Abstract:

Sunflower is an important oilseed crop in Uganda, with expanding areas under production. The crop is a heavy feeder, extracting large amounts of nitrogen (N), phosphorous (P) and potassium (K) from the soils. These nutrients contribute significantly to the amounts and quality of sunflower oil which gives the crop its paramount importance, besides the residual cake after oil extraction. This extraction of soil nutrients has led to unconfirmed, discouraging allegations from some circles, that sunflower depletes soils. Of course any crop produced continually, without following proper rotation guidelines, not only depletes the soils, but also aggravates pest problems. Proper soil management practices need to be followed and additional fertility and amendments need to be added to the soils. Adequate soil fertility is one of the requirements for profitable sunflower production. Nitrogen (N) is the most yield-limiting nutrient, unless there are high residual NO3-N levels in the soil. Phosphorus (P) is the next most limiting nutrient.