Sunflower Close-Planting Methods: Seed Selection Tips and the Best Sowing Time

Sunflower is also called kuihua; its seeds 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 close-plant sunflowers? How do you select 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 above 98%, cleanliness greater than 98%, germination rate above 90%, and moisture content no higher than 15%.

3. Seed selection and cleaning: 4~5 days before sowing, select and 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, take them out and dry them, then pile them in a place at 15~20°C for one day and one night; when part of the seed coat has 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 preceding crops for sunflowers. In production, the crop rotation period is generally 5~7 years. Absolutely avoid continuous cropping or alternating cropping with the same crop.

3. Land preparation

3.1 Autumn plowing and ridging: the active soil layer should preferably be 25~30 cm, with plowing preferably 20~25 cm deep and deep loosening 30~40 cm. Achieve no missed plowing and no clods, promptly apply farmyard manure or green manure while ridging, and press the soil promptly after plowing.

3.2 Autumn plowing with spring ridging: on the basis of autumn plowing, when the soil thaws 14 cm in early spring, promptly harrow and level, ridge and press, and strictly prevent soil moisture loss.

3.3 Deep loosening and ridging: first loosen the original furrow, then break the original ridge platform to form new ridges, and press promptly.

3.4 Rotary tillage and ridging: suitable for soybean, potato, corn, and millet/broomcorn millet stubble. In early spring when the soil has thawed more than 14 cm, carry out rotary tillage and then ridge, and press 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 a sufficient amount of approved green manure.

3. Chemical fertilizer

3.1 Nitrogen fertilizer: during the sunflower bud stage, apply 100~150 kg of urea per hectare as a top dressing, prohibit the use of nitrate nitrogen, and the last top dressing must be carried out 30 d before harvest.

3.2 Phosphate fertilizer: apply 60~75 kg of phosphorus pentoxide per hectare, applied as base fertilizer or seed fertilizer combined with land preparation.

3.3 Potassium fertilizer: apply 35~50 kg of potassium oxide per hectare, applied as base fertilizer or seed fertilizer combined with land preparation.

Timely Sowing

1. Sowing period: sowing can begin when the temperature of the 5 cm soil layer is stable at 8~10°C for 3~5 consecutive d. In our area, it is generally May 15~May 20.

2. Sowing method: carry out manual spot sowing on the ridge, or open furrows with a plow and then sow manually. 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 spot (hole) sowing on ridges

4. Sowing depth: sowing depth 6~7 cm, achieve consistent depth, uniform soil covering, and 4~5 cm after pressing.

5. Sowing density: ridge spacing 65 cm, plant two ridges and leave one ridge empty, plant spacing 50 cm.

6. Sowing rate

6.1 Manual spot sowing: sow 3~4 seeds per hole.

6.2 Mechanical sowing: sowing rate 12.5~15 kg per hectare.

Field Management

1. Thinning: immediately thin the seedlings when one pair of true leaves appears, and finalize the seedlings when two pairs of true leaves have grown, leaving one strong seedling per hole.

2. Intertillage and weeding: three hoeings and three ridgings must be carried out. The first intertillage should be early, and can be carried out when the seedlings have two pairs of true leaves; where conditions permit, deep loosening in the furrow should be carried out. After the first hoeing and ridging is completed, hoe and ridge once about every 10 d and promptly remove large weeds.

3. Irrigation: irrigate timely and appropriately according to crop growth, especially during the bud stage and flowering stage, irrigate promptly in case of drought.

4. Removal of branches: 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, and after the morning dew has dried, gently tap the flower heads in turn. Bees can also be used for supplementary pollination, with 15 bee colonies placed per hectare.

6. Control of diseases, insect pests, and weeds

6.1 Control of sclerotinia: adopt a rotation of more than 5 years, combined with chemical control. Use 0.5% of the seed amount of quintozene or 0.5% of the seed amount of dimethachlon for seed dressing.

6.2 Control of brown spot: adopt measures such as selecting disease-resistant varieties, carrying out rotation, deep autumn plowing, cleaning the field, and increasing phosphorus and potassium fertilizer application for control.

6.3 Control of sunflower moth: during the peak adult emergence period of the sunflower moth, use 90 trichogramma cards per hectare, distribute them evenly in the field in two stages at 3 d intervals, and when releasing bees, pin the bee cards to the back of the leaves with paper clips. During the larval stage (early August), spray 90% trichlorfon wettable powder at 500~1000 times dilution twice per hectare, with an effectiveness above 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 for controlling broomrape:

6.4.1 Do a good job of sunflower seed quarantine; sunflower seeds are not allowed to be propagated or shipped out from plots where broomrape has grown.

6.4.2 Rotation control: sunflowers are not allowed to be planted for 10 years on plots where broomrape has parasitized.

6.4.3 Manual weeding: when sunflowers bloom, 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 be carried out when the sunflower maturity rate reaches above 90%. After harvest, dry them promptly, and ensure they do not come into contact with diseased or toxic substances, so as to ensure product quality and hygiene.