Method for improving soil fertility and enzyme activity of rice field by using nitrogen-fixing cyanobacteria biological membrane

Abstract

The invention relates to a method for improving soil fertility and enzyme activity of a rice field by using a nitrogen-fixing cyanobacteria biological membrane, which comprises the following steps: step 1, expanding propagation of nitrogen-fixing cyanobacteria: selecting anabaena globifera as a rice field application algae species, and performing expanding culture on the algae species to obtain a nitrogen-fixing cyanobacteria secondary algae species; step 2, applying nitrogen-fixing cyanobacteria: applying the nitrogen-fixing cyanobacteria in a rice base fertilizer period and a tillering period, and replacing part of chemical fertilizer with the nitrogen-fixing cyanobacteria to reduce the application amount of the chemical fertilizer; secondly, the nitrogen-fixing cyanobacteria returns to the rice field through biological nitrogen fixation and rotting decomposition of dead algae, the content of nitrogen and carbon in the soil is increased, the soil fertility is improved, and the nitrogen-fixing cyanobacteria can provide nutrient substances for microorganisms in the soil, improve the enzyme activity of the soil and improve the quality of the soil when applied to the rice field.

Description

Technical Field

[0001] The invention relates to the field of algae biotechnology and soil fertilization technology, and in particular to a method for improving paddy field soil fertility and enzyme activity by utilizing nitrogen-fixing cyanobacteria biofilm. Background Art

[0002] As an important food crop, rice is the staple food of more than half of the Chinese population, and its planting area accounts for about 1 / 4 of the world's total rice planting area. my country's agricultural production development faces severe challenges such as increasing food demand, less per capita arable land, and limited high-quality arable land resources. In recent years, in order to ensure high crop yields, excessive fertilizers have been applied to rice fields for a long time, resulting in soil structure damage, decreased soil fertility, reduced soil enzyme activity, and low comprehensive fertilizer utilization rate.

[0003] Improving soil fertility and enzyme activity and improving soil quality are important measures to maintain soil nutrient transformation and efficient absorption and utilization, and are also key ways to maintain long-term stable crop yields. At present, the application of organic fertilizers and returning straw to the field can effectively improve paddy field soil fertility and soil enzyme activity. However, organic fertilizers have a short shelf life, poor survival effect, complex raw materials, and are prone to secondary pollution after fertilizer application; in addition, the higher price of organic fertilizers compared to chemical fertilizers is also an important factor restricting its development. Although returning straw to the field has been proven to significantly improve soil fertility and enzyme activity under certain conditions, the effect of returning straw to the field in some areas is not good, and even crop yields have decreased after returning to the field. Due to the long degradation cycle of straw in the soil, it is not completely decomposed during the crop growth cycle, which is not conducive to root growth. Long-term large amounts of crop residues are not completely decomposed, providing a medium for pathogens or pests, and creating a suitable humidity and temperature environment for their growth, thereby exacerbating the occurrence of pests and diseases, seriously endangering soil health and interfering with crop growth. Algae have great potential as a fertilizer source in improving the quality of paddy soil and are low in cost. However, the application of nitrogen-fixing cyanobacteria fertilizers in paddy fields is greatly affected by the weather environment, and their stable survival during the specific growth period of rice still faces great challenges. Summary of the invention

[0004] In order to solve the problem of reduced soil fertility and enzyme activity in paddy fields due to long-term excessive application of chemical fertilizers, the present invention provides a method for improving paddy field soil fertility and enzyme activity by utilizing nitrogen-fixing cyanobacteria biofilm, which is used to improve soil structure and soil quality.

[0005] To achieve the above object, the present invention adopts the following technical scheme, a method for improving paddy soil fertility and enzyme activity by using nitrogen-fixing cyanobacteria biofilm, comprising the following steps:

[0006] Step 1. Propagating nitrogen-fixing cyanobacteria, selecting Anabaena sphaerocephala as an algae species, and expanding and culturing the algae species to obtain a secondary algae species of nitrogen-fixing cyanobacteria;

[0007] Step 2. Apply nitrogen-fixing cyanobacteria during the basal fertilizer period and tillering period of rice.

[0008] Preferably, the Anabaena sphaerocephala in step 1 is Anabaena sphaerocephala (FACHB-251) obtained from the Freshwater Algae Seed Bank of the Chinese Academy of Sciences.

[0009] Preferably, the method for culturing algae species to obtain nitrogen-fixing cyanobacteria in step 1 comprises:

[0010] Step 101. Inoculate the algae into a 500 mL conical flask filled with BG-110 liquid culture medium and place the algae in a flask under a light intensity of 6×10 3 Lx, a light / dark cycle of 12h / 12h, and a culture temperature of 30±1°C were used to culture the algae until the logarithmic growth phase to obtain the primary algae species. During the culture process, the flask was shaken 4 times a day to disperse the nitrogen-fixing cyanobacteria, increase the contact between the nitrogen-fixing cyanobacteria and the culture medium, and reduce the aggregation of the nitrogen-fixing cyanobacteria.

[0011] Step 102. Transfer the primary algae to a 5 L narrow-mouth glass bottle filled with BG-110 liquid culture medium and place it under a light intensity of 6 × 10 3 Lx, a light / dark cycle of 12h / 12h, a culture temperature of 30±1℃, and an aeration rate of 3-6L / h, the nitrogen-fixing cyanobacteria were cultured to the logarithmic growth phase. During the aeration culture, a microporous filter with a 0.22μm cellulose acetate membrane should be installed at the ventilation pipe port.

[0012] Preferably, after the cultivation of nitrogen-fixing cyanobacteria is completed, it needs to be collected according to the following method:

[0013] The cultured nitrogen-fixing cyanobacteria and culture solution were placed under a light intensity of 9600 Lx, and when the nitrogen-fixing cyanobacteria aggregated into algae films, they were collected using a 2 mm pore nylon mesh.

[0014] Preferably, the nitrogen-fixing cyanobacteria and the culture solution are kept stationary for 4 hours under a light intensity of 9600 Lx.

[0015] Preferably, in step 2, the ratio of nitrogen-fixing cyanobacteria applied during the basal fertilizer period and the tillering period is 3:2.

[0016] The beneficial effects of the present invention are:

[0017] Nitrogen-fixing cyanobacteria are a type of prokaryotic microorganisms that can perform photosynthesis. They reproduce quickly, have strong adaptability, and have the ability to fix nitrogen biologically. They can reduce free nitrogen in the air to ammonia and are an important source of nitrogen in the soil. The long-term flooding of the surface of rice fields and the high temperature and humidity provide a good environment for the rapid growth of nitrogen-fixing cyanobacteria, which greatly reduces the management cost of nitrogen-fixing cyanobacteria as fertilizer. First, using nitrogen-fixing cyanobacteria to replace part of chemical fertilizers can reduce the amount of chemical fertilizers applied; second, nitrogen-fixing cyanobacteria return to rice fields through biological nitrogen fixation and the decay and decomposition of dead algae, which increases the nitrogen and carbon content in the soil and improves soil fertility. Finally, applying nitrogen-fixing cyanobacteria to rice fields can provide nutrients for microorganisms in the soil, increase soil enzyme activity, and improve soil quality. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the embodiments.

[0019] The nitrogen-fixing cyanobacteria used in this embodiment can not only fix free nitrogen through biological nitrogen fixation, but also lyse and release its own nitrogen when algal cells die to provide the required nitrogen for plants, promote plant growth and increase yield, and is a very promising alternative fertilizer source. At the same time, nitrogen-fixing cyanobacteria can also improve soil structure, fix free CO2 through photosynthesis, and thus increase the organic matter content in the soil. Compared with chemical nitrogen fertilizers, nitrogen-fixing cyanobacteria as a fertilizer source can increase soil microbial activity and soil enzyme activity. Nitrogen-fixing cyanobacteria can secrete growth-promoting substances, and using them as a biological fertilizer source can improve the environmental adaptability of crops. The application of nitrogen-fixing cyanobacteria to rice fields in the form of biofilms greatly reduces the loss of nitrogen-fixing cyanobacteria and improves the stability of nitrogen-fixing cyanobacteria as a fertilizer source.

[0020] Example 1: Method for improving soil fertility and enzyme activity in paddy fields by using nitrogen-fixing cyanobacteria under potted conditions

[0021] In order to practice the inventive method, the present invention is further described below in conjunction with a specific implementation method. The steps are:

[0022] The nitrogen-fixing cyanobacteria species selected in this embodiment are from Anabaena globosum (FACHB-251) in the freshwater algae species bank of the Chinese Academy of Sciences. The obtained Anabaena globosum is expanded and cultured to obtain nitrogen-fixing cyanobacteria;

[0023] (1) inoculating the original seed into a 500 mL conical flask filled with BG-110 liquid culture medium, and aerating and culturing until the logarithmic growth phase to obtain a primary algae seed;

[0024] (2) The primary algae strain was transferred into a 5 L narrow-mouth glass bottle filled with BG-110 liquid culture medium and cultured with aeration until the logarithmic growth phase to obtain a sufficient amount of nitrogen-fixing cyanobacteria required for the experiment;

[0025] During the cultivation of nitrogen-fixing cyanobacteria, the light intensity was 6×103 Lx, light / dark cycle was 12 h / 12 ​​h, culture temperature was 30 ± 1 °C, and ventilation was 3-6 L / h;

[0026] (3) When collecting nitrogen-fixing cyanobacteria, the dispersed algae liquid was transferred into a flat-bottomed basin (length, width, and height: 50×40×15 cm, respectively) and placed under strong light (9600 Lx). When the nitrogen-fixing cyanobacteria aggregated into an algae film, they were collected using a 2 mm pore nylon mesh. One-fifth of the algae liquid was retained each time as the next batch of algae for expansion. Before applying nitrogen-fixing cyanobacteria, it must be placed in a light incubator with a light intensity of 9600 Lx for 4 hours, so that the nitrogen-fixing cyanobacteria can use photosynthesis to produce gas and float to the surface of the culture medium to form an algae film, ensuring that the nitrogen-fixing cyanobacteria grow well in the surface layer of water overlying the rice.

[0027] (4) The test soil was collected from a rice-growing area in Xinyang City, dried naturally, crushed, and passed through a 10-mesh sieve for later use. The rice variety used for the test was Liangyou 6326.

[0028] (5) Application of nitrogen-fixing cyanobacteria: Under potted conditions, nitrogen-fixing cyanobacteria are propagated in advance according to the growth period of rice, and fresh algae are applied during the basal fertilizer period and tillering period. During the application process, the nitrogen-fixing cyanobacteria are first collected and processed, and the moisture content of the fresh algae is measured, and the nitrogen content of the dry algae is measured, and then the application is based on this;

[0029] (6) Experimental design: Four treatment groups were set up. The CK treatment group was a blank treatment group, without any fertilizer; the CN treatment group was a conventional fertilization treatment group; the ZF30 treatment group was a nitrogen-fixing cyanobacteria replacing 30% of conventional chemical fertilizers; the ZF50 treatment group was a nitrogen-fixing cyanobacteria replacing 50% of chemical fertilizers. Each treatment group was set up with 3 replicates. 4.5 kg of naturally air-dried soil was weighed into each pot and placed in a flowerpot (22 cm in diameter and 24 cm in height). Water was added to maintain a water depth of 5 cm, and 3 rice seedlings were transplanted into each pot. The conventional fertilization treatment group applied nitrogen (N), phosphorus (P2O5), and potassium (K2O) at 10kg, 5kg, and 10kg per mu, respectively. The ZF30 treatment group and the ZF50 treatment group applied 3kg and 5kg (calculated by dry weight) fresh algae per mu to replace 30% and 50% of chemical fertilizers, respectively, and applied twice at a ratio of 60% and 40% of the total application amount during the basal fertilizer period and tillering period. Phosphate fertilizer (calcium magnesium phosphate, 12% P2O5) and potash fertilizer (potassium chloride, 60% K2O) were applied once at 41.7kg / mu and 16.7kg / mu during the basal fertilizer period in the conventional fertilization treatment group, respectively. Phosphate fertilizer and potash fertilizer of other treatment groups were applied once at the rice basal fertilizer period according to the experimental design ratio.

[0030] The application of nitrogen-fixing cyanobacteria biofilm in rice fields can, on the one hand, attach itself to the stems and leaves of rice and grow stably in the water surface above the rice fields, thus improving the ability to withstand adverse weather. On the other hand, the nitrogen fixed by nitrogen-fixing cyanobacteria returns to the rice field soil after cell death and decomposition, increasing the content of nutrients such as carbon and nitrogen in the rice field soil, improving soil structure and increasing soil enzyme activity.

[0031] Replacing chemical nitrogen fertilizers with nitrogen-fixing cyanobacteria biofilms can reduce the use of chemical fertilizers by 30%-50% within a certain range (Table 1).

[0032] Table 1 Application amount of urea and nitrogen-fixing cyanobacteria in different treatment groups

[0033]

[0034] As can be seen from Table 2, after the rice pot experiment, the physical and chemical properties of the soil were improved to a certain extent. Compared with the conventional fertilization treatment group (CN), the soil alkaline nitrogen content of the nitrogen-fixing cyanobacteria biofilm replacing 30% of the chemical fertilizer treatment group (ZF30) still increased by 5.19%, the effective phosphorus content increased by 5.27%, and the soil organic matter content increased by 6.11%. When the nitrogen-fixing cyanobacteria biofilm replaced 50% of the chemical fertilizer, the soil alkaline nitrogen content still increased by 13.98%, the effective phosphorus content increased by 7.27%, and the soil organic matter content increased by 13.33%.

[0035] Table 2 Changes in soil physicochemical properties under nitrogen-fixing cyanobacteria biofilm conditions

[0036] CK CN ZF30 ZF50 Alkaline nitrogen (mg / kg) 42.66 54.67 59.51 62.31 Available phosphorus (mg / kg) 87.61 89.35 93.99 95.85 Organic matter (g / kg) 14.15 18.88 20.03 21.39

[0037] When nitrogen-fixing cyanobacteria biofilm replaced 30% of chemical fertilizers, soil acid phosphatase activity increased by 39.18%, soil urease activity increased by 19.18%, and protease activity increased by 5.62%. When nitrogen-fixing cyanobacteria biofilm replaced 50% of chemical fertilizers, soil acid phosphatase activity increased by 62.39%, soil urease activity increased by 23.63%, and protease activity increased by 11.41%.

[0038]

[0039] The above embodiments are merely examples of the present invention and do not limit the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for improving paddy soil fertility and enzyme activity using nitrogen-fixing cyanobacteria biofilm, characterized in that: The following steps are involved: Step 1. Propagating nitrogen-fixing cyanobacteria, selecting Anabaena sphaerocephala as an algae species, and expanding and culturing the algae species to obtain a secondary algae species of nitrogen-fixing cyanobacteria; Step 2. Apply nitrogen-fixing cyanobacteria during the basal fertilizer period and tillering period of rice.

2. The method of improving paddy soil fertility and enzyme activity by using nitrogen-fixing cyanobacteria biofilm according to claim 1, characterized in that: The Anabaena globosporum in step 1 is Anabaena globosporum (FACHB-251) obtained from the Freshwater Algae Seed Bank of the Chinese Academy of Sciences.

3. The method of improving paddy soil fertility and enzyme activity by using nitrogen-fixing cyanobacteria biofilm according to claim 1, characterized in that: The method for culturing the algae species in step 1 to obtain nitrogen-fixing cyanobacteria comprises: Step 101. Inoculate the algae into a 500 mL conical flask filled with BG-110 liquid culture medium and place the algae in a flask under a light intensity of 6×10 3 Lx, a light / dark cycle of 12h / 12h, and a culture temperature of 30±1°C were used to culture the algae until the logarithmic growth phase to obtain the primary algae species. During the culture process, the flask was shaken 4 times a day to disperse the nitrogen-fixing cyanobacteria, increase the contact between the nitrogen-fixing cyanobacteria and the culture medium, and reduce the aggregation of the nitrogen-fixing cyanobacteria. Step 102. Transfer the primary algae to a 5 L narrow-mouth glass bottle filled with BG-110 liquid culture medium and place it under a light intensity of 6 × 10 3 Lx, a light / dark cycle of 12h / 12h, a culture temperature of 30±1℃, and an aeration rate of 3-6L / h, the nitrogen-fixing cyanobacteria were cultured to the logarithmic growth phase. During the aeration culture, a microporous filter with a 0.22μm cellulose acetate membrane should be installed at the ventilation pipe port.

4. The method of improving paddy soil fertility and enzyme activity by using nitrogen-fixing cyanobacteria biofilm according to claim 3, characterized in that: After the cultivation of nitrogen-fixing cyanobacteria is completed, it needs to be collected as follows: The cultured nitrogen-fixing cyanobacteria and culture solution were placed under a light intensity of 9600 Lx, and when the nitrogen-fixing cyanobacteria aggregated into algae films, they were collected using a 2 mm pore nylon mesh.

5. The method for improving paddy soil fertility and enzyme activity by using nitrogen-fixing cyanobacteria biofilm according to claim 4, characterized in that: The static time of nitrogen-fixing cyanobacteria and culture solution under light intensity of 9600Lx is 4h.

6. According to the method for improving paddy soil fertility and enzyme activity by utilizing nitrogen-fixing cyanobacteria biofilm as claimed in claim 1, the ratio of applying nitrogen-fixing cyanobacteria in the basal fertilizer stage and the tillering stage in step 2 is 3:2.

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