Sunflower High-Density Planting Methods: Seed Selection Tips and the Best Sowing Time
Sunflower, also called kuihua, has seeds that can be processed into snacks or used for oil pressing. The oil residue can also be used as feed, making it one of the traditional cash crops. So how do you plant sunflowers at high density? How do you choose seeds? When is the best time to sow?
Seed Selection
1. Variety selection: Choose excellent varieties with strong stress resistance, good yield performance and suitability for the local ecological conditions, such as Gankui No. 1, Gankui No. 2, Gankui No. 3, etc., or other varieties suitable for local cultivation.
2. Seed quality: Seed purity higher than 98%, cleanliness greater than 98%, germination rate higher than 90%, and moisture content no higher than 15%.
3. Seed cleaning: 4~5 days before sowing, clean the sunflower seeds, remove mixed grains, shriveled grains and small grains, then sun the seeds for 2~3 days to increase seed vigor and improve the germination rate and germination energy.
4. Seed treatment: Before sowing, soak the seeds in warm water at 25~30°C for 3~4 hours, or soak them in cold water for 6 hours, remove and air-dry, then pile them in a place at 15~20°C for one day and one night. Once some seed coats have opened and sprouted, they can be sown.
Land Selection, Previous Crop Selection and Land Preparation
1. Land selection: Choose plots with deep topsoil, flat terrain, good drainage and rich organic matter content.
2. Previous crop selection: Cereal crops are good previous crops for sunflowers. In production, the rotation period is generally 5~7 years. Absolutely avoid continuous cropping and back-to-back cropping.
3. Land preparation
3.1 Autumn plowing and ridge formation: The suitable live soil layer is 25~30cm, plowing depth should be 20~25cm, and subsoiling 30~40cm. Achieve no missed plowing and no clods, promptly apply farmyard manure or green manure while forming ridges, and compact promptly after plowing.
3.2 Autumn plowing with spring ridge formation: On the basis of autumn plowing, when the soil thaws 14cm in early spring, promptly harrow and level, form ridges and compact, strictly preventing soil moisture loss.
3.3 Subsoiling and ridge formation: First loosen the original furrow, then break the original ridge platform to form new ridges, and compact promptly.
3.4 Rotary tillage and ridge formation: Suitable for soybean, potato, corn and millet/broomcorn millet stubble. In early spring when the soil thaws more than 14cm, carry out rotary tillage and then form ridges, and compact promptly.
Fertilization
1. Farmyard manure: Combined with land preparation, apply 30~40 cubic meters of fully decomposed high-quality farmyard manure per hectare.
2. Green manure: Combined with land preparation, apply an adequate amount of approved green manure.
3. Chemical fertilizer
3.1 Nitrogen fertilizer: At the sunflower budding stage, apply 100~150kg of urea per hectare as a top dressing. Nitrate nitrogen must not be used. The last top dressing must be carried out 30d before harvest.
3.2 Phosphate fertilizer: Apply 60~75kg of phosphorus pentoxide per hectare, incorporated during land preparation as base fertilizer or seed fertilizer.
3.3 Potassium fertilizer: Apply 35~50kg of potassium oxide per hectare, incorporated during land preparation as base fertilizer or seed fertilizer.
Timely Sowing
1. Sowing period: Sowing can begin when the temperature at 5cm in the soil layer remains stable at 8~10°C for 3~5d consecutively. In our area, this is generally May 15 to May 20.
2. Sowing method: Use manual dibbling on the ridge, or open furrows with a plow and then dibble by hand. For dry plots, dig holes and sow with water.
3. Sowing methods
3.1 Manual pre-germination hole sowing: For plots with soil moisture content below 20%, sow in holes with water; when soil moisture content is above 22%, sow directly in holes.
3.2 Mechanical precision dibbling (hill) sowing on ridges
4. Sowing depth: Sowing depth 6~7cm, keeping depth consistent, covering soil evenly, reaching 4~5cm after compaction.
5. Sowing density: Ridge spacing 65cm, plant two ridges and leave one ridge empty, plant spacing 50cm.
6. Sowing rate
6.1 Manual dibbling: Sow 3~4 seeds per hole.
6.2 Mechanical sowing: Sowing rate 12.5~15kg per hectare.
Field Management
1. Thinning: Thin the seedlings immediately when one pair of true leaves appears, and set the seedlings when two pairs of true leaves have grown, leaving one strong seedling per hole.
2. Cultivation and weeding: Three hoeings and three ridgings must be carried out. The first cultivation should be early, as soon as the seedlings have two pairs of true leaves; where conditions allow, deep loosening of the furrow should be carried out. After the first hoeing and ridging is completed, hoe and ridge once about every 10d, and promptly remove large weeds.
3. Irrigation: Irrigate timely and appropriately according to crop growth, especially during the budding stage and flowering stage, irrigate promptly when drought occurs.
4. Branch removal: The small branches growing from the leaf axils of sunflowers and the ineffective small flower heads beside the main flower head should be removed promptly.
5. Artificial pollination: Use a powder puff made of soft gauze, cotton or sponge to gently tap the flower heads in sequence after the morning dew has dried. Bees can also be used for supplementary pollination, with 15 hives placed per hectare.
6. Control of diseases, pests, and weeds
6.1 Control of Sclerotinia rot: A rotation of more than 5 years can be adopted, together with chemical control. Use 0.5% of seed weight of quintozene or 0.5% of seed weight of dimethachlon for seed dressing.
6.2 Control of brown spot: Control can be carried out by selecting disease-resistant varieties; practicing crop rotation; deep autumn plowing; cleaning the field; and increasing the application of phosphorus and potassium fertilizers.
6.3 Control of sunflower moth: When the sunflower moth adults are at peak emergence, use 90 Trichogramma cards per hectare, distributed evenly in the field in two batches at 3d intervals; when releasing, fasten the cards to the back of leaves with paper clips. During the larval stage (early August), spray 500~1000 times dilution of 90% trichlorfon wettable powder twice per hectare, with a control effect of over 90%.
6.4 Control of weeds and sunflower broomrape: After sunflower is parasitized by broomrape, it grows slowly, the plant becomes smaller, the flower head does not grow large, and the seeds are empty and shriveled, thereby reducing yield and quality. There are the following methods to control broomrape:
6.4.1 Carry out good quarantine of sunflower seeds; sunflower seeds must not be propagated or shipped out from plots where broomrape has grown.
6.4.2 Rotation control: Sunflowers must not be planted for 10 years on plots where broomrape has parasitized.
6.4.3 Manual weeding: When sunflowers are flowering, it is exactly when broomrape emerges in large numbers, so manual weeding should be carried out 1~2 times to remove broomrape seedlings.
Harvest
Harvest can begin when the sunflower maturity rate reaches above 90%. After harvest, dry promptly, and ensure it does not come into contact with diseased or toxic substances, ensuring product quality and hygiene.