Activating agent capable of being used for improving nitrogen fixation activity of farmland soil in situ and preparation method of activating agent

Abstract

The invention discloses an activating agent capable of being used for improving the nitrogen fixation activity of farmland soil in situ and a preparation method of the activating agent, and relates to the technical field of agricultural chemistry. The activating agent is prepared from the biochar, the sodium molybdate, the goethite and the rutile as raw materials and is used for improving the nitrogen fixation activity of the farmland soil in situ. On the premise of not adding exogenous strains, by activating existing indigenous nitrogen-fixing microbial communities in farmland soil and stimulating high-efficiency expression of related nitrogen-fixing functional genes in a soil environment, in-situ activation of the nitrogen-fixing potential of the soil is achieved, and the nitrogen-fixing performance of the soil is improved. The activator for in-situ improvement of the nitrogen fixation activity of the farmland soil has a synergistic effect on improving the content of ammonium nitrogen in the soil and the activity of nitrogenase, has the outstanding advantages of high in-situ adaptability, precise action targeting, sustained and lasting nutrition release, environment friendliness, low cost and the like, can remarkably reduce the use of chemical fertilizers, and has a good application prospect. And sustainable development of green agriculture is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agrochemical technology, in particular to an activator for in-situ improvement of soil nitrogen fixation activity in farmland and a preparation method thereof. BACKGROUND

[0002] Soil, as the basic resource for agricultural production, its quality directly affects the growth and development of crops. With the continuous growth of population, the demand for agricultural products has increased significantly. Under the background of long-term intensive farming and excessive use of chemical fertilizers and pesticides, the problem of soil quality degradation is becoming increasingly serious. Among them, nitrogen deficiency in soil is one of the key factors limiting agricultural production, and nitrogen affects crop yield and quality. Traditionally, the lack of soil nitrogen is compensated by applying chemical nitrogen fertilizer, but long-term excessive use not only leads to soil compaction, acidification and decline of organic matter, but also causes a series of environmental problems such as water eutrophication and greenhouse gas emissions.

[0003] In order to solve this problem, soil nitrogen fixation improvement technology has emerged, mainly including microbial fertilizer, soil conditioner, etc. Among them, microbial fertilizer is a kind of specific beneficial bacteria, which can improve soil properties and increase crop yield when applied to soil through microbial action. However, most of the microbial fertilizers will have the problem of not being suitable for the soil, resulting in unstable effect; soil conditioner is a kind of material used to improve soil physical, chemical or biological properties, which can repair soil structure, adjust pH, reduce pollution and optimize soil quality when applied to soil through physical adsorption, chemical regulation or promotion of microbial activity. However, the above-mentioned soil nitrogen fixation improvement technologies generally have the technical bottlenecks of weak colonization ability of strains, unstable field effect, insignificant nitrogen fixation effect and short shelf life of products. In addition, in the process of biological nitrogen fixation, 16 ATP and 8 electrons are needed to fix one part of nitrogen, and specific nitrogenase catalysis is needed to achieve it. Therefore, it is urgent to seek a technology that improves the inherent soil fertility from the perspective of providing energy, elements needed for nitrogenase synthesis and beneficial living habitat for biological nitrogen fixation process, activates indigenous nitrogen-fixing microbial community and awakens related nitrogen fixation gene function, so as to realize in-situ activation of soil nitrogen fixation potential and improvement of system nitrogen fixation performance.

[0004] In the prior art, CN108640791A discloses a biochar soil remediation agent, which comprises biochar loaded with titanium dioxide, trace elements (sodium molybdate), biological bacteria liquid, compound fertilizer and compost material. The soil remediation agent can not only adsorb and degrade pollutants in the soil, but also can increase the content of organic matter and microorganisms in the soil. In the patent, the photocatalytic oxidation of TiO2 is used to degrade the organic pollutants adsorbed by biochar into water and CO2 under light conditions. However, the patent does not mention that the biochar loaded with titanium dioxide can improve the nitrogen fixation activity of the soil, and the patent still needs to rely on the addition of bacterial liquid to provide nitrogen-fixing microorganisms. CN116574518A discloses an organic improver, which comprises goethite modified biochar, microbial inoculum, corn straw and wheat straw biochar. The goethite modified biochar can make the microbial inoculum colonize, and at the same time, form an organic-mineral interface of microaggregates in the soil, which can well activate the soil and the activity of the added microorganisms, and inhibit the process of decomposition of organic matter by microorganisms, thereby maintaining the soil fertility. However, the patent mainly uses the addition of modified biochar and exogenous microbial inoculum to achieve the effect of improving soil fertility, and does not mention that goethite can provide energy for the nitrogen fixation process of indigenous nitrogen-fixing microorganisms in the soil, thereby improving the nitrogen fixation performance of the soil.

[0005] Therefore, there is a need to develop a soil activator for activating nitrogen-fixing microbial communities and awakening related nitrogen fixation functional genes, so as to realize in-situ activation of soil nitrogen fixation potential and improvement of soil nitrogen fixation performance. SUMMARY

[0006] In view of the above prior art, the purpose of the present application is to provide a soil activator for in-situ improvement of soil nitrogen fixation activity in farmland and a preparation method thereof. The activator is prepared by using biochar, sodium molybdate, goethite and red goldstone as raw materials, and is used for in-situ improvement of soil nitrogen fixation activity in farmland. Without adding exogenous bacterial strains, the indigenous nitrogen-fixing microbial communities in the farmland soil are activated, the related nitrogen fixation functional genes are awakened, and the efficient expression in the soil environment is promoted, so as to realize in-situ activation of soil nitrogen fixation potential and improvement of soil nitrogen fixation performance. The activator for in-situ improvement of soil nitrogen fixation activity in farmland developed by the present application has the advantages of strong in-situ adaptability, precise targeting, long-lasting nutrient release, environmental friendliness and low cost, and can significantly reduce the use of chemical fertilizers, thereby realizing sustainable development of green agriculture. In addition, the biochar, sodium molybdate, goethite and red goldstone have a synergistic effect on increasing the content of ammonium nitrogen in the soil and the activity of nitrogen fixation enzyme.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In a first aspect of the present application, a soil activator for in-situ improvement of soil nitrogen fixation activity in farmland is provided. The activator is prepared by using sodium molybdate, goethite and red goldstone in a ratio of (0.15-0.45):(2.5-7.5):(2.5-7.5).

[0008] Preferably, the mass ratio of sodium molybdate, goethite and red goldstone is 0.3:5:5.

[0009] Preferably, the ammonium molybdate is sodium molybdate dihydrate with a molybdenum content of 38%-39%.

[0010] In a second aspect of the present application, the above-mentioned activator is used in (1)-(2) as follows: (1) increasing the nitrogen fixation enzyme activity in soil; (2) increasing the content of ammonium nitrogen in soil.

[0011] In a third aspect of the present application, a method for increasing the nitrogen fixation activity of soil is provided, comprising the following steps: The above-mentioned activator for in-situ increasing the nitrogen fixation activity of farmland soil is mixed with corn straw biochar to obtain a mixture; the mixture is added to the soil, the soil is placed under anaerobic and light conditions after adjusting the water content of the soil, and the soil is cultured.

[0012] Preferably, the corn straw biochar is prepared by the following method: The corn straw is calcined at 450-550℃ for 1.5-2.5h under the condition of oxygen isolation, and then washed and dried to obtain the corn straw biochar.

[0013] Further, the specific treatment of the washing operation is that the calcined solid is sequentially washed in ultrapure water and ethanol solution for 3 times. Preferably, the concentration of the ethanol solution is 93%-98%.

[0014] Further, the drying temperature is 50-70℃, and the drying time is 4-6h.

[0015] Preferably, the mass ratio of the activator for in-situ increasing the nitrogen fixation activity of farmland soil and corn straw is (5-15.5):(1000-2000).

[0016] Preferably, the mass ratio of the mixture and the soil is 1:(80-120).

[0017] Preferably, the water content of the soil is adjusted to 23%-27%.

[0018] Preferably, the culture temperature is 23-27℃, the culture humidity is 65%-70%, and the culture time is 28-32d.

[0019] The beneficial effects of the present application are: 1.The application adopts biochar, sodium molybdate, goethite and red goldstone as raw materials to prepare an activator for in-situ improving the nitrogen fixation activity of farmland soil.Under the premise of not adding exogenous strains, the existing indigenous nitrogen fixation microbial community in farmland soil is activated and the related nitrogen fixation functional genes are awakened, so as to realize in-situ activation of soil nitrogen fixation potential and improvement of soil nitrogen fixation performance.The activator prepared by the application for in-situ improving the nitrogen fixation activity of farmland soil has the advantages of strong in-situ adaptability, precise targeting, long-lasting nutrient release, environmental friendliness and low cost, etc., which can significantly reduce the use of chemical fertilizers and promote the sustainable development of green agriculture.

[0020] In addition, biochar, sodium molybdate, goethite and red goldstone have a synergistic effect on improving the content of ammonium nitrogen in soil and the activity of nitrogen fixation enzyme.

[0021] 2.In the activator prepared by the application for in-situ improving the nitrogen fixation activity of farmland soil, the biochar has the characteristics of slow release, rich functional groups and pore structure, can adsorb and continuously supply nutrients, and ensure the steady growth of microorganisms; the goethite and red goldstone can generate photoelectrons under light conditions to strengthen the original reducing power of the soil, thereby improving the nitrogen fixation activity of the soil; the sodium molybdate and goethite can provide the molybdenum element and iron element necessary for the core FeMo-co factor of the nitrogen fixation enzyme in the soil, and target to improve the gene expression of the nitrogen fixation microorganism nifH and the activity of the nitrogen fixation enzyme.It can be seen that in the application, biochar is used to build an excellent survival environment for nitrogen fixation microorganisms, goethite and red goldstone provide energy for the biological nitrogen fixation process, and goethite and sodium molybdate provide the required elements for the nitrogen fixation enzyme, thereby activating the indigenous nitrogen fixation microbial community and awakening the related nitrogen fixation functional genes, so as to realize in-situ activation of the nitrogen fixation potential of the soil and improvement of the nitrogen fixation performance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 : Figure of the percentage of ammonium nitrogen content improvement in the soil of different treatment groups in test example 1; Figure 2 : Figure of the percentage of nitrogen fixation enzyme activity improvement in the soil of different treatment groups in test example 1. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0024] In order to enable those skilled in the art to have a clearer understanding of the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0025] The experimental materials used in the embodiments of the present application are all conventional experimental materials in the art and can be purchased through commercial channels.

[0026] The red gold stone is purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., and the goethite is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The molybdenum content of ammonium molybdate dihydrate refers to the mass fraction of molybdenum in ammonium molybdate dihydrate.

[0027] Example 1: Method for improving soil nitrogen fixation activity (1) The corn straw is crushed to 1.5 cm, and under the condition of oxygen isolation, it is calcined at 500℃ for 2h, and then the calcined solid is washed with ultrapure water and 95% ethanol solution respectively for 3 times, and then the washed solid is dried at 60℃ for 5h to obtain corn straw biochar particles; (2) The ammonium molybdate dihydrate with a molybdenum content of 38%-39%, the red gold stone and the goethite are mixed uniformly according to a mass ratio of 0.3:5:5 to obtain an activator for in-situ improving soil nitrogen fixation activity of farmland; (3) The corn straw biochar particles and the activator for in-situ improving soil nitrogen fixation activity of farmland are mixed according to a mass ratio of 1500:10.3 to obtain a mixture; The mixture is added to the soil, the mass ratio of soil and mixture is controlled to be 100:1, the soil water content is adjusted to 25%, and then the mixture is cultured in an incubator under anaerobic and light conditions at 25℃ and humidity of 66% for 30d to achieve the effect of improving soil nitrogen fixation activity.

[0028] Example 2: Method for improving soil nitrogen fixation activity (1) The corn straw is crushed to 1cm, and under the condition of oxygen isolation, it is calcined at 450℃ for 1.5h, and then the calcined solid is washed with ultrapure water and 95% ethanol solution respectively for 3 times, and then the washed solid is dried at 50℃ for 4h to obtain corn straw biochar particles; (2) The ammonium molybdate dihydrate with a molybdenum content of 38%-39%, the red gold stone and the goethite are mixed uniformly according to a mass ratio of 0.15:2.5:2.5 to obtain an activator for in-situ improving soil nitrogen fixation activity of farmland; (3) The corn straw biochar particles and the activator for in-situ improving soil nitrogen fixation activity of farmland are mixed uniformly according to a mass ratio of 1000:5.15 to obtain a mixture; The mixture is added to the soil, the mass ratio of soil and mixture is controlled to be 80:1, the soil water content is adjusted to 23%, and then the mixture is cultured in an incubator under anaerobic and light conditions at 23℃ and humidity of 65% for 28d to achieve the effect of improving soil nitrogen fixation activity.

[0029] Example 3: Method for improving soil nitrogen fixation activity (1) Corn straw was crushed to 2 cm, and then was calcined at 550℃ for 2.5 h under the condition of oxygen isolation. The calcined solid was washed with ultrapure water and 95% ethanol solution by mass fraction in sequence for 3 times, and then was dried at 70℃ for 6 h to obtain corn straw biochar particles; (2) Ammonium molybdate dihydrate containing 38%-39% of molybdenum, red gold stone and goethite were mixed uniformly according to a mass ratio of 0.45:7.5:7.5 to obtain an activator for in-situ improving soil nitrogen fixation activity in farmland; (3) The corn straw biochar particles and the activator for in-situ improving soil nitrogen fixation activity in farmland were mixed uniformly according to a mass ratio of 2000:15.45 to obtain a mixture; The mixture was added to the soil, and the mass ratio of the soil and the mixture was controlled to be 120:1. After adjusting the water content of the soil to 27%, the mixture was cultured in an incubator at 27℃ and 70% humidity under anaerobic and light conditions for 32 d to achieve the effect of improving soil nitrogen fixation activity.

[0030] Test Example 1: Microcosm test This test example sets up 5 treatment groups, which are as follows: Treatment group 1: corn straw biochar is used as a soil treatment agent; Treatment group 2: corn straw and sodium molybdate are mixed according to a mass ratio of 1500:10.3 as a soil treatment agent; Treatment group 3: corn straw and red gold stone are mixed according to a mass ratio of 1500:10.3 as a soil treatment agent; Treatment group 4: corn straw and goethite are mixed according to a mass ratio of 1500:10.3 as a soil treatment agent; Treatment group 5: corn straw and the activator prepared in Example 1 are mixed according to a mass ratio of 1500:10.3 as a soil treatment agent; The specific test steps are as follows: 160 g of fresh soil was weighed and placed in a 250 mL culture bottle. After adding and mixing the corresponding soil treatment agent of each treatment group, the mass ratio of the soil treatment agent and the soil was 1:100, and the water content of the soil was adjusted to 25%. The culture bottle was sealed with a rubber plug, and the gas in the culture bottle was replaced with N2 / CO2(v / v: 80% / 20%). Each treatment was set in triplicate, and the culture bottles were placed in an incubator at 25℃ and 66% humidity for light culture for one month to simulate the natural field environment.

[0031] After the culture, the soil samples of each treatment group were taken, acetylene reduction method was used to determine the soil nitrogen fixation enzyme activity, and gas chromatography (Shimadzu GC2014) was used to determine the soil nitrogen fixation enzyme activity; ultraviolet spectrophotometry was used to determine the content of ammonium nitrogen in the soil, so as to evaluate the nitrogen fixation effect of each treatment on the soil, and the results are shown in Table 1 and Figure 1

[0032] Table 1 Soil ammonium nitrogen content and nitrogen fixation enzyme activity of different treatment groups As shown in Table 1, after the application of the activator prepared by compounding sodium molybdate, red goldstone and goethite, the ammonium nitrogen content in the soil is 2.57 mg / kg, and the nitrogen fixation enzyme activity is 59.23 nmol / (g·soil·h), compared with treatment group 1, the ammonium nitrogen content is increased by 0.82 mg / kg, and the nitrogen fixation enzyme activity is increased by 9.99 nmol / (g·soil·h). Compared with treatment group 1, the ammonium nitrogen content in the soil is increased by 0.12 mg / kg, 0.04 mg / kg and 0.08 mg / kg respectively when sodium molybdate, red goldstone and goethite are used as activators alone, and the nitrogen fixation enzyme activity is increased by 2.38 nmol / (g·soil·h), 1.51 nmol / (g·soil·h) and 1.7 nmol / (g·soil·h) respectively. It can be seen that the sodium molybdate, red goldstone and goethite used as activators in the present application have a synergistic effect in improving the ammonium nitrogen content and the nitrogen fixation enzyme activity.

[0033] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. An activator which can be used to enhance the nitrogen fixation activity of the soil in situ in a farmland, characterized in that, The activator is composed of sodium molybdate, goethite, and rutile in a ratio of (0.15-0.45):(2.5-7.5):(2.5-7.5).

2. The application of the activator of claim 1, which can be used to improve nitrogen fixation activity in farmland soil in situ, in the following (1)-(2): (1) Increase the activity of nitrogenase in the soil; (2) Increase the content of ammonium nitrogen in the soil.

3. A method of increasing nitrogen fixation activity in soil, characterized by, Includes the following steps: The activator described in claim 1, which can be used to improve nitrogen fixation activity in farmland soil in situ, is mixed with corn straw biochar to obtain a mixture. The mixture is added to the soil, the soil moisture content is adjusted, and then it is cultured under anaerobic and light conditions.

4. The method for improving soil nitrogen fixation activity as described in claim 3, characterized in that, Corn stalk biochar is prepared by the following method: Corn stalks were calcined at 450-550℃ for 1.5-2.5 hours under oxygen-free conditions, and then washed and dried to obtain corn stalk biochar.

5. The method for improving soil nitrogen fixation activity as described in claim 4, characterized in that, The calcined solid was washed three times in ultrapure water and ethanol solution; the drying temperature was 50-70℃ and the drying time was 4-6h.

6. The method for improving soil nitrogen fixation activity as described in claim 3, characterized in that, The mass ratio of the activator and corn stalks that can be used to improve nitrogen fixation activity in farmland soil in situ is (5-15.5):(1000-2000).

7. The method for improving soil nitrogen fixation activity as described in claim 3, characterized in that, The mass ratio of the mixture to the soil is 1:(80-120).

8. The method for improving soil nitrogen fixation activity as described in claim 3, characterized in that, Adjust the soil moisture content to 23%-27%.

9. The method for improving soil nitrogen fixation activity as described in claim 3, characterized in that, The culture temperature is 23-27℃, the culture humidity is 65%-70%, and the culture time is 28-32 days.

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