The yield and processing quality of sunflower seed as affected by the amount and timing of nitrogen fertiliser

Abstract

The response of sunflower (Helianthus annuus L.) seed yield and seed processing quality to the amount and timing of nitrogen were studied in a field trial. Nitrogen application rates were 20, 70 and 120 kg ha⁻¹ with limestone ammonium nitrate as the nitrogen source. Timing of application treatments were all nitrogen applied at planting and split in ratios of 1:1 and 1:3, applied at planting and at the beginning of flowering. Timing of nitrogen application had no effect on seed yield or any of the seed quality characteristics. Seed yield increased on average by 22% per 50 kg of nitrogen applied per ha. Hullability was not affected, while seed oil content declined and the seed protein content increased moderately with increased amounts of nitrogen, leading to a decline in the amount of recoverable oil, an increase in the potential oil cake yield, an increase in the protein and decrease of the crude fibre content of the expected oil cake. The changes in seed quality characteristics were equal or less than 10% per 50 kg of nitrogen applied per ha.