Method for improving soil fertility and crop growth

Abstract

The invention discloses a method for improving soil fertility and crop growth, and belongs to the technical field of soil science and plant nutrition. According to the method, pig manure biochar is prepared after pig manure is pyrolyzed, the prepared pig manure biochar is added into soil, then escherichia coli bacterial suspension is applied to the soil once a week and is continuously applied for 6-8 weeks, and after treatment through the method, compared with untreated soil, the soil is converted from acidity to neutrality, and the soil has the advantages that the content of the escherichia coli bacterial suspension in the soil is increased; the contents of N, P and K elements in the soil are increased, and the maximum increase rate of total nitrogen is 78.7%; the maximum increase rate of total phosphorus is 218.4%; the maximum increase rate of total potassium is 12.8%; the maximum improvement rate of the soluble organic carbon is 273.6%; the activity of the sucrase in the soil is also remarkably improved, and the maximum improvement rate is 82.1%; crops are planted in the soil subjected to combined treatment of the pig manure biochar and the escherichia coli, so that the growth of the crops can be effectively improved, and the growth is mainly represented by the increase of the plant height and the increase of the fresh weight of the crops.

Description

Technical Field

[0001] The present invention relates to a method for improving soil fertility and crop growth, belonging to the technical fields of soil science and plant nutrition. Background Art

[0002] During the planting process of crops, in order to improve the quality of crops, people often apply various chemical fertilizers. The use of chemical fertilizers increases the planting costs of farmers. According to statistics, the excessive use of chemical fertilizers causes the planting costs of farmers to increase by 15% - 30%, but the increased production income is less than 5%. Moreover, the excessive use of chemical fertilizers will cause the following harms:

[0003] Firstly, it will cause the degradation of the soil system, specifically manifested as: the deterioration of soil physical and chemical properties and the inhibition of microbial activity.

[0004] The long-term excessive application of chemical fertilizers will lead to soil acidification, hardening, destruction of the aggregate structure, reduction of air permeability and water retention capacity, accelerated loss of elements such as calcium and magnesium, decrease of base saturation, and significant reduction of fertility; the number of soil microorganisms in the areas with excessive application of chemical fertilizers decreases by 40% - 60%.

[0005] Secondly, it will lead to the accumulation of harmful substances in vegetables. Research shows that excessive nitrogen fertilizer makes the nitrate in vegetables exceed the standard by 2 - 3 times, and the carcinogenic risk of converting nitrate into nitrosamine in the human body increases.

[0006] The excessive use of chemical fertilizers will also exacerbate environmental pollution. Research shows that the loss of chemical fertilizers will cause the nitrogen and phosphorus in the water bodies around more than 30% of the farmlands to exceed the standard, triggering the explosive reproduction of algae; and the raw materials for producing phosphate fertilizers contain heavy metals such as cadmium and arsenic. Long-term use will increase the heavy metal content in the soil by 20% - 50%, and will threaten human health through the food chain.

[0007] Finally, the excessive use of chemical fertilizers will affect human health. Direct contact with chemical fertilizer dust can cause respiratory inflammation and skin irritation. Summary of the Invention

[0008] In order to solve the problems existing in the use of fertilizers in the current crop planting, the present invention provides a method for improving soil fertility and crop growth. The specific method is: applying pig manure biochar and Escherichia coli bacterial suspension in the soil for planting crops. Among them, the Escherichia coli bacterial suspension is applied once a week for 6 - 8 consecutive weeks, and the pig manure biochar only needs to be applied once at the beginning, and there is no need to add it again later.

[0009] Preferably, the addition amount of pig manure biochar per kilogram of soil is 15 - 25 g, and 10 mL of Escherichia coli bacterial suspension is applied corresponding to each gram of pig manure biochar.

[0010] Preferably, the preparation method of the Escherichia coli bacterial suspension is as follows: First, obtain an Escherichia coli bacterial solution, centrifuge the bacterial solution to retain the bacteria, and resuspend the bacteria with sterile normal saline to obtain an Escherichia coli bacterial suspension. The OD 600 of the Escherichia coli bacterial suspension is 0.6 - 1.0.

[0011] Preferably, the Escherichia coli is non - pathogenic Escherichia coli.

[0012] Preferably, the non - pathogenic Escherichia coli is Escherichia coli K12 MG1665.

[0013] Preferably, the preparation method of the pig manure biochar is as follows: Naturally air - dry the pig manure, crush it, and then pyrolyze it to obtain pig manure biochar.

[0014] Preferably, the pyrolysis conditions are as follows: The nitrogen gas flow rate is 0.5 - 0.6 L / min, the heating rate is 8 - 12 °C / min, the heat - preservation temperature is 300 °C - 700 °C, and the heat - preservation time is 1.5 - 2.5 h.

[0015] The technical effects of the present invention:

[0016] (1) Pig manure biochar has both high nutrition and high specific surface area, and is more suitable for cooperation with functional bacteria. Traditional microbial agents are mainly nitrogen - fixing bacteria and phosphorus - solubilizing bacteria, with high costs and poor adaptability; while the Escherichia coli K12 MG1665 strain has low costs and clear metabolic pathways, and has better compatibility with pig manure biochar.

[0017] (2) Compared with existing chemical fertilizers, the combined use of the pig manure biochar and Escherichia coli of the present invention has higher safety, will not cause secondary pollution to the environment, and will not cause harm to the human body.

[0018] (3) The combined use of pig manure biochar and Escherichia coli in the present invention can significantly improve soil fertility in 6 - 8 weeks, meeting the growth cycle requirements of crops.

[0019] (4) The present invention uses pig manure as the raw material to prepare biochar, solves the environmental problems brought by traditional pig manure treatment, realizes the resource utilization of agricultural waste, promotes the development of agricultural circular economy, and conforms to the principles of green chemistry. Specific embodiments

[0020] The following further describes the present invention in detail with specific embodiments, but the protection scope of the present invention is not limited to the content described.

[0021] Example 1

[0022] Preparation of pig manure biochar

[0023] The collected pig manure was air-dried and then crushed into powder in a pulverizer. The treated pig manure was placed in a crucible and pyrolyzed in a muffle furnace. The nitrogen flow rate was 0.5 L / min, and the heating rate was 10 °C / min. It was kept warm at 300 °C, 500 °C, or 700 °C for 2 h. After pyrolysis, it was taken out after the temperature dropped below 70 °C. After cooling to room temperature, the pig manure biochar was crushed and passed through a 100-mesh sieve and then stored in the dark. In this example, the pig manure biochar obtained by pyrolysis at 300 °C was numbered PB300; the pig manure biochar obtained by pyrolysis at 500 °C was numbered PB500; the pig manure biochar obtained by pyrolysis at 700 °C was numbered PB700.

[0024] Kitchen waste biochar KB and corn straw biochar MB were prepared under the conditions of 300 °C, 500 °C, and 700 °C by the same method, and their numbers were KB300, KB500, KB700, MB300, MB500, and MB700 respectively.

[0025] Example 2

[0026] Preparation of Escherichia coli suspension

[0027] For Escherichia coli, the non-pathogenic K12 MG1665 strain, which is commonly used as a model organism, was selected. The specific preparation steps are as follows:

[0028] (1) Activation of Escherichia coli: Escherichia coli was activated with LB liquid medium. A small amount of bacterial liquid was aspirated and inoculated into LB liquid medium and cultured at 37 °C and 150 rpm until the logarithmic growth phase OD 600 was 0.7 to obtain the activated bacterial suspension.

[0029] (2) Preparation of Escherichia coli suspension: The activated bacterial suspension was inoculated into LB liquid medium at a volume ratio of 1:100 and cultured at 37 °C and 150 rpm until OD 600 was 0.9. The bacterial cells were collected by centrifugation at 4 °C and washed with sterile normal saline with a mass concentration of 0.85%. The mixture was adjusted to OD 600 to 0.9 to obtain the Escherichia coli suspension

[0030] Example 3

[0031] Combined use of pig manure biochar and Escherichia coli to improve the growth of pakchoi

[0032] The biochar and Escherichia coli suspension used in this example were prepared from Example 1 and Example 2.

[0033] A total of 14 groups of experiments were conducted in this embodiment. In the first group, neither pig manure biochar nor Escherichia coli suspension was used; in the second group, only Escherichia coli suspension was used; in the third group, only pig manure biochar PB300 was used; in the fourth group, pig manure biochar PB300 and Escherichia coli suspension were used; in the fifth group, only pig manure biochar PB500 was used; in the sixth group, pig manure biochar PB500 and Escherichia coli suspension were used; in the seventh group, only pig manure biochar PB700 was used; in the eighth group, pig manure biochar PB700 and Escherichia coli suspension were used; in the ninth group, kitchen waste biochar KB300 and Escherichia coli suspension were used; in the tenth group, kitchen waste biochar KB500 and Escherichia coli suspension were used; in the eleventh group, kitchen waste biochar KB700 and Escherichia coli suspension were used; in the twelfth group, corn straw biochar MB300 and Escherichia coli suspension were used; in the thirteenth group, corn straw biochar MB500 and Escherichia coli suspension were used; in the fourteenth group, corn straw biochar MB700 and Escherichia coli suspension were used.

[0034] The usage methods of biochar and Escherichia coli suspension are as follows:

[0035] When biochar and Escherichia coli suspension are used together: 20 g of biochar is added to each kilogram of soil, and 10 mL of Escherichia coli suspension is applied corresponding to each gram of biochar. The Escherichia coli suspension is applied once a week, and the weekly application amount is 200 mL / m 2 , and the plant height and fresh weight of pakchoi are measured after 6 weeks.

[0036] When only pig manure biochar is used, 20 g of biochar is added to each kilogram of soil, and the plant height and fresh weight of pakchoi are measured after 6 weeks.

[0037] When only Escherichia coli suspension is used, the Escherichia coli suspension is applied once a week, and the weekly application amount is 200 mL / m 2 , and the plant height, fresh weight of pakchoi and the indexes of soil fertility are measured after 6 weeks.

[0038] During the experiment, in order to detect that the combined use of Escherichia coli liquid and pig manure biochar can improve the soil fertility, groups with the same treatment but without planting pakchoi were set up. After detection, the soil fertility in different treatment groups is shown in Table 1.

[0039] Table 1 Soil fertility of different treatment groups

[0040]

[0041]

[0042] As can be seen from Table 1, the effect of solely applying Escherichia coli on soil pH improvement is not obvious. After jointly applying pig manure biochar and Escherichia coli, the improvement effect is obvious, turning the acidic soil into neutral, which is beneficial to plant growth. The sole application of Escherichia coli has little improvement on total nitrogen, total phosphorus, total potassium, and dissolved organic carbon in the soil. The addition of pig manure biochar in combination with Escherichia coli can further increase the contents of total nitrogen, total phosphorus, total potassium, and dissolved organic carbon in the soil. Compared with the blank control group, the maximum increase rate of total nitrogen is 78.7%; the maximum increase rate of total phosphorus is 218.4%; the maximum increase rate of total potassium is 12.8%; the maximum increase rate of dissolved organic carbon is 273.6%; the maximum increase rate of soil sucrase activity is 82.1%. N, P, K, and C elements are important criteria for measuring soil fertility, and different biochars at each temperature have different improvement effects on the four elements, which can be flexibly selected according to actual situations. The sole application of Escherichia coli slightly reduces the soil sucrase activity, while the combined application of pig manure biochar and Escherichia coli significantly increases it. Soil sucrase plays a key role in the enzymatic degradation of soil organic carbon, and the difference in enzyme activity is related to the composition of soil organic matter. Therefore, soil enzyme activity can be used as a sensitive indicator of changes in soil conditions and health status. Compared with food waste biochar and corn straw biochar, pig manure biochar shows better effects in improving various soil fertility indicators.

[0043] The plant heights and fresh weights of pakchoi in different groups were measured as shown in Table 2.

[0044] Table 2 Plant Heights and Fresh Weights of Pakchoi in Different Treatment Groups

[0045]

[0046] As can be seen from Table 2, the sole application of Escherichia coli and pig manure biochar has little improvement on the plant height and fresh weight, especially Escherichia coli. The combined use of pig manure biochar and Escherichia coli solution at three temperatures significantly improves the plant height and fresh weight, especially in terms of the fresh weight of plants. Compared with food waste biochar, pig manure biochar plays a significant positive role. Compared with corn straw biochar, the effect of pig manure biochar is also more significant. Pig manure biochar and Escherichia coli solution form an efficient symbiotic system, strengthening nutrient transformation and plant growth stimulation. These characteristics make it significantly superior to corn straw with single nutrients and weak microbial interaction and food waste biochar with unstable nutrients and poor synergy in promoting the plant height of stem and leaf development and the fresh weight of biomass accumulation, and it is especially suitable for plant species with large fertilizer requirements and sensitive to biological stimulation.

[0047] In summary, the sole application of Escherichia coli basically has no improvement on various soil fertility indicators. The sole application of pig manure biochar has an obvious but limited improvement effect. However, after the combined application of pig manure biochar and Escherichia coli, a better improvement effect can be achieved, reaching the effect of "1 + 1 > 2".

Claims

1. A method for improving soil fertility and crop growth, characterized in that: Apply swine manure biochar and Escherichia coli suspension to the soil where crops are planted. The Escherichia coli suspension is applied once a week for 6 - 8 consecutive weeks, and the swine manure biochar is applied only once at the beginning.

2. The method for improving soil fertility and crop growth according to claim 1, characterized in that: The addition amount of swine manure biochar in each kilogram of soil is 15 - 25 g, and 10 mL of Escherichia coli suspension is applied corresponding to each gram of swine manure biochar.

3. The method for improving soil fertility and crop growth according to claim 1, characterized in that: The preparation method of the Escherichia coli bacterial suspension is as follows: First, obtain an Escherichia coli bacterial solution, centrifuge the bacterial solution to retain the bacterial cells, and resuspend the bacterial cells with sterile physiological saline to obtain an Escherichia coli bacterial suspension. The OD 600 of the Escherichia coli bacterial suspension is 0.6 to 1.

0.

4. The method for improving soil fertility and crop growth according to claim 1, characterized in that: The Escherichia coli is non - pathogenic Escherichia coli.

5. The method for improving soil fertility and crop growth according to claim 4, characterized in that: The non - pathogenic Escherichia coli is Escherichia coli K12 MG1665.

6. The method for improving soil fertility and crop growth according to claim 1, characterized in that: The preparation method of the swine manure biochar is as follows: The swine manure is naturally air - dried, crushed, and then pyrolyzed to obtain swine manure biochar.

7. The method for improving soil fertility and crop growth according to claim 6, characterized in that: The pyrolysis conditions are: the nitrogen gas flow rate is 0.5 - 0.6 L / min, the heating rate is 8 - 12 °C / min, the heat - preservation temperature is 300 °C - 700 °C, and the heat - preservation time is 1.5 - 2.5 h.

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