An efficient seedling cultivation method for *Hemiberlesia lataniae*

Abstract

This invention discloses a highly efficient seedling cultivation method for *Heliotropium indicum*, comprising the following steps: A. Seed collection and preparation: separating achenes and seed coating; B. Seedbed preparation: sequentially spreading well-rotted organic material and compound fertilizer on the seedbed; C. Seed dressing and sowing; D. Field management: watering and weeding, transplanting after 2-3 months. This invention is simple to operate, uses locally sourced materials, has low cost, produces uniform seedlings with high germination and emergence rates, robust seedlings, and high transplant survival rates. It solves the problem of unstable yields due to various factors in the wild state, providing a source guarantee for stable yield and controllable quality. This technology is easy to promote and has high social value.

Description

Technical Field

[0001] This invention relates to the field of *Hemiberlesia lataniae* seedling cultivation, and in particular to a highly efficient seedling cultivation method for *Hemiberlesia lataniae*. Background Art

[0002] Carpesium cernuum L., a plant in the Asteraceae family, is one of the plant sources of the traditional Chinese and ethnic medicinal herb, wild tobacco leaves. Wild tobacco leaves are bitter and pungent in taste, and cool in nature. They have the functions of clearing heat and detoxifying, reducing swelling and relieving pain. They are used for colds with fever, sore throat, toothache, boils and carbuncles. It is a major ingredient in Guizhou Bailing Shuangyang Houbitong Granules.

[0003] Wild tobacco is a niche, less-known variety, primarily supplied through wild cultivation. Currently, there are no artificial cultivation bases in China, and no reports on domestication and seedling cultivation techniques are available. Research only reveals studies on medicinal quality testing. To domesticate wild tobacco, a large quantity of high-quality seedlings is essential. Traditional crop seedling cultivation is time-consuming and complex, and the small size of the seeds leads to high germination density after sowing, making seedlings susceptible to scorching from later fertilization. Therefore, there is an urgent need to develop a highly efficient seedling cultivation method for wild tobacco that shortens the cultivation cycle, simplifies management, and produces robust seedlings. Summary of the Invention

[0004] The purpose of this invention is to provide an efficient seedling cultivation method for *Hemiberlesia lataniae*. This invention features a short seedling cycle, simple management process, robust seedlings, and low cost.

[0005] The technical solution of this invention: A highly efficient seedling cultivation method for *Hemiberlesia lataniae*, comprising the following steps:

[0006] A. Seed collection and preparation: In mid-to-late September, when the seeds are mature, take the whole capitulum with stems and branches shorter than 10cm, dry it in the sun, break it open by hand to remove the bracts, miscellaneous leaves and dead branches, separate the small achenes from the dried capitulum, dry it until the seeds have a safe moisture content, store it in a breathable burlap bag in a well-ventilated room, and coat the seeds of *Hemiberlesia lataniae* with a seed coating agent before sowing.

[0007] B. Seedbed preparation: Remove all kinds of debris from the nursery plot, thoroughly disinfect and sterilize, deep plow the land to 20-30cm, and divide the soil into beds 1.0-1.2m wide. Using the operation ditch as the horizontal reference, loosen the soil on both sides of the bed surface. The first layer is a layer of decomposed medicinal residue, the second layer is a layer of evenly spread decomposed sheep manure, and the third layer is a layer of evenly spread compound fertilizer. Then, cover the bed surface with the loosened soil and water it thoroughly.

[0008] C. Seed dressing and sowing: From late September to March of the following year, mix seeds with 0.025–0.03 mg of a suitable solution per 1 kg of seeds. 3 After thoroughly mixing with the humus, the seeds are sown immediately.

[0009] D. Field management: Water and weed in a timely manner after sowing. Seedlings can be transplanted after growing for 2-3 months.

[0010] In the aforementioned efficient seedling raising method for *Heliotropium indicum*, in step A, the safe seed moisture content is 9%–12%. The seed coating is performed by using 26% thiamethoxam·cypermethrin·cymoxanil suspension seed coating agent at a dosage of 6–7.4g per 1kg. The agent is measured, diluted with an appropriate amount of water, and stirred evenly to form a slurry. The seeds are then poured into the slurry, stirred thoroughly, and dried before sowing.

[0011] In the aforementioned efficient seedling cultivation method for *Heliotropium indicum*, step B, the thorough disinfection and sterilization, involves uniformly spraying the nursery plot and surrounding areas, as well as the well-rotted medicinal residue and well-rotted sheep manure, with a 29% lime-sulfur mixture diluted 40 times with water. The well-rotted medicinal residue is obtained by pharmaceutical companies from the extraction of traditional Chinese medicine, and is naturally piled up and fermented for more than one year. When the center temperature of the residue pile is the same as or slightly higher than the ambient temperature and there is no foul odor, it is considered well-rotted. The thickness of the spread is 4-6 cm. The well-rotted sheep manure is purchased from farmers and is fully decomposed through traditional piling. Its dosage is 200-300 kg / mu. The compound fertilizer contains N≥15%, P2O5≥15%, K2O≥15%, and total nutrients≥45%, and its dosage is 10-20 kg / mu.

[0012] In the aforementioned efficient seedling raising method for *Heliotropium indicum*, in step C, the sowing amount is 2-3 kg per mu (approximately 0.067 hectares), the sowing amount on the seedbed is calculated in advance, and the sowing is carried out in 3 times.

[0013] In the aforementioned efficient seedling cultivation method for *Heliotropium indicum*, step D, timely watering, means replenishing water in a timely manner to maintain the moisture content of the seedbed at 12%–18%, and weeding, means manually weeding once during the entire seedling period when *Heliotropium indicum* is at the two-leaf stage.

[0014] Compared with existing technologies, firstly, before sowing, this invention abandons traditional seedbed preparation methods. It utilizes well-rotted medicinal residue obtained from the applicant's pharmaceutical extraction as a base layer. This residue is loose, lightweight, and free of weeds, pathogens, and insect eggs, thus turning waste into valuable recycled materials and improving the seedbed's properties, resulting in better permeability and a more favorable environment for the growth of *Hemiberlesia lataniae* roots. Then, a second layer of well-rotted sheep manure is evenly spread, followed by a third layer of compound fertilizer. Finally, the loosened soil is covered back onto the seedbed. This provides the basic seedbed with safe and sufficient fertilizer, supplying the necessary nutrients for *Hemiberlesia lataniae* throughout its seedling stage. After emergence, no additional fertilization is needed to ensure robust seedlings. Besides reducing labor costs in later operations, this invention also avoids losses caused by fertilizer burn or mechanical damage to seedlings during later application.

[0015] Secondly, because the seeds of *Heliotropium indicum* are small, this invention separates the small achenes from the inflorescence and mixes them with 0.025–0.03 mg of [a specific ingredient] per 1 kg of seeds. 3 After thoroughly mixing with humus, sow the seeds in three stages to ensure even seedling density. This prevents some seedlings from growing in clusters while others fail to emerge, thus reducing the seedling failure rate and increasing the seedling survival rate. This ensures robust seedling growth after emergence, improving the survival rate and seedling vigor. The yield of *Heliotropium indicum* seedlings can reach 100,000 to 120,000 plants per acre, with a transplant survival rate of over 90%.

[0016] Meanwhile, before sowing, this invention employs seed coating and a series of treatments, including thorough disinfection of the nursery plot and surrounding areas with well-rotted medicinal residue and sheep manure. These measures create an environment conducive to the growth and development of *Hemiberlesia lataniae* (a type of medicinal herb) while inhibiting the breeding and reproduction of harmful organisms. This minimizes or eliminates potential losses from pests and diseases, and avoids the side effects and environmental impacts of applying pesticides during the seedling stage, thus better meeting the green technology requirements for medicinal herb production. The auxiliary materials used in this invention, such as well-rotted medicinal residue and sheep manure, are readily available locally and can be applied to a wide range of growers. Therefore, this *Hemiberlesia lataniae* seedling cultivation method can be widely promoted and has high social value.

[0017] In summary, the present invention's method for cultivating Tobacco Botanical Seedlings transforms the original wild-grown natural growth into artificial seedling cultivation. This ensures consistent management of Tobacco Botanical Seedlings at all growth stages, allowing the scale of seedling cultivation to be determined according to production plans. This guarantees stable and controllable quantity and quality of seedlings, avoiding the problems of inconsistent yields and plant sizes that have long relied on the wild natural state. This provides pharmaceutical companies with a stable and controllable source of production for pharmaceutical production using wild tobacco leaves as raw materials. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0019] Example. This invention addresses the issue of unstable yield and quality of wild tobacco leaves under natural conditions, which cannot meet the large-scale demand for stable and controllable high-quality seedlings during the domestication process. The specific seedling raising steps are as follows:

[0020] Seed collection and preparation: In mid-to-late September, when the seeds are mature, remove the entire capitulum with stems and branches shorter than 10cm, dry it in the sun, break it open by hand to remove the bracts, miscellaneous leaves and dead branches, separate the small achenes from the dried capitulum, dry it until the seeds reach a safe moisture content, store it in a breathable burlap bag in a well-ventilated room, and coat the seeds with a seed coating agent before sowing.

[0021] The seeds of *Heliotropium indicum* are tiny and densely distributed within its capitulum (flower heads) to mature. It is necessary to separate the small achenes from the dried capitulum to prevent clustered germination and seedling stunting. After separation, the seeds should be dried to a safe moisture content of 9%–12%. Before sowing, use a 26% thiamethoxam·cypermethrin·cymoxanil suspension seed dressing agent at a dosage of 6–7.4g per kg of seed dressing. Measure the agent, dilute it with an appropriate amount of water, and stir well to form a slurry. Pour the slurry into the slurry, stir thoroughly, and allow it to dry before sowing.

[0022] B. Seedbed preparation: Remove all kinds of debris from the nursery plot, thoroughly disinfect and sterilize, deep plow the soil to 20-30cm, and divide the soil into beds 1.0-1.2m wide. Using the operation channel as the horizontal reference, loosen the soil on both sides of the bed surface. The first layer is a layer of decomposed medicinal residue, the second layer is a layer of evenly spread decomposed sheep manure, and the third layer is a layer of evenly spread compound fertilizer. Then, cover the bed surface with the loosened soil and water it thoroughly.

[0023] The decomposed medicinal residue here is the residue obtained by pharmaceutical companies after extracting traditional Chinese medicine. It is naturally piled up and fermented for more than a year. When the center temperature of the residue pile is the same as or slightly higher than the ambient temperature and there is no foul odor, it is considered decomposed medicinal residue. Its spread thickness is 4-6cm. The decomposed sheep manure here can be purchased from farmers. The sheep manure is fully decomposed through traditional piling. Its usage is 200-300kg / mu. The compound fertilizer here contains N≥15%, P2O5≥15%, K2O≥15% and total nutrients≥45%. Its usage is 10-20kg / mu.

[0024] Both the dregs of medicinal herbs and sheep manure must be fully decomposed. When using them, spray the nursery plot and surrounding area with a 29% lime-sulfur mixture diluted 40 times with water. This creates an environment conducive to the growth and development of *Hedysarum heterotropoides*, while inhibiting the breeding and reproduction of various harmful organisms. This minimizes or eliminates potential losses from pests and diseases, and avoids the side effects and environmental impacts of applying pesticides during the seedling stage, thus better meeting the green technology requirements for medicinal herb production. The decomposed dregs are loose, lightweight, and free of weeds, pathogens, and insect eggs. This allows for the recycling of waste materials and improves the properties of the seedbed, enhancing its permeability and providing a more favorable environment for the root growth of *Hedysarum heterotropoides*. Then, a second layer of well-rotted sheep manure is evenly spread, followed by a third layer of compound fertilizer. Finally, the loosened soil is covered back onto the seedbed surface. This ensures that the basic seedbed has safe and sufficient fertilizer, providing the necessary nutrients for the *Hedysarum heterotropoides* throughout the seedling stage. It also ensures that the seedlings are strong without additional fertilization. In addition to reducing the labor costs of later operations, it can also avoid losses caused by fertilizer burn or mechanical damage to the seedlings.

[0025] C. Seed dressing and sowing: From late September to March of the following year, mix seeds with 0.025–0.03 mg of seed dressing solution per 1 kg of seeds. 3 After thoroughly mixing with the humus, the seeds are sown immediately. A spacing of 0.025m is preferred. 3 .

[0026] The sowing rate here is 2-3 kg per mu (approximately 0.16 acres). The sowing amount on the seedbed should be calculated in advance, and the seeds should be sown in three stages. This effectively reduces the seedling emergence rate, increases the seedling survival rate, and ensures that the seedlings grow vigorously after emergence. It can improve the survival rate and seedling strength, achieving a yield of 100,000-120,000 seedlings per mu (approximately 16,000-120,000 per acre), with a transplant survival rate of over 90%.

[0027] D. Field management: Water and weed in a timely manner after sowing. Seedlings can be transplanted after growing for 2-3 months.

[0028] The timely watering here refers to replenishing water promptly to maintain the seedbed moisture content at 12%–18%. Weeding here refers to manual weeding once during the entire seedling period when the *Heliotropium indicum* reaches the two-leaf stage. This invention's seedling cultivation method, combined with the biological characteristics of *Heliotropium indicum*, integrates pest and disease control and nutrient supply into a single pre-sowing treatment of the seedbed and seedling materials. Seedlings can emerge from the nursery in as little as two months, thus avoiding the tedious post-emergence field management process and achieving highly efficient seedling cultivation.

[0029] In this invention, the fermented medicinal residue is obtained from the production of traditional Chinese medicines such as Yindan Xinnaotong soft capsules, Vitamin C Yinqiao tablets, Kesuting syrup and capsules, and Jingan capsules. This residue is naturally piled and fermented for over a year. Fermented residue is considered mature when the center temperature of the pile is the same as or slightly higher than the ambient temperature and there is no foul odor. The fermented sheep manure is sheep manure that has been fully fermented through traditional piling and can be purchased from farmers. Compound fertilizer and pesticides are commercially available products and can be purchased from agricultural supply stores. The material costs of this invention are low, therefore this efficient seedling cultivation method for *Heliotropium indicum* can be widely promoted and has high social value.

[0030] Different fertilization methods for *Hemiberlesia lataniae* seedling cultivation were compared in an experiment conducted on September 23, 2023. Using the four methods listed in Table 1, *Hemiberlesia lataniae* seeds were uniformly treated and sown in the same plot. The experiment employed a randomized block design, with each fertilization method having three replicates. Each replicate consisted of four plots (1m x 8m each). Field growth (seedling condition and weed status) after fertilization and the number of qualified seedlings two months after sowing were used as evaluation indicators. Good field growth was characterized by vibrant green *Hemiberlesia lataniae* seedlings, robust growth, no abnormalities, and weak weeds. Qualified seedlings were defined as: seedling length 12–20cm, root length 5–15cm, and more than 5 leaves.

[0031] The number of taproots should be greater than 5, with a higher number of qualified seedlings being preferred. The results are as follows:

[0032]

[0033] Note: (1) Different lowercase (uppercase) letters in the same column indicate significant differences (p=0.05) or extremely significant differences (p=0.01).

[0034] (2) The theoretical yield per mu is based on 500m³. 2 The effective seedling area is calculated.

[0035] A comparative experiment on different fertilization methods for *Heliotropium indicum* seedling cultivation revealed that during the seedling growth period, Treatment A provided sufficient basic nutrition, resulting in robust seedlings with normal, healthy leaf color. Only one weeding was needed during the growing season, after which *Heliotropium indicum* could compete with weeds and form a dominant population, requiring no further weeding. Treatment B, after topdressing, saw rapid seedling growth, but weeds also grew simultaneously, exhibiting less robust growth and faster weed growth compared to Treatment A. Treatment C, after applying urea, caused varying degrees of seedling burn on the plant surfaces, and resulted in numerous weeds. Treatment D showed no significant seedling growth and had many weeds. At the final emergence, Treatment A yielded an average of 1914 qualified seedlings per plot, equivalent to a theoretical yield of 119,667 seedlings per mu (approximately 0.16 acres). The yields of the other treatments were significantly lower than those of the patented technology, with statistically significant and highly statistically significant differences. This demonstrates the significant technical effect of the patented technology on seedling production.

[0036] A comparative experiment was conducted to compare the pest and disease control methods of *Hemiberlesia lataniae* seedling cultivation. Two treatment groups were set up in the same plot. Treatment A: Before sowing, 26% thiamethoxam·cypermethrin·cymoxanil suspension seed coating agent was used at a ratio of 6-7.4g per kg of *Hemiberlesia lataniae* seeds for seed coating. The nursery plot, surrounding areas, well-rotted pesticide residue, and well-rotted sheep manure were uniformly sprayed with a disinfectant solution of 29% lime sulfur solution diluted 40 times with water. Treatment B: No pesticide treatment was used before sowing. At 15, 30, and 45 days after sowing, the occurrence of pests and diseases was investigated using a diagonal five-point sampling method. The area of ​​each sample plot was 1m². 2 The fewer the occurrence of pests and diseases, the better. The results are as follows:

[0037]

[0038] Note: (1) Different lowercase (uppercase) letters in the same column indicate significant differences (p=0.05) or highly significant differences (p=0.01).

[0039] As shown in Table 4, the patented technology effectively prevented pests and diseases. No pests or diseases were observed 15 days after sowing. At 30 days, notches appeared on the plants, indicating pest infestation. The incidence rate in treatment A was lower than in treatment B. At this point, leaf spot disease was observed in treatment B, but not in treatment A. At 45 days, pests and diseases were observed in both groups, but the incidence rate and disease index in treatment A were significantly lower than in treatment B. Therefore, this patented technology effectively prolonged the leaf spot disease cycle, reduced the incidence of leaf spot disease, and decreased the incidence of notches caused by pests.

[0040] A comparative experiment was conducted on different sowing methods for *Hedychium diffusa* seedling cultivation. On September 23, 2023, different gradient treatments were used: Treatment A: no seed dressing, direct broadcasting; Treatment B: 0.015–0.02 m³ of seed dressing was applied per 1 kg of seeds. 3 After thoroughly mixing with humus, sow the seeds all at once; Treatment C: Mix 0.025–0.03 m³ of the mixture with every 1 kg of seeds. 3 After thoroughly mixing with humus, sow the seeds in three batches; Treatment D: Mix 0.035–0.04 m³ of the mixture with each 1 kg of seeds. 3 After thorough mixing with humus, seeds were sown in four separate applications; all other management procedures were consistent. Each treatment was replicated three times. A total of 12 seed portions, each weighing 10g, were collected (considering the extremely small size of *Hedysarum heterotropoides* seeds, making it difficult to accurately count them in the field, the same amount of seeds was used in the experiment to avoid human error). A randomized block design was used to divide the experimental plots, with each plot measuring 1m². 2 Based on randomly selected numbers corresponding to different plots, seeds were treated with different methods and then broadcast onto seedbeds. The number of seedlings emerging on the 5th day after initial emergence was compared.

[0041] Seedling survival rate at the time of seedling removal (number of seedlings / total number of seedlings).

[0042] Larger quantities are preferred. The results are as follows:

[0043]

[0044] Note: (1) Different lowercase (uppercase) letters in the same column indicate significant differences (p=0.05) or highly significant differences (p=0.01).

[0045] Analysis of the results in Table 5 shows significant and highly significant differences in germination and seedling establishment rates among the four different sowing methods. Direct broadcasting yielded the worst results, with poor germination and low seedling establishment rates, leading to seed waste. Treatments B and C showed little difference in germination rates, but treatment C had a significantly higher germination rate at lift-out, demonstrating a significant advantage across the four gradients. While treatment D had a high seedling establishment rate later on, the excessive use of humus in the seed dressing negatively impacted early germination, wasting seeds and increasing humus costs. Therefore, treatment C was the most effective, requiring 0.025–0.03 m³ of humus per 1 kg of seeds.3 After thoroughly mixing with humus, sow the seeds in three batches.

[0046] A comparison of the seedling cultivation method for *Hemiberlesia lataniae* at different times with wild-collected seedlings shows that seedlings can be cultivated according to this patented technology after the *Hemiberlesia lataniae* matures in mid-to-late September. Two to three months after sowing, a yield of 100,000 to 120,000 seedlings per mu (approximately 667 square meters) can be achieved, with a transplant survival rate of over 90%. The earliest batch of seedlings can be transplanted in mid-to-late November. However, the same seedling cultivation period coincides with autumn / winter and early spring in the wild. At this time, the wild environment cannot provide suitable germination conditions for *Hemiberlesia lataniae* seeds, making it impossible to collect seedlings during this period. After April, wild seedlings can begin to germinate, but the inconsistent water, air, light, heat, and fertility conditions in different habitats result in uneven growth of wild *Hemiberlesia lataniae* seedlings, making it impossible to carry out standardized planting and management according to the grading standards. Therefore, this patented technology solves the long-standing predicament of relying mainly on wild tobacco leaves for supply, and addresses the primary issue in the domestication of wild tobacco—the source of high-quality germplasm. This provides a stable and quality-controllable source guarantee for the applicant's production of Shuangyang Houbitong Granules, a pharmaceutical preparation made from wild tobacco leaves.

Claims

1. A highly efficient seedling cultivation method for *Heliotropium indicum*, characterized in that, Includes the following steps: S1. Seed collection; After the seeds of the herbaceous plant mature, remove the entire capitulum of the herbaceous plant with stems and branches shorter than 10cm and dry it in the sun. Then separate the seeds of the herbaceous plant from the dried capitulum and dry them to a safe moisture content before storing them. S2. Seed preparation: Before sowing, the preserved *Heliotropium indicum* seeds are coated with a seed coating agent to obtain *Heliotropium indicum* seeds ready for sowing. S3. Seedbed preparation: Remove weeds and disinfect the land to be sown. First, spread well-rotted medicinal residue in the area to be sown, then apply fertilizer in advance, and finally cover with soil and water. S4. Seed mixing and sowing; At the suitable time for sowing *Heliotropium indicum* seeds, mix 0.025-0.03 mg of the mixture with water at a rate of 0.025-0.03 mg per 1 kg of seeds. 3 Mix the seeds with humus in a specific ratio, and then sow the seeds immediately after thorough mixing. S5. Field management: timely watering and weeding to maintain the moisture content of the seedbed at 12%–18%; transplant seedlings after 2–3 months of growth. In step S1, the safe moisture content of *Hemiberlesia lataniae* seeds is 9%–12%. In step S2, the specific operation of seed coating is as follows: use 6–7.4g of 26% thiamethoxam·pyrethroid·cymoxanil suspension seed coating agent per 1kg of *Hemiberlesia lataniae* seeds. Measure the agent, add an appropriate amount of water to dilute and stir evenly to form a slurry. Pour the *Hemiberlesia lataniae* seeds into the slurry, stir thoroughly, and let it dry before sowing. The specific process for preparing the seedbed in step S3 is as follows: First, remove all kinds of debris from the nursery plot, thoroughly disinfect and sterilize, deeply plow the land to 20-30cm, divide the soil into beds with a width of 1.0-1.2m, take the operation ditch as the horizontal reference, loosen the soil on both sides of the bed, lay the first layer of decomposed medicine residue, spread the second layer of decomposed sheep manure evenly, spread the third layer of compound fertilizer evenly, then cover the bed with the loosened soil, and water it thoroughly. The compound fertilizer contains N≥15%, P2O5≥15%, K2O≥15%, and total nutrients≥45%; the dosage is 10-20 kg / mu. In step S4, the seeding rate is 2-3 kg per mu; based on the calculated seeding rate for each bed, the seeds are sown in 3 times.

2. The efficient seedling cultivation method for *Hemiberlesia lataniae* according to claim 1, characterized in that: In step S1, the seeds of *Heliotropium indicum* mature in mid-to-late September; when storing the seeds, they should be kept in a well-ventilated indoor space using a breathable burlap bag.

3. The efficient seedling cultivation method for *Hemiberlesia lataniae* according to claim 1, characterized in that: The thorough disinfection and sterilization in step S3 involves uniformly spraying the nursery plot and its surroundings, as well as the decomposed medicinal residue and decomposed sheep manure, with a disinfectant solution diluted 40 times with 29% lime sulfur solution.

4. The efficient seedling cultivation method for *Hemiberlesia lataniae* according to claim 1, characterized in that: The aforementioned decomposed medicinal residue is the residue obtained by pharmaceutical companies after extracting traditional Chinese medicine for pharmaceutical production. It is naturally piled up and fermented for more than a year. When the center temperature of the residue pile is the same as or slightly higher than the ambient temperature and there is no foul odor, it is considered decomposed medicinal residue. The thickness of the decomposed medicinal residue is 4-6 cm.

5. The efficient seedling cultivation method for *Hemiberlesia lataniae* according to claim 1, characterized in that: The decomposed sheep manure mentioned is sheep manure purchased from farmers and fully decomposed through piling, with a dosage of 200-300 kg / mu.

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