Sunflower has modest fertility needs, but does respond to nitrogen. When following soybeans in the rotation, roughly 50 to 70 lbs. N/acre is appropriate. Following a non-legume, about 80 to 100 lbs. N/acre is suitable. Animal manure or a legume cover crop can reduce or eliminate need for N fertilizer. One option is to spring plant a legume cover, such as Austrian winter peas in early April, let the legume grow for 2 months, then incorporate the legume and plant the sunflower in early June. This approach can eliminate the need for N fertilizer if good legume growth occurs. For sunflower planted double crop after wheat, apply about 60 lbs. N/acre if the wheat stubble is tillage incorporated, or about 80 lbs. N/acre if the sunflower is grown no-till in the residue. P and K should be applied based on soil test recommendation; for double cropping, extra P and K for the sunflower can be applied to the wheat the previous fall. On sandy soils, sunflower is often responsive to extra potassium fertilizer. Sunflower appears tolerant of soils with a pH down to 5.5, but consider liming if the pH is below 6.0, to improve nutrient availability in the soil. Starter fertilizer for sunflower will usually be beneficial only in cool soils of early spring, and should not be placed in direct contact with the seed.
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