Other Crops: Sunflower

Excerpt from Agronomy Guide for Field Crops (Chapter 9)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Tillage
3. Variety Selection
4. Planting
• Rotation
5. Fertility
• Phosphate and Potash Recommendations for Sunflowers Based on OMAFRA-Accredited Soil Tests - Table 9-3
6. Harvest and Storage
• Harvest
• Storage
7. Weed Control
8. Insects
9. Disease
• White Mould (Sclerotinia)
10. Updates on Other Crops: Sunflower

Introduction

Sunflowers have been grown in Ontario for several decades. The main market for Ontario sunflowers has been for the birdseed and confectionery markets. Both black seeded and striped sunflower seeds are sold into the birdseed markets. There are no sunflower oilseed crushing markets in Ontario. Acreage in Ontario has varied from 500-1,000 ha (1,235-2,470 ac) per year during the past 10 years.

Tillage

Sunflowers require a firm, moist seedbed that is weed free. Conventional tillage is usually preferred over no-till, as the tillage is beneficial to control weeds.

The best crop performance is usually on medium-textured soils that are naturally well drained: loam, silty loam or silty clay loam. Sunflowers can also grow well on sandy soils, but yield will be reduced under drought conditions. Avoid poorly drained soils as they will delay planting, slow the rate of growth and cause a higher risk of disease.

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Variety Selection

There are no sunflower variety trials conducted in Ontario. Variety testing is conducted through the National Sunflower Association of Canada at P.O. Box 382, Morden, MB, R6M 1A4.

Sunflowers can be classified as either oil or confectionery. Oil-type sunflowers have black hulls and can be conventional hybrids, dwarf hybrids, mid-oleic or open pollinated varieties. Dwarf hybrids mature 6-13 days earlier than conventional hybrids. Open pollinated sunflower (Sunola) varieties are shorter and require less heat to mature than normal sunflowers but they do not have good disease resistance.

Non-oil-type sunflowers have striped hulls and are grown for the human food market. Only the largest of the confection sunflowers are used for human consumption, but these varieties have little tolerance for bird or insect damage.

Hybrids have many advantages over open pollinated varieties. Hybrids have approximately 20% greater yield, better disease resistance (especially downy mildew, rust and Verticillium wilt), a high degree of self-compatibility, which reduces the need for bees to pollinate, and more uniform height and moisture content at harvest.

Sunflowers are tall, broad-leafed, usually single-stemmed plants, with one head per plant. The stem is hairy and becomes fibrous as the plant matures. Plants are heliotropic, which means that the heads face east by morning and west by evening, following the day's sun. They have a deep taproot system, which allows them to handle drought and access to deep water and nutrient supply that is generally unavailable for many other annual crops.

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Planting

Sunflowers are usually planted in early May, similar to corn, and usually bloom in late July. They require approximately 100-120 days to mature. Seedlings are relatively tolerant to frost up to the four-leaf stage. A delay in planting beyond May 15 will increase the risk of frost damage prior to maturity in the fall. When delays in planting are unavoidable, use early-season hybrids/varieties.

Optimum planting depth is 3-5 cm (1^1/4-2 in.) and not more than 8 cm (3^1/4in.), in moist soil. Shallow planting is suited to cold, wet, fine-textured soil. Sunflowers are prone to lodging in heavier soils or where there is heavy rain and wind.

The ideal row width is 60-90 cm (24-36 in.). Use a corn planter with appropriate seed adjustments or a grain drill with some of the runs plugged. Grain drills typically give poorer emergence.

The recommended seeding rate is 40,000-60,000 plants/ha (16,000-24,000 plants/ac). Confection sunflowers should not be seeded greater than 18,000 plants/ac, to help encourage large seed size. Plant 25% more seed than the desired plant population. Narrow row spacing (18-25 cm or 7-10 in.) and solid stands increase the risk of white mould with humid Ontario climate. Less lodging occurs if rows are planted east to west, as sunflower heads face to the east and cause plants to bend toward the east.

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Rotation

Do not plant sunflowers in the same field more than once every 4-5 years, due to disease build-up. Canola, field beans, soybeans and buckwheat are also hosts of white mould (Sclerotinia); monitor rotations with these crop closely or avoid them altogether.

Volunteer sunflowers can also be a problem in some crop rotations. Sunflowers are sensitive to atrazine and other herbicide carryover, such as from some of the sulphonylurea (ALS) herbicides.

Fertility

The recommended amount of nitrogen for sunflowers is 90 kg/ha (80 lb/ac). The most efficient use of nitrogen is when most of the nitrogen fertilizer is applied as a side-dress before the plants are 30 cm (12 in.) tall. Test your soil to determine the phosphorous and potash requirements (see the section Soil Testing). See Table 9-3. Phosphate and Potash Recommendations for Sunflowers Based on OMAFRA-Accredited Soil Tests.

100 kg/ha = 90 lb/ac

¹No expected agronomic response from additional application of nutrients. Ratings of "Excessive" may result in reduced yield or affect nutrient balance in crops. For example, additional phosphorus application to a soil>60 ppm phosphorus could induce a zinc deficiency on soils low in zinc and might also increase the risk of nitrate movement into groundwater, while additional potash application to a field already>250 ppm K soil test could induce magnesium deficiency on soils low in magnesium.

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Harvest and Storage

Harvest

Typical sunflower yields in Ontario range from 1,500-2,000 km/ha (1,300-1,800 lb/ac). Plants are ready for harvesting when the back of the heads turn yellow, and bracts around the head are brown, hard and dry. Seeds at this stage have approximately 50% moisture. Harvest is normally in September to mid-October.

In Ontario, if a crop is late maturing, drying will be facilitated by a killing frost. Use of a desiccant is therefore typically not required. However, early frost may reduce yield and oil content. To avoid this, harvest at a higher percentage moisture and dry seeds to reduce shatter loss and exposure to birds. Minimize the period between maturity and harvest to prevent bird damage and head rot.

Sunflowers are harvested with a combine equipped with a small grain head. Most combines are adapted with long seed-gathering pans extending in front of cutter bar to collect and salvage shattered seed. The reel is typically removed or raised for sunflower harvest. To prevent seed damage, use the slowest cylinder speeds with the largest openings. Reduce air flow to prevent seeds from being blown through the back.

After harvest, clean seed to remove trash. For proper storage, seed must contain 10% moisture or less. Dry higher moisture seed immediately after harvest. Sunflowers dry easily in conventional grain dryers. Confection types may wrinkle or be scorched. Allow to cool before storing.

Caution: Dry at low temperature because fine hairs and fibres from the seed coat could ignite when put through the drying fan.

In general, bins will hold 70% as much tonnage of sunflower as corn. They can be stored for short periods at 8.5%-12% moistures. Higher moisture or warm seeds may result in spoilage.

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Weed Control

Sunflower seedlings suffer from weed competition. If weeds are not controlled early in the season, crop performance is reduced. As sunflowers mature, they become more able to compete with weeds.

The crop can be harrowed before seedling emergence to remove emerging weeds before they become established. A light spring tooth harrowing can be done when sunflower seedlings are between the four- and six-leaf stage to remove late-emerging weeds. Harrowing is best done under hot, dry conditions to reduce crop damage. Inter-row cultivation is also recommended.

For herbicide recommendations, refer to OMAFRA Publication 75, Guide to Weed Control. (Order OMAFRA Publication 75)

Insects

Insects are typically not a problem in sunflowers.

Disease

White Mould (Sclerotinia)

White mould (Sclerotinia) can be a problem in sunflower production. Sclerotinia causes stalk rot (basal stem rot), midstem infections and head rot and leads to large yield reduction (see Plate 147). The organism can live in the soil for long periods, so do not plant sunflower in rotation with susceptible crops, especially if these other crops demonstrated symptoms.

Plate 147. Sunflower white mould causes basal stem rot, mid-stem infections and head rot in sunflowers.

Updates on Other Crops: Sunflower

No updates available at this time.

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