You planted your crop and nurtured it through to harvest, now is the time to think about gathering it in without leaving seed on the ground.
This article is about some of the issues to look for and think about, to reduce harvest losses and help to maximize that hard-won yield.
Are there acceptable harvest losses?
It’s almost impossible to harvest any commercial crop without leaving some seed on the ground.
To achieve zero losses would require the combine to be moving at such a slow pace that winter would arrive long before you got anywhere near finishing the crop.
The key is to achieve a balance between a suitable work rate and limiting harvest losses to acceptable levels.
Harvest losses around 3-5% are generally considered to be commercially acceptable, which on a two tonne crop would be around 75-100 kg of seed per hectare left behind, which is still enough but considering losses can be as high as 20% with an incorrectly set up combine, you can see why 3-5% is considered tolerable.
Before we look at reducing harvest losses, we need to be able to measure and assess where they are coming from.
Measuring harvest losses
Check pre-harvest losses by counting seeds on the ground in front of the combine, before the crop has been harvested, and again behind the combine.
This will allow you to determine the number of losses and where they are taking place.
As a rough guide, 100 seeds per square meter is equivalent to around 100 kilograms per hectare of crop, don’t forget heads that have seed left in them.
Adjust seed counts taken behind the combine for the concentrating effect from the width of the cut.
Where do harvest losses occur?
A successful harvest begins at planting, by selecting suitable seed varieties then making appropriate agronomic decisions to produce a uniform crop that will feed into the combine easier, resulting in less head and seed losses and less stalk.
Once harvest is underway, seed can be lost at several places and losses should be assessed at each location so that corrective action can be taken.
Typically, losses occur in three places.
Pre-harvest losses
This is where seed is lost or shed before the combine harvests the crop, and can be caused by birds or mammals eating seed, plants falling over and heads not being picked up by the combine later on, or by heads rubbing together in the wind causing seeds to become dislodged.
Pre-harvest losses can be reduced by being prepared to harvest the crop when it is ready and finishing in a timely manner.
Waiting for seeds to become too dry increases the risk of these pre-harvest losses so it is generally better to combine at 14-15% moisture and then dry the crop if facilities are available.
Header losses
Seed and heads are lost at the combine header and are not gathered into the machine, the rate of losses depends on the skill of the combine driver, crop condition and type of header being used.
The main objective is to gather heads with minimal stalk entering the combine and minimal seed loss from shattering.
This can be achieved by raising the combine header high enough to take in the heads while reducing the amount of stalk and keeping the head intact, so it passes through the combine whole or in a few large pieces.
One sunflower head contains a lot of seed so making sure they all pass through the combine will do a lot to reduce sunflower harvest losses.
Sometimes header performance can be dramatically improved simply by reducing the forward speed, being patient during harvest will often pay dividends.
Most header types will cope with sunflowers if set up correctly but investing in specialty sunflower headers can be a good investment, there are some well-made and competitively priced models currently available.
Combine threshing losses
Once the sunflower head is gathered into the combine, incorrect drum, concave and sieve settings can lead to excessive losses because seed is not effectively threshed out of the heads or is allowed to pass over the back and is ejected along with the trash.
The aim is to get a completely threshed head onto the straw walker in one piece. Although different combine harvesters will have different specific optimal settings for sunflowers, the general guide is to combine at a reasonable forward speed, use a slow cylinder speed, have concaves well open, use a low airspeed and harvest when seed moisture is in the low teens.
| Combine speed | Aim for around 5-8 kilometers per hour, if seed moisture content is low then slower speeds should be used to reduce shatter loss, while higher speeds can be used with higher moisture content seed. |
| Cylinder speed |
Sunflowers thresh relatively easily; cylinder speed should be set only fast enough to thresh seeds out of the head. High cylinder speed causes dehulling and breaking of seeds, and the chaffer, sieve, and tailings return may become overloaded with small pieces of broken heads. |
| Concave spacing |
If the crop is dry the concave should be wide open, lower the concave clearance if seed is left in the head after threshing. Under most conditions, it is best to decrease the concave clearance rather than increase cylinder speed to get more complete threshing. Aim for whole sunflower heads leaving the combine without seeds in them. |
| Airspeed |
Sunflower seeds are light so fan airspeed should be low, too high and it will blow seed over the 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 airflow is created to keep trash floating across the sieve. |
When are sunflowers ready to harvest?
Sunflowers can be desiccated to allow for an earlier harvest, apply desiccants when plants have reached physiological maturity which is identified when the back of the head has turned from green to yellow, the bracts are turning brown (Stage R-9), and seed moisture is about 35%.
Generally, when the head turns brown on the back, seeds are usually ready for harvest.
Top tips for a successful sunflower harvest
- Don’t wait for the crop to dry down too much.
- Resist the urge to combine too fast, patience is a virtue.
- Keep the header high to reduce the amount of stalk passing through the combine.
- Make one adjustment at a time, then check losses after each change.
- Use a sunflower header.
- Make sure combines have earth straps touching the ground, chains usually work well.
- Frequently blow down dust to reduce fire hazards.
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