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Sunflower Combining Clinic

Wednesday, September 17, 2003
filed under: Harvest/Storage

Whether you’re new to growing sunflower or an old hat with the crop, a pre-harvest checkup before you drop the header and go is always a good idea. So here’s our sunflower combining clinic— bring your own folding chair and refreshments.

Forward speed

Optimum forward speed will vary depending upon sunflower yield and seed moisture content, but should usually average between three and five 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 if seed moisture is between 12 and 15%, a window where seeds will thresh from the head very easily as they pass through the cylinder. Higher speeds should not overload the cylinder and the separating area of most combines, except in an extremely heavy crop. If seed is being thrown out the back, slow down the machine and air flow rate.

Cylinder speed

After the sunflower heads are separated from the plants, they should be threshed at a cylinder speed operating as slow as possible. Normal cylinder speed should be about 300 rpm, depending upon the condition of the crop and the combine being used. This cylinder speed is for a combine with a 22-inch diameter cylinder to give a cylinder bar travel speed of 1,725 feet per minute.

Combines with smaller cylinders will require a faster speed and combines with a larger cylinder diameter will require a slower speed. Rotary combines as well as conventional machines should have similar cylinder travel speeds. A rotary combine with a 30-inch cylinder will need to be operated at 220 rpm to have a cylinder bar speed of 1,725 feet per minute. A combine with a 17 inch cylinder will need to operate at 390 rpm to have a cylinder bar speed of 1,725 feet per minute.

You can increase cylinder speed a bit when seed moisture is higher. If seed moisture content is above 11%, there should be little cracked or broken seed with a combine cylinder operating at speeds of 400 to 500 rpm, giving a cylinder bar speed of over 2,500 feet per minute. Keep cylinder bar speed below 3,000 feet per minute, however, to minimize excessive broken seed and increased dockage.

Concave adjustment

Sunflower threshes relatively easily. 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 after passing through the cylinder.

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 may increase. 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’s usually best to make initial settings as recommended in the operator's manual, with further adjustments made based on crop conditions.

Fan adjustment

Oil and confection sunflower weigh about 28 to 32 pounds per bushel and 22 to 26 pounds per bushel, respectively. The seed is relatively light compared to other crops, so excessive wind may blow seed over the chaffer and sieve. Seed forced over the sieve and into the tailings auger will be returned to the cylinder and may be dehulled. Only enough wind to keep the trash floating across the sieve should be used. The chaffer and sieve should be adjusted to minimize the amount of material that passes through the tailings elevator.

When the combine is adjusted correctly to thresh sunflower seed, the threshed heads will come through only slightly broken and with only unfilled seed remaining in the head. Cylinder concaves and cleaning sieves usually can be set to obtain less than 5% dockage.

Proper setting is critical, especially for confection sunflower. Improper settings may crush the seed but leave the hull intact. The upper sieve should be open enough to allow an average seed to pass through on end or be set at 1/2 to 5/8” opening. The lower sieve should be adjusted to provide a slightly smaller opening or about 3/8” wide. Further adjustments will depend on the amount of material returning through the tailings elevator and an estimation of the amount of dockage in the grain tank. Some operators are able to adjust and operate their machine to allow only 2 to 3% dockage in the seed.

Field loss

Harvested yield may be increased by making necessary adjustments following a determination of field loss. The three main sources of loss:

1) In the standing crop ahead of the combine due to shattering;

2) Header loss as the crop enters the machine;

3) Threshing and separating.

Loss occurring in any of these areas may be estimated by counting the seed on the soil surface in a square foot area. Twenty oilseed sunflower seeds per square foot is approximately one hundredweight (cwt) per acre loss if seed loss is uniform over the entire field. When confectionary sunflower is harvested with larger seed size, then 10 to 12 seeds per square foot would be a harvest loss of approximately one hundredweight per acre.

Harvest without some seed loss is almost impossible: usually a permissible loss is about 3%. Loss as high as 15 to 20% can occur with a well adjusted combine if the ground speed is too fast, resulting in machine overload. – Tracy Sayler, with information from North Dakota State University and Colorado State University

Quick Tips to Harvesting Sunflower, Corn and Soybeans

Sunflower Corn Soybeans


Maturity Bracts yellow/brown;

Little green remaining

back of heads. Kernel black layer forms

at tip of kernels; kernel

moisture about 30% Pods turn yellow to tan in color.

Beans begin to shrink and

separate from white

membrane inside pod.

Avoid this common

threshing mistake Combining too dry: heads will shell out. Pushing through the crop too fast; stalks ride over the sieves resulting in more separating loss. Combining too dry, which results in shattering.

Optimum Harvest

Moisture Combine at 14-15% moisture and dry down to under 10% moisture. 18%-23% 12%-15%. Under 12%, you risk cracks and splits.

Harvest equipment tip 12" pans best for 30" row spacings; 9” better for other row sizes and solid seeding.

All-crop header will work but is slower than corn head. Operation of cylinder/rotor can affect corn kernel damage more than any other setting. Have a sharp sickle; combine settings critical to avoiding cracks and splits.

Acceptable harvest loss About 3%, for oil sunflower, which is about 20 seeds/sq. ft or about 100 lb/acre. Try to keep it under 2%. Two kernels/sq. ft = 1 bu./acre. 1.5-2 bu./acre.

4 beans/sq. ft. = 1 bu./acre.

Storage moisture Below 10% for overwinter storage. 15% short-term,

13% or less long-term. 11-12%

Source: Duane Berglund, NDSU extension agronomist

When to consider a sunflower desiccant

If bird pressure is severe, disease levels are high, or lodging problems are occurring, the use of a harvest-aid desiccant for sunflower may be considered when the crop is mature and an early harvest would be an advantage.

Early drydown of sunflower plants may also slow or stop development of head rot and reduce sclerotia and destruction of seeds. Desiccation can also reduce head shattering, control weeds (especially large weeds like kochia and marshelder, resulting in less dockage and less wear and tear on combines) and ease crop drying with reduced drying costs.

Desiccant and application costs must be weighed with prospective advantages. Warm sunny days following a desiccant application are needed to give the best results.

Two types of desiccants can be used. These include paraquat (Gramoxone Max) and sodium chlorate (Drexel Defol) for use on oilseed and confectionary sunflower. Allow a minimum of 7 to 10 days prior to harvest to get maximum killing and drydown of the sunflower. Read and follow the label for rates and adjuvants to use.

Apply desiccant by air after the back of sunflower heads have turned yellow and the bracts are turning brown. Physiologically mature sunflower plants have a seed moisture content between 33 and 35%. Some sunflower hybrids now have a stay-green stalk characteristic, so go by the heads or seeds. Another way to help indicate if physiological maturity has occurred is to rub the chaffy material on the front of a sunflower head. If it rubs off easily, the plant is physiologically mature.

Keep it clean: fire potential greater when conditions, crop drier

Keep a clean work area when harvesting sunflower: Blow the combine and grain dryer setup with an air hose daily. If dust collects on the machine, remove it regularly to eliminate the chance of fire— the potential of which is even greater when harvest conditions and the crop are drier.

It's a good practice to keep a small pressure sprayer filled with water on hand in the combine in case of fire. Indeed, a $25 fire extinguisher is a good investment if it can prevent the destruction of a $100,000 combine.

If the threat of extreme dry conditions and combine fires persists, try nighttime harvesting, when humidity levels are higher. “f the crop is dry and the relative humidity is low, we recommend not harvesting during the afternoon, but in the early morning or after sunset to minimize fire danger and get a cleaner seed sample,” says Roger Stockton, Kansas State University extension crops and soils specialist.

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