How To Improve The Oil Yield Of A Sunflower Crop

Dr Safiah Ma’Ali, a senior researcher at the Agricultural Research Council’s Grain Crops Institute, outlines a recent South Africa study demonstrating that farmers can significantly improve sunflower oil content and yield by adjusting planting dates.

- Dr Safiah Ma’Ali

Annual global production of sunflower oil is about 18 million tons. As it utilises soil nutrients efficiently due to its deep roots, the crop is usually grown in dryland systems. South Africa’s sunflower seed production was 862 000t in 2018, according to the Crop Estimates Committee.

Sunflower is produced mostly for its oil. Oil concentration, expressed as a percentage of seed dry mass, generally determines the industrial yield of the crop. In some countries, each percentage point that oil content increases between 40% and 45% earns a 2% price premium; in contrast, buyers demand a 2% price discount for each percentage point decrease in oil content between 40% and 38%, and a larger penalty as oil percentage decreases further. Both seed yield and oil percentage are thus important for maximising gross income.

When sunflowers have access to optimal water and nutrient requirements, temperature and exposure to sunlight play key roles in determining yield components and grain quality. Grain oil concentration is determined mainly by the amount of photosynthetically active radiation (the solar radiation that plants can use in photosynthesis) intercepted per plant during the grain-filling period. The optimal planting date is crucial, as it ensures good seed germination as well as the timely appearance of seedlings and good root development.

The effects of environmental factors on oil content vary according to the crop growth stages, as oil yield components and grain quality are defined in different phenological stages. Seedling emergence is a sensitive stage; abiotic stresses, such as high soil temperature (above 40°C), can cause delayed emergence, resulting in poor yield.

STUDY