Tips for a Successful Sunflower Harvest
Sunflower should be under 10% moisture – between 9% and 10% is best – for proper storage. Oil sunflower moisture content should be 10% or less for winter storage and 8% or less for storage during warmer months. Getting there can be a balancing act at harvest – wait too long for natural dry down, and sunflower standing in the field can become too dry and vulnerable to quality deterioration and shelling out. Cut too early, and there’s greater chance for (deterioration during storage) if seed moisture is too high.
Many experts advise combining flowers at 12-15% moisture, and using natural air drying to get stored seed moisture under 10%. In the High Plains, seed moisture that’s too dry – standing sunflower down to 5%, for example – is often more of a problem then cutting ‘flowers too damp. If harvest conditions are too dry, consider harvesting at night or very early/late in the day when humidity is higher.
Some tips for a successful sunflower harvest:
Maturity: The sunflower plant is physiologically mature when the back of the head has turned from green to yellow (although stay-green hybrids may stay green longer) and the bracts are turning brown (Stage R-9) about 30 to 45 days after bloom, and seed moisture is about 35%. Generally, when the head turns brown on the back, seeds are usually ready for harvest.
Threshing goal: Have the header platform raised high enough to take in the heads, minimizing stalks as much as possible. The overall goal of the threshing process should be passing the head nearly intact through the combine, or in a few large pieces, with all developed seed removed from the head. If the head is being ground up into small pieces, there will be excessive trash in the grain. Adding catch pans to the front of a platform (wheat) header and/or modifying the reel is recommended to improve harvest efficiency and reduce losses. Twelve-inch pans are best for 30-inch row spacings; 9-inch better for other row sizes and solid seeding.
Common threshing mistake: Waiting to harvest and seeds become too dry and shell out. Harvesting at 10% moisture or less also makes your combine more vulnerable to fire. Better: combine at 14-15% moisture and use air/dry down to under 10% moisture.
Forward speed: Combine forward speed should usually average between 3 and 5 miles per hour. Forward speed should be decreased as moisture content of the seed decreases to reduce shatter loss as heads feed into the combine. Faster forward speeds are possible with seed moisture between 12 and 15%.
Fan speed: Air speed should be lower, due to the lighter weight of sunflowers (oils weigh about 28 to 32 lbs/bu, confection 22 to 26 lbs/bu). Excessive wind may blow seed over the chaffer and sieve, and seed forced over the sieve and into the tailings auger will be returned to the cylinder and may be dehulled. Set the fan so only enough air flow is created to keep trash floating across the screen/sieve. Concave settings should generally be run quite open. On a rotary combine, a rotor-to-concave setting of 3/4 to 1” is appropriate. A bottom screen or lower sieve of 3/8” and a top screen/upper sieve of 1/2 to 5/8” is typical. Seed size may be smaller than average this year due to drought, adjust fan speed and other settings accordingly.
Cylinder/rotor speed: Slow cylinder/rotor speed to 250 to 400 rpm. Normal cylinder speed should be about 300 rpm (for a combine with a 22” diameter cylinder to give a cylinder bar travel speed of 1,725 feet per minute). Speed will vary depending upon crop conditions and combine used. Combines with smaller cylinders will require a faster speed and combines with a larger cylinder diameter will require a slower speed.
A rotary combine with a 30” cylinder will need to be operated at 220 rpm, and a combine with a 17” cylinder will need to operate at 390 rpm to, have a cylinder bar speed of 1,725 feet per minute.
If a combine cylinder operates at speeds of 400 to 500 rpm giving a cylinder bar speed of over 2,500 feet per minute, very little seed should be cracked or broken if the moisture content of the seed is above 11%. Cylinder bar speeds of over 3,000 feet per minute should not be used because they will cause excessive broken seed and increased dockage.
Concave adjustment: When crop moisture is at 10% or less, conventional machines should be set open to give a cylinder to concave spacing of about 1” at the front of the cylinder and about 0.75” at the rear. A smaller concave clearance should be used only if some seed is left in the heads. If the moisture percentage of the crop is between 10 and 12%, rather than increase the cylinder speed, the cylinder-to-concave clearance should be decreased to improve threshing. If seed moisture exceeds 15 to 20%, a higher cylinder speed and a closer concave setting may be necessary, even though foreign material in the seed increases.
Seed breakage and dehulling may be a problem with close concave settings. Make initial adjustments as recommended in the operator's manual. Final adjustments should be made based on crop conditions.
Rotary combines should be set to have a rotor-to-concave spacing of about 0.75 to 1”. It is usually best to make initial settings as recommended in the operator's manual. Final adjustments should be made based on crop conditions.
Rule of thumb for harvest loss: 10 seeds per square foot (don’t forget heads that have seed left in them) represents a loss of 100 pounds per acre, assuming seed loss is uniform over the entire field. Harvest without some seed loss is almost impossible. Usually a permissible loss is about 3%. Loss as high as 15 to 20% has occurred with a well-adjusted combine if the ground speed is too fast, resulting in machine overload.
Are your bins ready? Bins with perforated floors work better for drying sunflower than those with ducts. Aeration is essential, especially in larger bins. Aeration may be accomplished with floor-mounted ducts or portable aerators. Aeration fans should deliver 1/10 to 1 cfm per cwt of sunflower. If aeration is not available, sunflower should be rotated between bins to avoid hot spots developing in the stored grain.
Cleaning before storage: When excessive trash is present in the harvested grain, cleaning before storage can greatly reduce incidence of storage problems. Ambient air can be used to cool and dry sunflower. If heated air is used, generally a 10 degree F. increase in temperature over ambient is sufficient to increase rate of drying. Be aware that sunflower dries more rapidly than corn or soybeans, and should be monitored to avoid overdrying.
Watch for moisture rebound: When taking a moisture reading on sunflower seeds that are being dried in a bin, keep in mind that the hull dries faster than the kernel. Thus, a moisture reading taken on sunflower being dried may be artificially low; for example, a moisture meter may give a reading of 10%, then climb back up to 12% the next day. To get a more accurate reading, place some seed in a covered jar overnight and take a moisture reading the next day, after the hull and kernel moisture have equalized.
Prepare for fire hazards: Always keep in mind that sunflower is an oil-based crop, and fine fibers from sunflower seeds pose a constant fire hazard, especially when conditions are dry. Keep combine and grain dryer free of chaff and dust (consider having a portable leaf blower on hand for this). Keep a small pressure sprayer or container filled with water on hand in the combine in case of fire. If the threat of extreme dry conditions and combine fires persists, try nighttime harvesting, when humidity levels are higher.
Sources: North Dakota State University Extension Service, Kansas State University Extension Service
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