Detailed Explanation of Key Technical Points for Scientific Fertilization of Sunflowers
Based on the symptoms, it may be stem rot, a form of sclerotinia disease, which can be controlled with thiophanate-methyl. Or use thiophanate-methyl combined with carbendazim, procymidone, and dimethachlon for control.
1. Base fertilizerTypes. Mainly organic fertilizer combined with chemical fertilizer.
Application period and method. Apply base fertilizer in combination with autumn plowing; this is more conducive to preserving fertilizer nutrients than applying it during spring plowing and can improve the emergence rate. Application method: in combination with mechanical operations, use broadcast application, harrow evenly, and then plow. For horse-drawn implement operations, apply the fertilizer in the furrows and then close the ridges.
Fertilizer amounts. Organic fertilizer 1000-2000 kg per mu; chemical fertilizer: nitrogen 5-8 kg, phosphorus pentoxide (P2O5) 4-5 kg. Potassium fertilizer can be determined according to the soil potassium content obtained from soil testing; if it reaches the normal standard, potassium may not be applied, and if it does not reach the normal standard, potassium sulfate can be applied at 3-4 kg per mu.
2. Seed fertilizer.
Seed fertilizer should be mainly phosphorus to achieve the goal of strong seedlings. For example, ammonium bicarbonate or ordinary superphosphate plus a small amount of urea can also be used as seed fertilizer.
Method of using seed fertilizer. In combination with sowing, apply organic fertilizer and chemical fertilizer 2-3 cm below the seeds, or 2-3 cm beside the seeds.
3. Topdressing.
Fertilizer applied after sunflower emergence is called topdressing. Sunflower is a crop with a relatively high fertilizer requirement. Relying only on base fertilizer and seed fertilizer cannot fully satisfy the nutrient needs of sunflowers during budding, flowering, and the later growth period, when vegetative growth and reproductive growth proceed simultaneously. Especially for summer-sown sunflowers, topdressing is even more important when base fertilizer is insufficient or not applied. Topdressing is mainly nitrogen fertilizer, combined with a certain amount of potassium fertilizer. Fertilizer types include ammonium nitrate, urea, ammonium bicarbonate, potassium chloride, and other chemical fertilizers, as well as quick-acting fertilizers such as decomposed human excrement and urine and plant ash. In addition, it also includes some trace elements such as zinc, molybdenum, manganese, and copper. The amount and timing of sunflower topdressing are determined mainly based on fertilizer requirements at different growth stages, soil fertilizer supply capacity, climate conditions, and the amounts of base fertilizer and seed fertilizer applied, and in production it is often also combined with field management measures. The period from budding to flowering in sunflowers is precisely a vigorous production stage in which vegetative growth and reproductive growth occur simultaneously, requiring large and concentrated nutrients, so topdressing should be arranged before this period. Generally, nitrogen fertilizer and potassium fertilizer have a better effect when applied at the 7-8 leaf stage. Generally, small holes are dug 10-15 cm from the base of the sunflower root and stem to apply fertilizer, and then soil is immediately covered. The fertilization depth depends on the type of topdressing and soil moisture conditions. Fertilizers that volatilize easily, such as ammonium bicarbonate and ammonia water, should be applied deeply, and in cases of drought and dry soil they should also be applied deeply so that the fertilizer contacts moist soil and can readily take effect in time. If using intertillage and early topdressing, it can be combined with the first intertillage, with a cultivation depth of 8-10 cm, and it must be about 15 cm away from the seedlings. For late topdressing, it can be combined with the last intertillage, and the fertilizer can be applied between rows, with the cultivation depth still 8-10 cm. In short, when topdressing, attention should be paid to the depth and applying it into the moist soil layer, but the plant root system should not be damaged because of deep application, and attention should also be paid to keeping the fertilizer from being too close to the plants and burning the roots.
4. Foliar spraying.
Spraying 0.005% zinc, copper, manganese, and molybdenum solution at the sunflower budding stage can increase the oil content of the seeds, reduce the empty and shriveled seed rate, and improve seed plumpness. Foliar spraying with 0.1% urea solution has a clear yield-increasing effect. Spraying a 1:3:3 nitrogen, phosphorus, and potassium solution at sunflower flowering can greatly increase yield and can also increase oil content.