Sunflowers - a growers guide - Dr Sarah Cook, ADAS UK Ltd, ADAS Boxworth, Boxworth, Cambs CB23 4NN - Defra, UK
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Sunflowers
- a growers guide
Dr Sarah Cook, ADAS UK Ltd, ADAS Boxworth, Boxworth, Cambs CB23 4NN.
Sarah.Cook@adas.co.uk
WWW.ADAS.CO.UK WWW.GBSEEDS.CO.UK WWW.HGCA.COM
WWW.WARWICK.AC.UK/GO/CLIMATECHANGE/INNOVATION-
NETWORK
January 2009
1INTRODUCTION
This current guide was funded through the Defra Innovation Network, led by the
University of Warwick (www.warwick.ac.uk/go/climatechange/innovation-network),
G B seeds Ltd and HGCA.
THE MARKETING AND ECONOMICS
450.0
Seed oil and meal from oilseed crops
400.0 are major world commodities, the
350.0
major crops being soya, rapeseed,
million tonnes
300.0
250.0 palm and sunflower. Globally soya is
200.0
150.0
the largest oilseed crop area,
100.0 dominating both the oil and meal
50.0
markets. Soya meal is valuable as a
0.0
2004/05 2005/06 2006/07 2007/08 protein source for animal feeds and
Soya Rapeseed Cotton Peanut Sunflower Palm Copra this means soya meal and oil supply
affects the price of all oilseeds.
World sunflower production
The major producers of sunflower
8
are the EU, Argentina, Russia and 7
Ukraine. The soft black-seeded 6
million tonnes
5
sunflowers are the ones favoured by 4
3
the UK pet-food market. 2
The UK produces up to 3,000 tonnes 1
0
of sunflower seed each year and is a
na
a
a
e
u
n
a
A
di
le
da
in
i
in
US
ss
net importer of seed, oil and meal. No
i
In
Ch
ra
nt
ta
Su
Ru
ge
Uk
To
Ar
crushing of sunflower is currently
done in the UK.
2Economics
Seed is the most expensive input and it may be possible to reduce this cost once the
crop is more widespread and more suitable varieties become available. There is no scope
for home-saved seed as the crop is a hybrid. Fertiliser costs are low.
Sunflowers yield between 1.5-2.5 t/ha in the UK, but this is dependant on the season.
Yields in 2007 and 2008 were lower than average due to wet conditions during ripening
and harvest. Current prices (2009) are approximately £300-350/t. Markets tend to be
local, a good example being Vine House farm foods (www.vinehousefarmfoods.co.uk).
Here 100 ha of sunflower are grown to provide seed for bird food products sold direct
from the farm.
Until recently sunflowers were grown by ADAS at Boxworth in Cambridgeshire. Yields
ranged between 1.5-2.6 t/ha. At this site grass weeds, especially black-grass are a
problem and sunflowers provided an opportunity for a stale seedbed prior to drilling.
The wildlife benefits of the crop were many and a flock of up to 300 greenfinch was
seen around the crop. Harvest was generally in early October but this was not a problem
for the entry of winter wheat. After several successful years, restructuring the
farming operation meant a return to a predominantly winter cropping rotation.
CROP PLANNING
Varieties
A range of sunflower varieties have been trialed in the UK by the UK Sunflower
Association, limited variety testing is still done by NIAB. Sanluca (Syngenta seeds) and
Antonil (Pioneer Hi-bred) are the most commonly grown varieties suited to the UK
climate.
Crop rotation
Growing sunflowers in the rotation offers:
• An overwinter fallow period which allows control of grass
and broad-leaved weeds through the use of non-selective
herbicides.
• An effective take-all break providing grass weed control
is good.
However rotation planning should take account of:
• Susceptibility to Sclerotinia which may pose threats to high value crops in the
rotation such as potatoes and others.
• Avoid sowing sunflowers after crops that leave a large nitrogen residue e.g. Kale,
sugar beet or grassland.
• Short rotations of four years or less which increase the risk of Sclerotinia to
any oilseed crops
3Soils and cultivation
Sunflower can be grown on a wide range of soil types. However, a
well-drained soil that will warm up rapidly in spring is preferred.
The drought-tolerance of sunflowers also makes it suitable for
use on more drought-prone soil types.
The optimal pH range is from 6.0 to 7.5.
Seedbed preparation is crucial for sunflowers and a fine firm seedbed, similar to that
for sugar beet and peas should be prepared.
SOWING
Seed treatment
Seed is imported and is pre-dressed. Consult your supplier for further information.
Drilling date
The soil temperature in the top 10 cm of soil at drilling should be at least 6-8°C. If the
soil is too cold then germination will be patchy and delayed making the crop vulnerable
to a greater degree of pest damage. Drilling usually occurs from mid-April onwards in
southern and eastern England.
Seed rate
Plant population is an important factor in the production of a sunflower crop since it can
affect a variety of yield components.
Low populations result in plants with large heads, these tend to
ripen slowly.
An established plant population of between 80,000 and 110,000
plants/ha with a row width of 34 cm is optimal. Actual sowing
rates should be between 10% and 20% higher than the target
plant population to allow for losses during establishment. The lower figure applies to
later sowings, light soils, warm seedbeds and conditions generally favourable to
germination; the higher to heavy clay soils under less favourable conditions.
Due to the nature of the sunflower crop there are no opportunities for reductions in
seed rate.
Drilling
Seed should be sown to a depth of from 2.5 to 5.0 cm (1 to 2 inches), according to seed
size and soil type and condition. In dry conditions, seed should be sown more deeply
into moisture.
4Most seed-drills can be adapted for use with sunflower but
seed rate, seed spacing and row width are critical.
Sunflower is a non-branching crop and cannot compensate for
uneven plant-spacing and low plant populations. Accuracy of
drilling has an important bearing on yield and quality.
Pneumatic disk drills, belt drills and pneumatic cereal drills
have all been used to establish successful sunflower crops. Near optimal seed spacing
can be achieved with the precision drills. With a pneumatic cereal drill optimal row
spacing can be achieved blocking-off alternate coulters, but these drills are not well
adapted to the low populations required by the crop. Plant spacing within the rows can
be very uneven,
Drill calibration.
For drills of all types, accurate calibration is essential, both to
achieve the optimal plant population and to conserve expensive
seed. Grower experience has shown that best results are
achieved by calibrating the drill over a full hectare. Unless the
drill has a press-wheel behind the seeder unit, the seedbed
should be consolidated immediately after drilling, using a Cambridge roller. This not
only conserves moisture and improves seed-soil contact but also increases the
effectiveness of subsequent herbicide applications.
CLIMATE CONSTRAINTS
There are two major constraints on sunflower production, both heat-related, firstly soil
temperature at sowing, which determines the earliest practicable sowing date and
secondly the amount of heat available for use by the crop during the available growing
season.
Soil temperature
The soil temperature at drilling should be 6-8°C in the top 10 cm of soil. A map of soil
temperatures at 30cm depth in May (Fig 3) shows where temperatures are >10°C, these
areas are suitable for sunflower establishment.
Heat accumulation
The principal factor determining the rate of crop development is the accumulation of
heat, as influenced by mean daily air temperature above a base level of 6 °C, as for
maize. Areas that achieve 1400 day degrees are best suited to production (Fig 4.)
5Fig 3. Mean Soil temperatures on 1 May Fig 4. Average accumulated temperature
at 30cm (°C) (May-September >6°C)
Climate change and sunflowers
• Rising Global temperatures will make sunflowers a viable proposition on 50% of
the area of England by 2020 (Fig 3) and 79% by 2050 (Fig 4).
• Sunflowers will become a viable alternative break crop to winter oilseed rape and
grower choice will be made on commodity price. Winter oilseed rape may be
selected when there is adequate rainfall in the autumn for successful
establishment. When autumns are dry sunflowers can be drilled in the following
spring. This scenario is currently experienced in France.
• Drier springs will make it more difficult to establish traditional spring crops;
this would be favorable towards an increased area of sunflowers.
• The disease spectrum will change, botrytis incidence will decrease, but
sclerotinia, phoma, phomopsis and verticillium incidence and level will increase.
• Yields will increase, as yields of up to 5 t/ha have been achieved in France and
Germany.
• Sunflowers will be crushed in the UK as a separate commodity and the crop may
be subject to increased premiums from the crushers because of reduced
transport costs within Europe.
• The global production of sunflowers may remain stable but production will move
northwards to more climatically suited areas.
6Fig 1 Average Accumulated Temperatures Fig 2 Average Accumulated Temperatures
(April to September >6°C) 2020’s Scenario (April to September >6°C) 2050’s Scenario
CROP NUTRITION
Nitrogen
The deep-rooting nature of sunflower can remove nutrients from depth in the soil
profile. As a result the crop will yield satisfactorily at quite low levels of soil nitrogen
and nitrogen fertilizer applications may be unnecessary.
High levels of nitrogen can lead to excessive vegetative development, encouraging
disease, delaying maturity and reducing seed oil content.
UK experience indicates that applications of more than 25-50 kg/ha are rarely
required.
Phosphate and potash
Phosphate is required at relatively low levels by the crop. A maintenance application of
from 40 kg to 60 kg/ha is usual.
Sunflowers require a relatively high level of potassium but most of this is returned to
the soil after harvest. A maintenance application of from 40 kg to 60 kg/ha is usual,
often as part of a compound fertilizer with phosphate.
7Micronutrients
Sunflowers are sensitive to boron deficiency, and can be a particular problem on
calcareous or sandy soils where boron levels are often naturally low.
Boron is taken up chiefly during the vegetative period prior to heading and signs of
deficiency usually become apparent during flowering and seed maturation. A
characteristic feature is poor seed-set, with many heads having large areas of hollow
seeds. Other symptoms are red-brown necrotic patches and abnormal head and neck
development. The timing and rates of boron application are shown below.
Soil and climate factors Soil Boron level (ppm) Treatment
Non-calcareous pH7.5 0.5
300-500 g/ha as a foliar spray at GS 2.5-3.2
Sandy 0.5
Molybdenum, copper and manganese deficiencies can be problems in very acid soils (Irrigation
Sunflower is significantly more tolerant of dry conditions than other crops grown in the
UK. The most water sensitive stages are the establishment phase and the stages
between the unfolding of the ray florets to the completion of pollination. Drought
stress during these periods limits both yield and oil content.
In France, sunflower can produce reasonable yields where rainfall is as low as 420 mm
(17") per annum. Much depends on the seasonal distribution of the rainfall and soil
texture and structure. Sufficient seedbed moisture allows the roots to grow rapidly
into the lower soil levels, and survive by exploiting the water table. Water availability in
the UK is not usually limiting
Use of irrigation in the UK would be limited to the establishment phase, but there is
currently no information available to UK growers
PEST AND DISEASE
Pests
In the UK the crop is most vulnerable to slugs from drilling until one pair of true leaves
is visible. All soils are at risk but particularly cloddy or stony soils with high levels of
organic debris. Slug pellets should be applied to all crops at risk.
Pigeons are a major pest of UK sunflowers; they graze the crop as it emerges, snipping
off the growing point. Similar damage has been attributed to pheasants. Rabbits can
also cause damage by grazing emerging crops.
Finches can damage ripening crops, but they tend to venture only up to 24 m into the
crop, because of predators. In a small field (less than 4 ha), bird damage can be
considerable and the whole crop can be lost. To decrease damage to seed-heads, plant
spacing should be controlled to reduce head size and increase head angle to discourage
perching.
Other mammals, such as mice and badgers, can also damage crops during ripening, but
this is generally a localized problem.
Insects - There have been reports of minor damage caused by Tortrix larvae, leaf
minors and looper caterpillars, thrips and silver Y moths (Autographa gamma L.).
Various aphids, including Brachycaudus helichrysi, Aphis fabae and Myzus persicae have
been recorded but caused little damage; colonies of up to 1000 individuals have been
noted.
Currently no insecticides are approved for use in sunflowers.
Disease
Sunflower is host to a number of fungal, bacterial and viral pathogens that can cause
varying amounts of crop damage, the two most common being Botrytis cinerea and
Sclerotinia sclerotiorum
9Botrytis head rot
Botrytis head rot or grey mould is caused by Botrytis cinerea, a fungus widely spread
throughout a range of crops. It occurs frequently in sunflower growing under relatively
cool (15-25ºC) and wet conditions and may cause extensive damage.
Botrytis can develop on seedlings, stems and leaves, but only if the fungus gains entry
through wounds. However, it is most damaging when it
infects heads.
Botrytis makes its first appearance on the back of the head
as sunken brown spots. As the infection develops, the
lesions spread and eventually the back of the head becomes
soft and grey.
A late season infection on the head can result in increased
seed losses during harvest; earlier infections may reduce
both yield and quality.
There are no chemical options for controlling Botrytis in the
sunflower crop. Applying a desiccant when seed moisture is
about 30 per cent can aid ripening or advancing the harvest
date by up to seven days.
Mycotoxins are not an issue for sunflowers as the husks are removed before
consumption
Sclerotinia wilt and rot
Sclerotinia causes stem and head rot in sunflower
Stem rot is caused by fungal threads (mycelium) already in the
soil at the beginning of the season and leads to wilting and
finally the total collapse of the plant. Head rot is due to air-
borne spores infecting the plant during the growing season and
may result in the total destruction of the head and plant.
Sclerotinia is not restricted to sunflower but has a wide range of hosts,
of varying susceptibility (Table 1). The severity of attacks on susceptible
crops is related to the number of such crops
grown in the rotation. Increasing the interval
between susceptible crops reduces the risk of
infection. There is no chemical control available
in sunflowers.
10Table 1. Relative susceptibility of different crops to infection by S. sclerotiorum
Crop Degree of Crop Damage Production of sclerotia
Sunflowers **** *****
Phaseolus beans **** ****
Winter oilseed rape *** ***
Potatoes ** **
Spring field beans ** *
Spring oilseed rape ** *
Linseed ** *
Carrots ** ***
Peas * ****
GROWTH
Sunflowers are planted at the end of April and grow rapidly given warm conditions. Buds
begin to form in mid June and begin to show colour during the second week of July.
Flowering lasts for approximately 2 weeks and then the crop begins to senesce ready
for harvest in early October.
In the UK water availability is not limiting, but excess rainfall will tend to result in
taller crops.
Predictions of global warming would bring drilling and harvesting dates earlier. Currently
weather conditions in the UK mean successful crops 9 years out of 10 in southern
England.
April May June July August September October
1.0 1.1 2.1 - 2.n 3.1 3.5 4.1 4.3 5.0 5.1 5.2 5.3
Emergence Vegetative Bud Flowering Maturity
growth formation
11HARVESTING AND POST HARVEST
Moisture content at harvest
Harvest should take place when seed moisture content reaches 30% or less. Oil quality
does not suffer between 15-30% moisture content.
Appearance Moisture
content
(%)
Back of the head is lemon yellow, bud scales surrounding the disk 40-30
are brown mottled. Too early
The back of the head becomes deep yellow and the bud scales >20
brown. Approximately two thirds of the leaves from the base have
senesced. Early
Bud scales are totally brown and the back of the head is marbled 15-20
brown. All leaves have senesced and stems are drying out. Ideal
Harvesting
A conventional cereal combine can be used with little
modification, but if sunflowers are grown regularly then
harvesting trays can be fitted to the cutter bar. The reel
tines should also be covered to avoid impaling the flower
heads. Combine settings should be similar to those used for
harvesting beans and the crop should be harvested during
the day and when dry. Care should be taken to avoid overloading the returns auger.
Preferred combine settings are as follows:
Drum speed 400-600 rpm
Concave setting Wide open
Sieve size 10-12mm
Fan speed Adjusted to avoid losses over the back
Forward speed 5 to 6 mph (running speed)
Check manuals for specific details.
12To minimize the amount of admixture with the grain, only a small amount of the stem
should be cut. Some heads may fall forward, away from the combine table, when
harvesting. This can be reduced by a relatively fast forward speed.
The stubble can be chopped
by the combine or by using a
forager or heavy discs. The
field can then be ploughed
and drilled if the following
crop is a cereal. Volunteers
can be dealt with using a
broad-leaved herbicide, but they may continue to appear throughout the spring.
Grain quality
Seed destined for the birdseed market is usually sold at 9% moisture with a maximum
admixture content of 2%. UK companies do not commonly specify oil content.
DRYING AND STORAGE
Sunflower seed dries quickly but the seed should never be
stored wet. Sunflower seed will heat up if allowed to stand while
wet. Use of a drying floor is the safest method and the seed
should be at a maximum depth of 1 metre. The best method of
drying is to use cold air until the moisture content falls to 15 per
cent. The seed can then be cleaned and sufficient heat applied
(using the same temperature as for oilseed rape) to reduce the
moisture to 9 per cent for long term storage.
The seed should be left for seven days to allow the seed moisture to equalize before
drying again if necessary.
BEWARE
Sunflower seed has a lint-like coating that can easily be rubbed off to form a light oil
bearing dust. If this is taken into the unprotected intake of a continuous drier there is
a high risk of fire. Drying methods that include any form of agitation or movement of
the seed should, therefore, be used carefully. One technique that has proved
successful is to reduce the bulk of the moisture using a floor drier and then complete
the operation in a continuous drier.
FOLLOWING CROPS
Sunflowers were grown at ADAS Boxworth, Cambridgeshire for ten years, beginning in
1990. Over a five year period sunflowers were harvested on average 74 days after
oilseed rape and the following wheat crop was drilled within 25 days of harvest (see
Table 2).
13Table 2. Average dates of drilling and of harvest and yields of wheat following crops of
sunflower, winter beans and oilseed rape during the period 1992-1997.
Break-crop Average date of Average date of Days between Yield after break-
harvesting drilling wheat harvest and drilling crop as a % of
break-crop crop the following crop mean yield
Sunflower 7 October 27 October 20 102.0
Winter 18 August 8 October 51 103.3
beans
Winter 25 July 28 September 68 103.6
oilseed rape
Cultivations following sunflowers were usually non-inversion, such as discing. The stems
break up easily and cause no problems with seedbed preparation.
Sunflower as a weed
The seeds of sunflower can persist in the soil for up to
five years and have the ability to germinate at a
considerable depth and over a long period. At ADAS
Boxworth, on a clay soil susceptible to cracking,
sunflowers were found to germinate in the cracks and
appear in following crops. The growth of these
volunteers was more vigorous where the crop was less
competitive, especially on headlands and in gateways. In cereals metsulfuron-methyl,
tribenuron-methyl and thifensulfuron –methyl all provide control of volunteer sunflower.
Volunteer control in sugar beet with clopyralid provides some control at the 2 leaf stage
(G.S. 2.2). In peas, bentazone provides an effective means of control.
FURTHER INFORMATION
UK sunflowers
http://www.hgca.com/content.output/3308/3308/Crop%20Research/Crop%20Research/Sunflo
wers.mspx
National Sunflower Association (USA) http://www.sunflowernsa.com/
CETIOM (France) http://www.cetiom.fr/#
Written by Sarah Cook, ADAS UK
Ltd (sarah.cook@adas.co.uk ).
This document was funded through WWW.ADAS.CO.UK WWW.GBSEEDS.CO.UK WWW.HGCA.COM
the Defra Innovation Network, led by
the University of Warwick, G B
Seeds Ltd and HGCA.
WWW.WARWICK.AC.UK/GO/CLIMATECHANGE/INNOVATION-
January 2009
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