A method of improving soil in a northern region interplanted with sunflower in a celery continuous cropping land

Abstract

The application relates to a northern region interplanting sunflower improved celery continuous cropping land soil method, which is characterized by comprising the following steps: (1) land preparation and fertilization; (2) film covering and drip irrigation belt (1) laying; (3) setting plant row spacing; (4) staggered planting; (5) field management during symbiosis; (6) celery harvesting; (7) sunflower field management; (8) sunflower harvesting; (9) straw returning to field; according to the soil characteristics and environmental conditions of the northern region celery continuous cropping land, the application proposes celery and sunflower interplanting cultivation, vertical distribution difference is formed in the soil by the shallow root system of the celery and the deep root system of the sunflower, the two crops are planted in a 'pin' shape, horizontal distribution difference is also formed by the plant row spacing, thereby effectively avoiding the competition of the two crops for soil nutrients during symbiosis, reducing soil secondary salinization, increasing soil organic matter, probiotics, and simultaneously increasing unit area output value.

Description

Technical Field

[0001] This invention relates to the field of celery cultivation technology, and in particular to a method for improving the soil in celery-planting fields in northern regions by intercropping sunflowers. Background Technology

[0002] Celery belongs to the Apiaceae family. Northern my country, with its large diurnal temperature range, cool climate, and abundant sunshine and heat resources, provides favorable conditions for the development of the celery industry. Open-field cultivation mainly involves planting from May to July in summer and harvesting from August to October in autumn. Due to its high economic returns, continuous cropping of celery has become a common planting method adopted by farmers. However, farmers often use excessive amounts of chemical fertilizers during production, and in some areas, even use slightly saline groundwater for irrigation. After two years of continuous cropping, secondary salinization occurs in the soil. Years of continuous cropping reduce the richness and diversity of rhizosphere soil microorganisms, alter the microbial structure, and cause an imbalance in the rhizosphere microbial environment. The number of beneficial bacteria gradually decreases, while the number of pathogens accumulates and increases. The problem of continuous cropping of celery is becoming increasingly serious, generally resulting in yield reductions of more than 10%, and in some cases up to 30%. This not only restricts normal vegetable production but also seriously reduces the quality of vegetables. In particular, secondary soil salinization leads to the accumulation of nitrates and nitrites in vegetable products, which are harmful to human health.

[0003] Currently, there are several methods for soil improvement: (1) Soil leaching, which generally requires flood irrigation. In northern my country, rainfall is low, which wastes a lot of freshwater resources. The salt from leaching can also cause non-point source pollution to the surrounding environment. (2) Crop rotation, which generally involves planting gramineous crops such as wheat and corn, and legume crops such as broad beans and peas in the second year. Although this method is green and pollution-free, the production cycle is long and the economic benefits are low, making it difficult to promote. (3) Chemical methods, which generally involve applying broad-spectrum fungicides such as metalaxyl, copper hydroxide, and pyraclostrobin. This method will kill both harmful and beneficial bacteria in the soil. Although the short-term effect is significant, long-term use also poses a certain risk of environmental pollution. Therefore, it is urgent to invent a method for improving the soil of celery-continuously cropped land. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, a method for improving soil conditions in celery-continuous cropping fields by intercropping sunflowers is proposed in northern regions, in order to solve the problems mentioned in the background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: (a) Land preparation and fertilization; (ii) Laying drip irrigation tape under mulch film: On the prepared ground, lay mulch film, and under each mulch film, lay drip irrigation tape evenly at equal intervals of 46cm; (III) Setting plant spacing: Determine the celery planting holes 11-12cm on both sides of the drip irrigation tape, with a celery row spacing of 22-24cm and a celery plant spacing of 22-24cm; Determine the sunflower planting holes in the center of four celery plants every two rows of celery, with a sunflower row spacing of 44-48cm and a sunflower plant spacing of 44-48cm. (iv) Staggered planting: Celery can be planted after the frost period in the north. Select celery seedlings with 5 to 6 true leaves for planting. Irrigate immediately after planting to make the relative moisture content of the soil at 1 to 40 cm reach 80% to 90% to facilitate seedling establishment. Celery is usually transplanted 30 to 40 days after transplanting. Sunflowers are then transplanted, selecting seedlings with 2 to 3 true leaves. Immediately after transplanting, water should be applied to ensure that the relative moisture content of the soil at a depth of 1 to 40 cm reaches 80% to 90%, which will help the seedlings recover. (v) Field management during the co-existence period: Irrigate 3 to 5 times during the co-existence period of celery and sunflower, always keeping the relative moisture content of the soil at 1 to 40 cm depth at 60% to 80%, and topdressing and irrigation should be carried out simultaneously; When the celery stalks reach a height of 25-30cm, remove the bottom 2-3 leaves of the sunflower. When the sunflower plant reaches a height of 80-100cm, remove the bottom 2-3 leaves. When a sunflower plant grows to a height of 110-130cm, remove the bottom 2-3 leaves. If a sunflower branch is pruned more than 3 times during its entire growth period, it should be removed immediately upon discovery. Spray 30 kg / 667 m² of 68.75% fluopyram·cymoxanil suspension at 800 times dilution and 30 kg / 667 m² of 46% copper hydroxide water-dispersible granules at 1500 times dilution every 7 days. Do not apply 15 days before celery harvest. (vi) Celery harvesting: Celery should be harvested 100-100 days after transplanting or when the celery plants reach a height of 55-65cm. (vii) Field management of sunflowers: After the celery is harvested, the sunflowers are irrigated regularly to keep the relative moisture content of the soil at a depth of 1-40cm between 55% and 75%, and no chemical fertilizers are applied. Spray 30 kg / 667 m² of 68.75% fluopyram·cymoxanil suspension at 800 times dilution and 30 kg / 667 m² of 46% copper hydroxide water-dispersible granules at 1500 times dilution every 7 days. Do not apply 15 days before sunflower harvest. (viii) Sunflower harvest: Sunflowers are harvested 100-110 days after transplanting, or when the flower heads turn yellowish-brown; (ix) Returning straw to the field.

[0006] As a further technical solution of the present invention: In step (I), the land preparation and fertilization are carried out after the soil thaws, 3000-4000 kg / 667㎡ of well-rotted farmyard manure, 20-30 kg / 667㎡ of diammonium phosphate, and 15-20 kg / 667㎡ of urea are applied, and then the soil is deeply tilled with a rotary tiller to a depth of more than 30 cm and the land is leveled.

[0007] As a further technical solution of the present invention: In step (ii), the mulch film is laid using a mulch film laying and drip irrigation integrated machine. The mulch film is 1.7m wide and 0.1mm thick white mulch film. There are 4 drip irrigation tapes laid under each mulch film. The spacing between drippers on each drip irrigation tape is 25cm. The spacing between adjacent mulch films is 14-15cm. The mulch film is compacted with soil every 60-70cm on both sides.

[0008] As a further technical solution of the present invention: the celery is selected from cold-resistant varieties; the sunflower is selected from varieties with an average growth period of 110-120 days, a plant height of 100-140cm, and 18-25 leaves.

[0009] As a further technical solution of the present invention: In the field management of the symbiotic period in step (v), the type and amount of topdressing fertilizer is 10kg to 15kg / 667㎡ of diammonium phosphate, or 8kg to 10kg / 667㎡ of ternary compound fertilizer.

[0010] As a further technical solution of the present invention: in step (nine) straw return to the field, after the sunflower heads are harvested, concentrated biogas slurry is sprayed on a cloudy morning to provide nitrogen source for the reproduction of probiotics. The amount of concentrated biogas slurry sprayed is 20kg to 30kg / 667㎡. Immediately after spraying, use a straw crushing and deep plowing machine to crush the straw to 2-5cm, mix it with Bacillus subtilis and plow it into the ground to a depth of 40cm. The amount of Bacillus subtilis used is 1kg-1.5kg / 667㎡. After returning straw to the field, irrigate 1-2 times before the freezing period, depending on the rainfall, to keep the relative moisture content of the soil at 1-40cm depth between 60% and 90%.

[0011] The beneficial effects of this invention are: Based on the soil characteristics and environmental conditions of celery-continuous cropping fields in northern regions, this invention proposes an intercropping system of celery and sunflowers. This system reduces secondary soil salinization, increases soil organic matter and beneficial bacteria, and simultaneously increases yield per unit area. In this method for improving soil conditions in celery-continuous cropping fields in northern regions, celery varieties with strong cold resistance and high yields are preferred, such as Ventura, California King, Queen, and Imperial Princess. Sunflower varieties with short growth periods, short stalks, high yields, and strong adaptability are preferred, such as Dwarf Head 567DW, American Sunflower 767DW, and New Sunflower Mixed No. 5.

[0012] Celery has a shallow root system with a relatively small root range, mostly distributed within the top 7-30cm of soil, with the majority of the root system located in the top 7-10cm layer. This limited root zone restricts the absorption of effective nutrients, and excess nutrients are leached into the topsoil layer, leading to significant salt accumulation. Sunflowers, on the other hand, have a well-developed root system. The taproot typically grows to a depth of 1.5-2m, and lateral roots usually reach a depth of 0.8-1m. Most of the root system is concentrated in the topsoil layer (0-40cm), effectively intercepting and absorbing excess nutrients.

[0013] Intercropping celery and sunflowers utilizes the vertical difference in root distribution between the shallow roots of celery and the deep roots of sunflowers. Planting them in a triangular pattern, with varying plant spacing, also creates a horizontal difference in nutrient distribution, effectively avoiding competition for soil nutrients during their co-cultivation period. Celery is generally harvested when it reaches 60-70cm in height, while sunflowers typically reach 100-140cm. Celery prefers cool temperatures and is cold-hardy but intolerant of heat. By staggering the planting times, the sunflowers only provide shade to the celery later in its growth phase, without affecting yield. Nutrients absorbed by the sunflowers are incorporated into the topsoil through straw crushing and deep tillage with beneficial soil bacteria, forming organic matter that is slowly released later. This method reduces secondary soil salinization while increasing soil organic matter and beneficial bacteria, achieving soil improvement in celery-continuous cropping areas and possessing significant potential for widespread application. Attached Figure Description

[0014] Figure 1 A schematic diagram of a sunflower arrangement for celery; Figure 2 Specific data on the physicochemical properties of the treatment and control areas.

[0015] In the diagram: 1-Drip irrigation tape, 2-Celery planting hole, 3-Celery row spacing, 4-Celery plant spacing, 5-Sunflower planting hole, 6-Sunflower row spacing, 7-Sunflower plant spacing. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Reference Figure 1 A method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers is characterized by the following steps: (a) Land preparation and fertilization: After the soil thaws, apply 3000-4000 kg / 667㎡ of well-rotted farmyard manure, 20-30 kg / 667㎡ of diammonium phosphate, and 15-20 kg / 667㎡ of urea. Then, use a rotary tiller to deeply till the soil to a depth of more than 30 cm and level the land.

[0018] (II) Laying drip irrigation tape under film: Using a film laying drip irrigation integrated machine, on the prepared ground, select white film with a width of 1.7m and a thickness of 0.1mm. Under each film, lay 4 strips of drip irrigation tape with a drip head spacing of 25cm at equal intervals of 46cm. The spacing between adjacent films is 14-15cm. The film is compacted with soil every 60-70cm on both sides.

[0019] (III) Setting the plant spacing: Determine the celery hole 2 at a distance of 11-12cm from both sides of the drip irrigation tape 1, then the celery row spacing 3 is 22-24cm, and the celery plant spacing 4 is also determined to be 22-24cm, with a seedling density of 11,000-12,500 plants per mu. Every two rows of celery, a sunflower hole 5 is determined in the center of four celery plants. The sunflower row spacing 6 is 44-48cm, and the sunflower plant spacing 7 is also determined to be 44-48cm. The number of seedlings per mu is 2800-3200. The sunflowers and celery are distributed in a triangular pattern with a row spacing of 11-12cm.

[0020] Variety selection: Celery is generally selected from cold-resistant varieties suitable for northern regions; sunflowers are selected from varieties with an average growth period of 110-120 days, a plant height of 100-140cm, and 18-25 leaves.

[0021] (iv) Staggered planting: In most parts of the north, celery can be planted in early May after the frost period. Select seedlings with 5 to 6 true leaves for planting. Irrigate immediately after planting to make the relative moisture content of the soil at 1 to 40 cm reach 80% to 90% to facilitate seedling establishment. Sunflowers can be planted 30-40 days after celery is transplanted. Select seedlings with 2-3 true leaves for transplanting. Irrigate immediately after planting to ensure that the relative moisture content of the soil at a depth of 1-40cm reaches 80%-90%, which will help the seedlings recover.

[0022] (V) Field management during the co-existence period: During the co-existence period of celery and sunflower, irrigate 3 to 5 times according to rainfall, always keeping the relative moisture content of the soil at 1 to 40 cm depth at 60% to 80%. Topdressing should be carried out at the same time as irrigation, with each topdressing being 10 kg to 15 kg of diammonium phosphate per 667 m², or 8 kg to 10 kg of compound fertilizer per 667 m². When the celery plant reaches a height of 25-30cm, remove the bottom 2-3 leaves of the sunflower; when the sunflower plant reaches a height of 80-100cm, remove the bottom 2-3 leaves; when the sunflower plant reaches a height of 110-130cm, remove the bottom 2-3 leaves; throughout the entire growth period of the sunflower, prune off the side shoots at least 3-4 times, and remove any new branches immediately. Spray 30 kg / 667 m² of 68.75% fluopyram·cymoxanil suspension at 800 times dilution and 30 kg / 667 m² of 46% copper hydroxide water-dispersible granules at 1500 times dilution every 7 days. Do not apply any more than 15 days before celery harvest.

[0023] (vi) Celery harvesting: Celery should be harvested 100-100 days after transplanting or when the celery plants reach a height of 55-65cm.

[0024] (vii) Field management of sunflowers: After the celery is harvested, irrigation can be carried out according to the rainfall. Sunflowers should be irrigated regularly to keep the relative moisture content of the soil at 1-40cm depth at 55%-75%. No more chemical fertilizers should be applied. Spray 30 kg / 667 m² of 68.75% fluopyram·cymoxanil suspension at 800 times dilution and 30 kg / 667 m² of 46% copper hydroxide water-dispersible granules at 1500 times dilution every 7 days. Do not apply any more than 15 days before sunflower harvest.

[0025] (viii) Sunflower harvest: Harvest 100-110 days after transplanting, or when the flower head turns yellowish-brown.

[0026] (ix) Straw return to the field: After the sunflower heads are harvested, spray 20-30 kg / 667㎡ of concentrated biogas slurry on a cloudy morning to provide nitrogen source for the reproduction of probiotics. Immediately after spraying, use a straw crushing and deep plowing machine to crush the straw to 2-5 cm and mix it with Bacillus subtilis (1-1.5 kg / 667㎡) and plow it into the ground to a depth of 40 cm. After straw return to the field, irrigate 1-2 times before the freezing period according to the rainfall, and always keep the relative moisture content of the soil at 1-40 cm between 60% and 90%. Detailed Implementation Example 1

[0028] The experiment was conducted in March 2021 in Xianfeng Village, Neiguan Town, Anding District, Dingxi City. The celery variety used was Ventura, and the sunflower variety was Dwarf Head 567DW. The experimental area was 3 mu (approximately 0.2 hectares), with half of it being a celery-sunflower intercropping treatment area and the other half being a celery-only control area. The specific methods are as follows: (1) On March 28, 2021, 3500 kg / 667㎡ of well-rotted farmyard manure, 25 kg / 667㎡ of diammonium phosphate and 15 kg / 667㎡ of urea were applied to the treatment area and the control area at the same time. Then, the soil was deeply tilled with a rotary tiller to a depth of more than 30 cm and the land was leveled.

[0029] (2) On April 30, 2021, both the treatment area and the control area were simultaneously covered with a drip irrigation machine. On the prepared ground, a white film with a width of 1.7m and a thickness of 0.1mm was selected. Under each film, four drip irrigation tapes with a drip head spacing of 25cm were evenly laid at equal intervals of 46cm. A gap of 14-15cm was left between the films. The film was compacted with soil every 60-70cm on both sides.

[0030] (3) On May 2, 2021, celery seedlings with 5-6 true leaves were selected simultaneously from both the treatment and control areas and planted at a spacing of 23* Plant at 23cm height, and irrigate immediately after planting to ensure the relative moisture content of the soil at a depth of 1-40cm reaches 85%. Irrigate again on May 25th. Additionally, apply 10 kg / 667 m² of diammonium phosphate as a top dressing. On June 10th, in the control area, plant celery every two rows, centering on four celery plants according to plant spacing. Distance 46 *46cm (reference) Figure 1 Select sunflower seedlings with 2-3 true leaves for transplanting. Irrigate immediately after planting to ensure that the relative moisture content of the soil at a depth of 1-40cm reaches 85%.

[0031] (4) The treatment area and the control area were irrigated once on June 25 and topdressed with 8 kg / 667㎡ of compound fertilizer. The bottom 2 leaves of the sunflower in the treatment area were removed on June 28. The treatment area and the control area were irrigated once on July 12 and topdressed with 10 kg / 667㎡ of diammonium phosphate. The bottom 3 leaves of the sunflower in the treatment area were removed on July 16. The treatment area and the control area were irrigated once on July 26 and topdressed with 8 kg / 667㎡ of compound fertilizer. The bottom 2 leaves of the sunflower in the treatment area were removed on July 30. The treatment area and the control area were sprayed alternately every 7 days with 30 kg / 667㎡ of 800 times dilution of 68.75% fluopyram·cymoxanil suspension and 30 kg / 667㎡ of 1500 times dilution of 46% copper hydroxide water-dispersible granules. No application was made 15 days before the harvest of celery and sunflower.

[0032] (5) Celery in the treatment area was harvested on August 10, and celery in the control area was harvested on August 15. The treatment area was irrigated twice on August 17 and September 7, and no fertilizer was applied. The sunflowers in the treatment area were harvested on September 28.

[0033] (6) On October 1, on a cloudy morning, 20 kg of concentrated biogas slurry per 667 m² (provided by Gansu Longkangyuan Organic Agriculture Technology Development Co., Ltd.) was sprayed onto sunflower straw. Immediately after spraying, the straw was crushed to 2-5 cm using a straw crushing and deep plowing machine. It was then mixed with 1.5 kg of Bacillus subtilis per 667 m² and plowed into the ground to a depth of 40 cm. Irrigation was carried out once on October 12 and once on October 26.

[0034] Yields were measured after celery and sunflower harvests. In April of the following year, the soil in both treatment and control areas was rotary tilled to a depth of 40 cm, and its physicochemical properties were measured. Specific data are referenced below. Figure 2The results of the example experiment showed that, compared with single-cropping of celery, intercropping celery with sunflower resulted in a 0.91% decrease in celery yield per mu (unit of land area), which was not significant; a 14.38% decrease in total soil salinity, which was significant; and a 12.13% increase in soil organic matter, which was also significant.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers, characterized in that: comprises the following steps: (1) Land preparation and fertilization; (2) Laying mulching film and drip irrigation tapes (1): laying mulching film on the prepared land, and uniformly laying drip irrigation tapes (1) under the mulching film at an equal spacing of 46 cm; (3) Setting plant spacing and row spacing: determining celery hole sites (2) at 11 to 12 cm on both sides of each drip irrigation tape (1), wherein the row spacing (3) of celery is 22 to 24 cm, and the plant spacing (4) of celery is 22 to 24 cm; determining sunflower hole sites (5) at the center of four celery plants after every two rows of celery, wherein the row spacing (6) of sunflowers is 44 to 48 cm, and the plant spacing (7) of sunflowers is also 44 to 48 cm; (4) Staggered-period planting: celery can be planted after the end of the frost period in northern regions, a cold-tolerant variety is selected for celery, celery seedlings with 5 to 6 true leaves are selected for planting, and irrigation is performed immediately after planting, so that the relative water content of soil at a depth of 1 to 40 cm reaches 80% to 90%, which facilitates seedling recovery; Generally, 30 to 40 days after celery planting, sunflowers are planted. A variety with an average growth period of 110 to 120 days, a plant height of 100 to 140 cm and 18 to 25 leaves is selected for sunflowers, sunflower seedlings with 2 to 3 true leaves are selected for planting, and irrigation is performed immediately after planting, so that the relative water content of soil at a depth of 1 to 40 cm reaches 80% to 90%, which facilitates seedling recovery; Through interplanting cultivation of celery and sunflowers, the difference in vertical distribution in soil formed by the shallow root system of celery and the deep root system of sunflowers is utilized, and through planting the two crops in a "pin-shaped" distribution, the difference in horizontal distribution is also formed by utilizing the plant spacing and row spacing, thereby effectively avoiding competition for soil nutrient absorption between the two crops during the symbiotic period; (5) Field management during the symbiotic period: irrigation is performed 3 to 5 times during the symbiotic period of celery and sunflowers, the relative water content of soil at a depth of 1 to 40 cm is always maintained at 60% to 80%, and topdressing is performed simultaneously with irrigation; when the plant height of celery reaches 25 to 30 cm, 2 to 3 of the lowest leaves of sunflowers are removed; when the plant height of sunflowers reaches 80 to 100 cm, 2 to 3 lower leaves of the sunflowers are removed; when the plant height of sunflowers reaches 110 to 130 cm, 2 to 3 lower leaves of the sunflowers are removed; suckering is removed more than 3 times during the whole growth period of sunflowers, and any sunflower branch is removed immediately once found; 68.75% fluopicolide·propamocarb suspension concentrate with an 800-fold dilution at 30 kg per 667 m² and 46% copper hydroxide water dispersible granule with a 1500-fold dilution at 30 kg per 667 m² are alternately sprayed every 7 days, and application is stopped 15 days before celery harvesting; (6) Celery harvesting: harvesting is performed timely 100 to 100 days after celery planting or when the plant height of celery reaches 55 to 65 cm; (7) Field management of sunflowers: after celery harvesting, sunflowers are irrigated regularly to keep the relative water content of soil at a depth of 1 to 40 cm at 55% to 75%, and no chemical fertilizer is applied any more; 68.75% fluopicolide·propamocarb suspension concentrate with an 800-fold dilution at 30 kg per 667 m² and 46% copper hydroxide water dispersible granule with a 1500-fold dilution at 30 kg per 667 m² are alternately sprayed every 7 days, and application is stopped 15 days before sunflower harvesting; (8) Sunflower harvesting: harvesting is performed 100 to 110 days after sunflower planting or when the flower disc turns yellowish brown; (9) Straw returning to the field.

2. The method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers according to claim 1, characterized in that: In step (I), the land preparation and fertilization involves applying 3000-4000 kg / 667㎡ of well-rotted farmyard manure, 20-30 kg / 667㎡ of diammonium phosphate, and 15-20 kg / 667㎡ of urea after the soil has thawed. Then, the soil is deeply tilled with a rotary tiller to a depth of more than 30 cm, and the land is leveled.

3. The method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers according to claim 1, characterized in that: In step (ii), a film-laying and drip irrigation integrated machine is used for laying the mulch film. The mulch film is 1.7m wide and 0.1mm thick white mulch film. Four drip irrigation tapes are laid under each mulch film. The spacing between drippers on each drip irrigation tape is 25cm. The spacing between adjacent mulch films is 14-15cm. The soil is compacted every 60-70cm on both sides of the mulch film.

4. The method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers according to claim 1, characterized in that: In step (v) of the symbiotic period, the type and amount of topdressing are 10-15 kg / 667㎡ of diammonium phosphate or 8-10 kg / 667㎡ of compound fertilizer.

5. A method for improving soil in celery-continuous cropping fields in northern regions by intercropping sunflowers, as described in claim 1, characterized in that: In step (ix) of straw return to the field, after the sunflower heads are harvested, concentrated biogas slurry is sprayed on a cloudy morning to provide nitrogen source for the reproduction of probiotics. The amount of concentrated biogas slurry sprayed is 20kg to 30kg / 667㎡. Immediately after spraying, use a straw crushing and deep plowing machine to crush the straw to 2-5cm, mix it with Bacillus subtilis and plow it into the ground to a depth of 40cm. The amount of Bacillus subtilis used is 1kg-1.5kg / 667㎡. After returning straw to the field, irrigate 1-2 times before the freezing period, depending on the rainfall, to keep the relative moisture content of the soil at 1-40cm depth between 60% and 90%.

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