Key Management Techniques for Summer-Sown Oil Sunflower in the Mid-to-Late Growth Stage

After summer-sown oil sunflower enters the mid-growth stage, the main focus should be on management during the bud stage, flowering stage, and seed-filling stage. The specific management techniques are as follows:

I. Bud Stage Management

1. Intertillage and fertilization, ditching and earthing up: Carry out the third intertillage around the bud emergence period. Along with intertillage, apply 8 kg of urea per mu as a top dressing. The fertilization depth should be 8-10 cm, and root earthing up should be done together with intertillage.

2. Irrigate in drought, drain in waterlogging: Summer rainfall is abundant, so irrigation is generally not needed before bud emergence. If rainfall is excessive, pay attention to drainage; there should be no standing water on the ground. In drought years, irrigation should be carried out.

II. Management from Flowering to Seed-Filling Stage

1. Timely irrigation: In our area, autumn drought often occurs after the Beginning of Autumn, which is extremely unfavorable for yield formation. During the flowering stage, an adequate water supply must be ensured. If drought occurs, irrigate appropriately. Generally, the last full irrigation should be applied within 15 days after the end of flowering.

2. Foliar fertilization: Before flowering, spray the leaves with a 0.3% boron fertilizer solution plus a 0.2% potassium dihydrogen phosphate solution. Use two sprayer tanks of water per mu (30 kg), spraying once every 10 days for 2-3 consecutive sprays.

3. Pest and disease control: The main diseases include sclerotinia rot, downy mildew, and leaf spot, as well as verticillium wilt, gray mold, black spot, powdery mildew, and rust. The main insect pests include cotton bollworm and stem borers, as well as soil-dwelling insects and thrips.

4. Removing branches and artificial pollination: Some sunflower varieties have a branching habit, which affects the development of the main stem flower head. Therefore, when branches appear on the plant, they should be removed promptly. Sunflowers mainly rely on bees for pollination. For bee pollination, one hive is needed for 5-7 mu of land. In areas lacking bee sources, artificial supplementary pollination is needed to increase the seed-setting rate. Artificial pollination can be carried out at around 9-11 a.m. At this time, there are many pollen grains with strong vitality, and the pollination effect is good. The method of artificial pollination is: during the full flowering stage, gently rub two flower heads together, or use a clean towel with a 5-10 cm diameter cardboard inserted inside to make a round powder puff and gently wipe it over each flower head. Do this once every other day, and the yield increase is very significant. Seed-setting rate 85%.

III. Timely Harvest

The harvest period is in mid-to-late September. When the upper 4-5 leaves of the plant, the upper part of the stem, and the back of the flower head turn yellow, and the seeds become hard, it is ready for harvest. Li Jinzhong