SUNFLOWERS – a golden opportunity

January 2020

Jenny Mathews, Pula Imvula contributor. Send an email to jenjonmat@gmail.com

The beautiful golden sunflowers which paint parts of the south african countryside with brilliant golden yellow during the summer months, present a golden opportunity for farmers who include them in their production plans. This broad-leafed plant is versatile and profitable.

The main value of the sunflower lies in its high oil content. The seeds are compressed to extract oil and the by product is a valuable oil cake which is high in protein and oil and is mixed into cattle feed. Many poultry feeds and bird seed mixes also include sunflower seeds. Sunflower seeds are increasingly used as a health food, as a snack or a sprinkle in salads.

A warm and dry climate is considered optimal for sunflower production so sunflower has become a very important crop in the drier central and western regions of the country. Cool and moist conditions during the crop ripening phase are unsuitable, since rust and head rot can occur; while extremely hot conditions can cause charcoal rot. It has a shorter growing season and a greater tolerance of cold and even frost conditions than many other crops. It is a very adaptable plant. It can be planted late into summer – as late as the first week into February if rains come late, which has been the case in the past few years. 

Another advantage of growing sunflowers is the production costs of sunflowers are significantly lower as the plants are excellent at utilising residual nutrients in the soils left from previous crops. This is because the sunflower has a deep tap root which can dig deep for moisture and nutrients that have leached down and out of reach of many other crops. For this reason, the sunflower plant is an ideal crop to use in a crop rotation system with other crops like maize and beans or other leguminous crops. 

SUNFLOWERS ARE THE PERFECT DANCE PARTNER FOR MAIZE
Growing sunflowers after maize helps mitigate many of the problems triggered in a field. Some of the benefits of integrating sunflower into your crop rotation are:

Minimal moisture is required
The sunflower taproot system can reach as far as 1 m to 1,5m deep into the soil. This means they are better equipped than many other crops to handle drought conditions and they can deliver high yield production on limited moisture. A crop such as maize does not have the same root system and cannot access nutrient and moisture to the same depth as a sunflower can.

Helps break the disease cycle
What has become known as ‘the rotation effect’ is what happens when changing the crop grown in a field results in reduced disease transmission and pest resistance. When you change the crop, the disease pathogens die, and their life cycle is interrupted. An example is sunflowers should not be planted in the same field more than once every three to four years because sunflowers have a high susceptibility to Sclerotinia head rot and the same goes for soybeans which are susceptible to cyst nematodes. Crop rotation reduces weed build up too.  

RISKS ATTACHED TO GROWING SUNFLOWER 

• Sunflowers need a very good stand (plant population) in order to produce good yields of between 1,5 t/ha to 2 t/ha in the western summer cropping regions. Great care has to be taken to ensure the crop emerges successfully. My family of farmers hover over their new sunflower fields like a mother hovers over her newborn babies!
• Sunflowers do not enjoy extreme heat when emerging. The seeds do not produce a strong vigorous seedling at first. Even the slightest crusting of the surface soil can inhibit emergence, especially if heavy rains fall after planting and before emergence. If crusting occurs great care needs to be taken to till the soil and loosen the crust without harming the seedlings. 
• Because the sunflower has such a long taproot, it is necessary to be aware that while the crop can effectively utilise every drop of available moisture (which is a good thing), it can also tend to dry out the soil profile. This needs to be kept in mind when planning the follow-on crop in that field. 
• The efficient uptake of water by sunflower plants means that if late autumn rains do fall, it is particularly important to keep those fields weed free throughout the winter months so as to conserve as much late moisture as possible to counteract the drying effect of a sunflower crop.

SOME FINAL POINTERS 

• Sunflowers should not be planted in the same field more than once every 3 to 4 years.
• A sunflower crop does not leave much residue on the field after harvest – something to remember when one is trying to control soil erosion.
• Sunflowers thrive in well drained soils but will tolerate clay loam to sandy loam soils.
• One of the big advantages of the sunflower plant is, it is a vigorous grower and the plants and leaves are strong and robust in size. This means it competes well with most weeds, but it is important to control weeds early on, so they do not get a head start on the sunflowers.

Publication: January 2020

Section: Pula/Imvula