How to protect sunflower yields from heat stress and drought

Sunflower farming faces growing challenges from drought, heat, and other environmental stresses. Pannar agronomists support farmers by combining in-depth research, field trials, and expert advice to optimise hybrid selection and planting times.

Farming today demands more than just good seeds; it requires smart strategies to tackle challenges like drought, heat, and low humidity. Corné van der Westhuizen, a product agronomist with Pannar Seed’s Western production region, brings 20 years of expertise to help farmers understand how abiotic stress affects sunflowers.

Drawing on his experience working with farmers, sales teams, and product demonstrations, Van der Westhuizen underscores the importance of hybrid selection and optimal planting times. These decisions, he explains, are crucial to maintaining yield and oil quality, empowering farmers to succeed under increasingly variable climate conditions.

To understand why these management decisions matter, it’s important first to grasp what abiotic stress is and how it impacts sunflowers.

What is abiotic stress, and how does it affect sunflowers?

Van der Westhuizen, who holds a BSc Agric. and honours from the University of the Free State, defines abiotic stress as non-living environmental factors or the combination of environmental factors like drought, heat and low humidity.

These types of stress disrupt sunflower morphology (structure) and physiology (processes) – reducing cell division, leaf area index, and photosynthesis – which ultimately leads to lower grain yield and oil content.

“Sunflower (Helianthus annuus L.) plays a crucial role in South African agriculture due to its adaptability to a wide range of climatic, soil, and management conditions. It is valued for its high oil and protein content, making sunflower an essential source of both food and industrial oil.

“Sunflowers’ deep-rooted growth habit allows them to tolerate moderate drought, which is particularly important in regions prone to seasonal drought. This resilience makes sunflowers a reliable crop for farmers seeking stability in yield and quality, even under challenging environmental conditions,” he explains.

The primary abiotic stresses impacting sunflowers are the combination of drought, heat and low humidity, especially during sensitive developmental stages such as flowering and grain-filling.

These stresses, Van der Westhuizen adds, can disrupt plant processes, affecting nutrient uptake and availability, photosynthesis, and ultimately components that determine yield and quality.

“Sunflowers are moderately drought-tolerant, but prolonged or severe drought and high temperatures can significantly reduce their productivity and oil quality.”

Managing heat stress and drought

He says drought and heat stress lower the plant’s relative water content (RWC), causing stomata closure that reduces CO₂ uptake and transpiration. This leads to chlorophyll degradation, resulting in pale leaves and diminished photosynthetic efficiency.

The reduction in leaf area index (LAI) further limits the plant’s capacity to photosynthesise, which is essential for production and growth. These disruptions collectively result in reduced grain yield, lower grain weight, and fewer grains per head.

Effective management practices include careful hybrid selection and optimal planting date determination. These strategies help manage the Genotype x Environment x Management (GxExM) interaction and can potentially reduce the crop’s exposure to stress during sensitive developmental stages.

By selecting locally tested and adapted hybrids and timing planting to avoid peak stress periods, farmers can improve yield, yield stability and oil quality even under challenging environmental conditions.