground, the rotary tillage depth is 8-10cm, and plant rice or other crops after rotary tillage . 2. the method for passivating heavy metals in paddy field as claimed in claim 1 and increasing nitrogen holding capacity, it is characterized in that, in step (1), the basal fertilizer application rate of every mu of rice planting area is: nitrogen fertilizer 150-180kg N/ha, phosphate fertilizer 50-60kg P/ha, potash 60-75kg K/ha. 3. The method for passivating heavy metals in paddy fields and increasing nitrogen retention as claimed in claim 1, wherein in step (1), the depth of rotary tillage is 8-12cm. 4. the method for passivating heavy metals in paddy field as claimed in claim 1 and increasing nitrogen holding capacity, is characterized in that, in step (3), the consumption of microalgae biological fertilizer water is 20-25kg/mu. 5. the method for passivating heavy metals in paddy field as claimed in claim 1 or 2 or 3 or 4 and increasing nitrogen holding capacity, it is characterized in that, in step (3), in described microalgae biological fertilizer, Nostia, Spirogyra and Spirogyra spp. The dry weight ratio of biochar was 1:1:3.