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Sunflower Production and Management

Sunflower Crop
     

Sunflowers In Manitoba

All sunflower varieties grown in Manitoba are hybrids and based on their end use, can be classified as either oil- or confection-type sunflowers.

Approximately 60% of all Canadian sunflowers are confection-type, which are marketed primarily as roasted snack food in the shell or as dehulled seeds for the baking industry. Although a significant percentage of this market is domestic (North America), Canadian processors are increasingly accessing markets in Europe, the Middle East and Asia.

Oilseed sunflowers are used in the birdfeed and crushing industry for sunflower oil, which is one of the highest quality vegetable oils.

The birdfood market primarily uses oilseed sunflowers, however some of the smaller confection seeds are also used for birdseed.

Oil-Type Sunflowers

Sunflowers grown for oil are characterized by black hulls. With oil-type sunflowers there are 3 different groupings: traditional, mid-oleic (NuSun), and high oleic. These groupings are based according to their specific oil profile. The mid-oleic varieties have an oil profile that is intermediate to the traditional and the high-oleic sunflower varieties.

Confection-Type Sunflowers

The non-oil or confection-type sunflowers have striped hulls and are used primarily for the human food market. Yields of confectionary sunflowers are closely tied to the quality of the seeds. Only the largest of the confection type sunflowers are used for human consumption and there is little tolerance for bird or insect damage. Confection-type sunflowers have a standard bushel weight of 25 lb/bushel as compared to 30 lb/bushel for oil- type sunflowers. Canadian Grain Commission minimum test weights for No. 1 Canada sunflowers are 155g/0.5L for confection-type sunflowers, 169g/0.5L for oil-type sunflowers.

Sunflower is a tall broad-leafed plant, usually with a single main stem and 1 head per plant. The stem is hairy and becomes very fibrous as the plant matures. Sunflowers are in full flower 70 to 80 days after planting and require about 120 days to mature. Sunflowers are a heliotropic species, which means that immature sunflowers in the bud stage will track the sun from east to west during the day and will return to face the east during the night. However, when the blooming stage is reached sunflowers are no longer heliotropic although most flowerheads will face east.

Growth Stages

The total time required for development of a sunflower plant and the time between the various stages of development depends on the genetic background of the plant and the growing environment. When determining the growth stage of a sunflower field, the average development of a large number of plants should be considered. This staging method can also be used for individual plants. The same system can be used for classifying either a single head or branched sunflower. In the case of branched sunflower, make determinations using only the main branch or head. In stages R7 through R9, use healthy, disease-free heads to determine plant development if possible since some diseases can cause head discolouration.

Stage Description
VE -  Vegetative Emergence Seedling has emerged and the first leaf beyond the cotyledons is less than 4 cm long.
V (number) Vegetative Stage  i.e.: V1, V2 etc
     
These are determined by counting the number of true leaves at least 4 cm in length beginning as V1, V2, V3, V4, etc. If senescence of the lower leaves has occurred count leaf scars (excluding those where the cotyledons were attached) to determine the proper stage.
R1 -  Reproductive Stages The terminal bud forms a miniature floral head rather than a cluster of leaves. When viewed from directly above the immature bracts form a many-pointed star-like appearance.
R2 The immature bud elongates 0.5 to 2.0 cm above the nearest leaf attached to the stem. Disregard leaves attached directly to the back of the bud.
R3 The immature bud elongates more than 2.0 cm above the nearest leaf.
R4 The inflorescence begins to open. When viewed from directly above immature ray flowers are visible
R5 (decimal)
i.e.: R5.1, R5.2 etc
This stage is beginning of flowering. The stage can be divided into sub-stages dependent upon the % of the head area (disk flowers) that has completed or is in flowering. ex: R5.3 (30%), R5.8 (80%) etc.
R6 Flowering is complete and the ray flowers are wilting.
R7 The back of the head has started to turn a pale yellow colour.
R8 The back of the head is yellow but the bracts remain green.
R9 The bracts become yellow and brown. This stage is regarded as physiological maturity.

Dwarf hybrid varieties mature 6 to 13 days earlier than conventional hybrid varieties.

 

Field Selection

Crop Rotation

Sunflowers grow best on loam, silty loam and silty clay loam soils with good drainage. Sunflowers have a low to medium tolerance of saline conditions, and therefore soils with high levels of salinity should be avoided. Sunflowers are sensitive to herbicide residues such as Lontrel and Pursuit. Consult the product label or the current MAFRI Guide to Crop Protection for specific details.

Crop rotation when growing sunflowers is very important. Sunflowers are very susceptible to sclerotinia as are canola and beans. Refer to the section on Diseases for further details on all diseases and crop rotation.

 

Variety Information

Variety Selection

Variety performance, acreage, seeding date and crop rotation effects on yield. 

 

Seeding

Treatments

Seeds can be treated with a fungicide to control downy mildew but there are no registered treatments for seedling blight. For specific seed treatment information, consult the current Guide To Field Crop Protection.

Dates

Sunflower seeding should begin anytime after May 1 and ideally be finished by June 1. Seedlings are relatively frost-tolerant up to the 4-leaf stage. Confection varieties are longer maturing than oilseed types. If seeding is delayed into the first week in June, switching to oilseed types is recommended as well as choosing earlier-maturing varieties.

Rates

Seeding rate for sunflowers depends on sunflower type. Oil-type sunflower populations range from 20,000 - 22,000 plants per acre (0.6 plants per ft2) but confection-type sunflowers should not exceed 18,000 plants per acre (0.4 plants per ft2) to ensure large seed size. Seeding rates for both oil and confection-type sunflowers should be adjusted when germination is low and for the number of weed control harrowing operations expected. Refer to Tables 1 and 2 below for information on plant density as well as seed size and weight.

Table 1. Seed Density as a Function of Row Spacing

Row Spacing
(inches)

16 18 22 30 36
Plants per Acre

Average Seed Spacing Within Row
(inches)

16,000
18,000
20,000
23
20
18
20
17
16
16
14
13
12
10
9
10
9
8

Table 2. Sunflower Seed Size and Associated Seed Weight

Oil-Type Sunflowers

Confection-Type Sunflowers

Seed Size Seeds per Pound Seed Size Seeds per Pound
No. 2 5000-6000 Medium 4000-5000
No. 3 6000-7000 Large 3000-4000
No. 4 7000-9000 Extra Large 2000-3000

Solid Seeding

Recommended row spacing for solid seeding is 10 to 14 inches for both confection- and oil-type sunflowers. Plant populations should remain the same as stated above regardless of row spacing. The sunflower plant will compensate for differences in plant population through changes in seed and head size. These changes are more noticeable in confections and caution should be taken when calculating the seeding rates.

Seeding Depth

Sunflowers need to be placed in moisture but not deeper than 3 inches (7.6 centimetres). The ideal seeding depth is 1.5 to 2 inches (3.8 to 5 centimetres) deep. Planting equipment should firm the soil over the seed row to maintain a moist seedbed.

 

Fertilizer Recommendations

General

Have your soil tested for specific recommendations on fertilizer rates. Phosphate and potassium should be side banded to the sunflower row, along with some or all nitrogen. Nitrogen is often banded between the rows after planting. If soil analysis is not available, a general recommendation is as follows:

Nitrogen (N)

Apply 0-30 lb/acre N following fallow or legume breaking, 30-55 lb/acre N following grass and grass-legume breaking and 55-90 lb/acre N following stubble.

Nitrogen deficiency symptoms are reduced growth (plant height) and general chlorosis, with the lower leaves showing a greater degree of chlorosis than the upper leaves.
 

Phosphate (P2O5)

Apply phosphate at 30-40 lb/acre P205.

Phosphate deficiency symptom are reduced growth and dark-grey necrosis of the lower leaves of the plant.
 

Potassium (K2O)

On sandy textured or organic soils, apply potassium at rates of 15-30 lb/acre K20 in a sideband or 30-60 lb/acre K20 broadcast.

Potassium-deficiency symptom are yellowing, with large necrotic patches on the oldest leaves.
 

Sulphur (S)

Apply sulphate sulphur at 20 lb/acre on well-drained soils. Sulphur deficiency may occur in many soils and in any area of the province. A soil test is recommended to establish the available sulphur status of fields.

Sulphur deficiency symptom are general chlorosis of the plant, with the youngest leaves showing a greater degree of yellowing than the older leaves.

Sunflowers take up and remove modest levels of nutrients compared to barley or canola. Table A indicates the range of nutrients taken up and removed by a crop yielding 2000 lb/acre.

Table A. Nutrient Uptake and Removal by Sunflower

Sunflowers at 2000 lb/acre Nitrogen
(lb N/acre)
Phosphorus
(lb P205/acre)
Potassium
(lb k20/acre)
Sulphur
(lb S/acre)
Uptake1 67-82 23-28 33-41 8-9
Removal2 48-59 14-18 11-13 4-5
Uptake1 = total nutrients taken up by the crop
Removal2 = nutrients removed in the sunflower seed

Compiled by the Canadian Fertilizer Institute

Soil Test Recommendations

Fertilizer recommendations based on soil testing were developed and used by Manitoba Agriculture, Food and Rural Initiatives.

Recommendations are based on a 0 to 6-inch (0 to 15.2 centimetre) sample for phosphorus and potassium, and on a 0 to 6-inch (0 to 15.2-centimetre) sand 6 to 24-inch (15.2 to 61-centimetre) sample for nitrate-nitrogen and sulphate-sulphur. The fertilizer recommendations are listed in Tables B and C.

Table B. Nitrogen Recommendations for Sunflowers (based on spring band application)

Target Yield
(lb/acre)

2,500 2,250 2,000 1,750

Fall Soil N03-N

 
lb/acre
in 0-24 in.
Rating

Nitrogen Recommendation
(lb/acre)

20 VL 200 150 100 50
30 L 170 120 70 15
40 M 140 90 40 0
50 M 115 65 10 0
60 H 85 35 0 0
70 H 55 5 0 0
80 VH 25 0 0 0
90 VH 0 0 0 0
100 VH+ 0 0 0 0

Germinating sunflower seeds are sensitive to fertilizer placed with the seed. When sunflowers are seeded with row equipment, all phosphate and potash should be side banded 2 inches (5 centimetres) beside and below the seed at time of seeding. Some or all of the nitrogen may also be side banded. The total amount of fertilizer material side banded should not exceed 300 lb/acre. When sunflowers are solid-seeded in 12- to 24-inch (30.5 to 61-centimetre) row spacing, up to 25 lb/acre P205 can be applied provided all fertilizer runs are left operating. If all phosphate must be placed with seed, the amount of phosphate should not exceed 15 lb per acre P205 for 12-inch (30.5-centimetre) row spacing, 10 lb per acre P205 for 18-inch (45.7-centimetre) row spacing and 5 lb/acre P205 for 24-inch (61-centimetre) row spacing. Nitrogen requirements not side-banded should be placed away from the seed as a band or broadcast application.

Table C. Phosphorus, Potassium and Sulphur Recommendations for Sunflower Based on Soil Test Levels and Placement

Soil Phosphorus
(sodium bicarbonate P test)
Fertilizer
(P20 lb/acre)
Soil Potassium
(ammonium acetate
K test)
Fertilizer
(K20 lb/acre)
Soil Sulphate
(Sulphur in
0-24 in.)
Fertilizer S (lb/acre)
Ppm lb/acre Rating Sb1 ppm lb/ac Rating Sb1 PPI2 lb/ac rating N/A3
0 0 VL 40 0 0 VL 30 60 0 VL 20
  5 VL 40 25 50 VL 30 60 5 VL 20
5 10 L 40 50 100 L 15 30 10 VL 20
  15 L 35 75 150 L 15 30 15 L 20
10 20 M 30 100 200 M 0 0 20 L 20
  25 M 20 125 250 M 0 0 25 M 20
15 30 H 15 150 300 H 0 0 30 M 20
  35 H 10 175 350 H 0 0 35 H 0
20 40 VH 10 200 400 VH 0 0 40 VH 0
20+ 40+ VH+ 10 200+ 400+ VH+ 0 0 40+ VH+ 0
Sb1 = side banded
PPI2 = broadcast and preplant incorporated
N/A3 = placement does not influence effectiveness of sulphate forms of sulphur fertilizer

Plant Tissue Analysis

Plant tissue analysis is an important tool is assessing nutrient status of the growing crop. Following are plant tissue analysis interpretive criteria used by the former Manitoba Agriculture Provincial Testing laboratory. These levels should be used for the top 1 to 3 most mature leaves collected at the bud stage. Consult with your soil and plant tissue laboratory for guidelines when sampling at other stages of growth.

Special Considerations

Sunflowers have deep tap roots that can obtain water and nutrients 5 to 6 feet (1.5 to 1.8 metres) deep in the soil. These reserves of water and nutrients are unavailable to most other annual crops, making sunflower a good rotational crop.

Sunflowers are very susceptible to seed-placed fertilizer injury. To avoid seedling injury from fertilizer, best results are obtained by placing starter fertilizer in a band 2 inches (5 centimetres) below and beside the seed. The remainder of the fertility should be applied in one of the following ways:

  1. Broadcast incorporated prior to seeding
  2. Side dressing in crop (nitrogen)
  3. Fall or spring banding

Table D. Sunflower Tissue Analysis Interpretation

Nutrient

Content Rating
Low Marginal Sufficient High Excess
Nitrogen % (N) 1.4 1.5-1.9 2.0-3.4 3.5-3.9 4.0
Phosphorus %  (P) 0.14 0.15-0.24 0.25-0.49 0.5-0.79 0.8
Potassium % (K) 0.9 1.0-1.4 1.5-2.9 3.0-4.9 5.0
Sulphur % (S) 0.14 0.15-0.19 0.2-0.39 0.4-0.99 1.0
Calcium % (Ca) 0.19 0.2-0.29 0.3-1.9 2.0-2.4 2.5
Magnesium % (Mg) 0.09 0.1-0.19 0.2-1.4 1.5-1.9 2.0
Zinc ppm (Zn) 11 12-14 15-69 70-149 150
Copper ppm (Cu) 2 3-5 6-24 25-74 75
Iron ppm (Fe) 14 15-19 20-249 250-499 500
Manganese ppm (Mn) 9 10-14 15-99 100-249 250
Boron

No provincial guidelines developed. Consult analytical companies.

Field Scouting

Check For Potential Problems Regularly

Field scouting involves walking into the field and assessing the overall health of the crop.  While field scouting, look for plants showing symptoms of insects or diseases, and watch for insects or diseases that may be evident in the field.  If a particular insect or disease appears to be of concern in the field, then it is necessary to do a more thorough examination of that specific insect or disease to determine the extent of the problem and whether control measures are possible and economical.  Information in the following sections on insects and diseases will provide the details on how to do a more thorough examination for each of the major insect and disease problems in sunflowers, and provide advice on if and when controls are economical.

Check For Beneficial Organisms

In addition to looking for pests and problems when field scouting, also watch for beneficial organisms, such as pollinators, predators and parasites of potential pests.  Pollinators can increase yield by enhancing pollination of sunflowers, and natural controls can keep some potential pests below damaging levels. 

Pollination

Sunflower yields benefit from honeybee pollination. Sunflowers produce a large supply of nectar for honeybees, and therefore colonies located near the field will actively forage and pollinate the crop.

Try to Minimize Harm to Beneficial Organisms if Pests Need to be Controlled

If some pest levels are above economic threshold, and a pesticide application would be economical, consider applying the pesticide at a time and in a method that minimizes harm to the beneficial insects in the field.  For example, if applying an insecticide to a sunflower field that is flowering, apply the insecticide in the evening or early morning when the bees are not foraging.  If you are aware of any beehives nearby, contacting the beekeeper in advance (i.e. 48 hours) of insecticide application will allow the beekeeper to move or protect bee colonies from insecticide damage.

Scouting Calendar For Sunflowers

Stage of Sunflowers Insects to Look for When Monitoring Diseases to Look for When Monitoring
Seedling Cutworms, wireworms, sunflower beetles Assess incidence of downy mildew
Vegetative States Sunflower beetles, thistle caterpillars, stem weevils Look for first appearance of rust
Flowering Stages Seed weevils, banded sunflower moth, lygus bugs, honey bees Watch for factors conducive to head blight infection (Sclerotinia) ex: areas of saturated soil

 

Weeds

In sunflowers, weeds can be controlled by using pre-emergent herbicides, harrowing before crop emergence, inter-row cultivation when the crop is in the 5 to 6 leaf stage and post-emergent herbicides. Weeds should be removed within the first 4 weeks of crop growth to minimize yield losses. 

Links:

 

Insects

Many insects can reduce sunflower yields, however only some insects build up high enough number to cause economic damage in sunflowers.

Links:

 

Sunflower Beetle

 

Diseases

For information on varietal differences to disease susceptibility consult Seed Manitoba.

 

Links:

sunflower headrot
Sclerotinia Head Rot

Harvesting

Timing

Sunflowers are usually the last crop to be harvested in fall, since fall frosts are necessary for drying down the crop (unless a desiccant is used). The period between maturity and harvest should be kept as short as possible to minimize losses from bird damage and head-rot diseases.

Desiccation

Chemical desiccation is used to dry down the stalk and sunflower heads. Desiccation is effective before a killing frost in enhancing head dry-down but should not be applied before the back of the sunflower head turns a deep, dark yellow and the bracts are brown and dry. At this stage the plant is said to be physiologically mature and seed moisture will be 20 to 50%. Refer to the current Guide to Field Crop Protection for details on desiccation products.

Combining

Sunflowers can be safely combined when the seed moisture is below 18-20%. However, allowing sunflowers to dry-down to a moisture content of 9.5 -12% reduces the need for drying on-farm.  At 12% moisture content, seed can be stored in bins with aeration. Any moisture content over 12% will require drying to avoid spoilage. Oil-type sunflowers can be dried with temperatures of 71º to 104º C (160ºF to 220ºF) but confection-type sunflower seed may scorch or wrinkle with these temperatures. Sunflower seed should be cooled before storage, since even sunflowers at 8.5% moisture can spoil if stored when warm.

Sunflowers can easily shatter if heads are very dry, and therefore combine speed must be slowed accordingly. Cylinder speeds range from 300-500 rpm, with concave settings quite open (1 inch in front and 3/4 inch in rear) to minimize seed breakage and dehulling. Using the slowest seed cylinder speeds with the largest openings will result in the least seed damage.

Harvesting Attachments

Combines that are suitable for harvesting small grain will be adequate to harvest sunflowers. A proper header attachment is necessary to reduce shattering losses and harvest efficiently.

There are two types of attachments:

  1. The pan header, which is mounted on traditional straight cut header and is suitable for both row crop and solid seeding
  2. The all crop header, which is only suitable for row crop planting  

Links:

 

Production Economics

Quality

The same grade standards, established by the Canadian Grain Commission, apply to both confection and oil type sunflowers. However, confection contract standards are considerably higher than those established for oil type sunflowers. Confection sunflower contracts usually require 10% moisture, less than 1% sclerotia, less than 1% dark roast, 155g/0.5 L (approximately 25 lb/bu) test weight and the seeds must be larger than 22/64-inch round-hole sieve.

Since many sunflowers are commonly sold into the United States, the table below outlines the grade standards for the United States which is a large market for sunflower seeds.

Sunflower Grades from the United States (Confection-Type)

Grade

Minimum Test Weight per Bushel
(pounds)

Maximum Limits of Damaged Sunflower Seed

Heat Damaged
(percent)

Dehulled Seed
(percent)

Total
(percent)

U.S. No. 1 25.0 0.5 5.0 5.0
U.S. No. 2 25.0 1.0 5.0 10.0
U.S. Sample Grade
  1. Does not meet the requirements for the grades U.S. No. 1 or 2
  2. Contains 8 or more stones which have an aggregate weight in excess of 0.20 percent of the sample weight, 2 or more pieces of glass, 3 or more crotalaria seeds, 2 or more castor beans, 4 or more particles of unknown foreign substance(s), or a commonly recognized harmful or toxic substance(s), 10 or more rodent pellets, bird droppings or equivalent quantity of other animal filth per 600 grams of sunflower seed
  3. Has a musty, sour, or commercially objectionable foreign odour
  4. Is heating or otherwise of distinctly low quality


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