Key points for growing sunflower crops in the UK
- The major climatic restraints on sunflower production in the UK are heat-related – the UK is on the edge of the climatically suitable zone for current sunflower varieties. For optimal growth and good establishment, an annual accumulation of 1400 day degrees above a base temperature of 6oC, and a soil temperature ≥7 oC (at 10cm) at drilling are key. These temperature sensitivities of the crop mean only certain regions of the UK are suitable for growing the crop.
- Sunflowers are a spring grown crop which provides rotational advantages such as: a break in a run of cereal crops and opportunities to implement weed control using non-selective herbicides
- Ideally sunflowers should be grown following cereals or fallow rather than after crops that can increase risk of stem and head rot (Sclerotinia sclerotiorum) such as potatoes or oilseed rape.
- The best soil type is well-drained loam that warms up quickly in spring. Sunflowers can grow on nearly any soil type, but low pH soils should be avoided.
- Sunflowers volunteer in subsequent crops for ≥1 years which can provide a weed problem in following crops such as potatoes and peas.
- Compaction should be avoided, and the growing site should be ploughed and sub-soiled if there is a compaction risk.
- In terms of nutrients, sunflowers have a low fertiliser nitrogen requirement (25 and 50 kg ha-1 is sufficient), quite high soil potassium and phosphate requirements (40-60 kg ha-1 is a normal maintenance application) and a high sensitivity to boron deficiency. Thus agrochemical inputs are generally quite low but use of boron supplementation may be sometimes be essential.
- Harvest ideally occurs during September.
- A 30% seed moisture (when back of the seed head is yellow and bracts have started browning) will provide the best oil quality.
Weed, pest and disease control
- Annual broad-leaved weeds (e.g fat hen) are generally the most threatening weeds as they tend to germinate after drilling but can grow vigorously and outcompete the crop. Annual grass weeds can also be present at significant levels in sunflower, and cereal volunteers can present problems.
- The few herbicides approved for use in sunflower include trifluralin and pendimethalin (non-selective herbicides used prior to drilling) and sethoxydim (the latter was the only post-emergence chemical approved at the time).
- Sunflower hosts a number of pathogens which can cause crop damage. These include fungal pathogens such as Sclerotinia wilt and rot (Sclerotinia sclerotiorum) and Botrytis head rot (Botrytis cinerea), bacterial pathogens such as bacterial soft rots (Erwinia carotoovra; Pseudomonas spp.) and viral pathogens such as sunflower mosaic and tobacco streak.
- It is believed S. sclerotiorum and B. cinerea are the most threatening to UK yields
- Some of the main methods for reducing diseases include: using resistant or tolerant crop varieties (searching for resistance to S. sclerotiorum has been the major focus of sunflower breeding programs) and cultural control (cultivation practices, seed hygiene, row spacing)
- At the time of this report no fungicides have been cleared for use on crops and it is believed these are not an economically realistic control method.
- Currently UK sunflower crops are relatively free of pest problems but Aphid damage poses the biggest threat as cropping area expands and pest pressure is likely to increase.
- At the farm level sunflower crops appear more profitable than other spring sown break crops.
- At Boxworth (where this study was undertaken), it was found that the gross margin of sunflower was £52/ha higher than comparable spring crops.
- However, compared to oilseed rape, sunflowers are £130/ha lower in profitability.
- In 1998 UK yields were 2.1t/ha.
Conclusions and recommendations
This review highlighted that whilst sunflower can be a viable UK crop, it requires very specific growth conditions and there is significant risk associated with growing it. This appears to have prevented wider uptake by UK farmers. Recommendations for future research and development included:
- Crop establishment: good establishment is key for determining yield and profitability. Research should focus on overcoming the current problems (e.g strict soil conditions, moisture availability, sowing depths, pests and diseases) encountered during this phase.
- Post-Emergence development: there is little information on basic physiology of sunflower production in UK. Improved understanding of factors such as crop nutrition and environmental interactions will permit greater yield outputs via effective husbandry manipulation.
- Quality appraisal: need to investigate factors affecting fatty acid composition of seed grown in the UK to produce the best quality oil.
- Harvest technology: improve the timing and mechanics of harvesting, and efficiency of drying and storing seeds.
- Heat use efficiency: UK sunflower crops have lower heat use efficiency than those grown on the continent. Information from studies (see point 2) could help explain these differences.
- Crop monitoring: As cropping area of sunflower increases pest and disease occurrences may increase. It is important to monitor this.
- Technology transfer: Link up farmers, breeders, merchants and end users. Reviews such as this and promotional campaigns can help make growers aware of the benefits of growing sunflowers as a spring break crop.
To find out more about market information and how sunflower production has changed in the UK since this report was written, you can use resources such as the Food and Agriculture Organization of the United Nations statistics tool (FAOSTAT), Statista, and The Observatory of Economic Complexity (OEC) online tools. You can also find updated authorised plant protection products for sunflowers on the Health and Safety Executive Pesticides register.