Harvest management of sunflower
Harvesting sunflowers can be challenging but, with attention to detail, a high quality sample can be achieved. In all markets, a quality sample is required, with discounts applied if the admixture is over 4% in the oilseed market and in the birdseed market there is a reluctance to purchase the product if it is not a clean bright sample.
Identifying physiological maturity
Physiological maturity occurs when the maximum seed weight has been reached. The crop can be harvested once sufficient dry down has occurred, where the seed moisture content is suitable for storage or delivery.
Physiological maturity is identified when the bracts surrounding the sunflower head change to brown. The seed moisture content at physiological maturity is usually between 30–40% and the crop is suitable for desiccation to aid in quicker dry down.
Pre-harvest desiccation can increase harvest speeds, reduce admixture in the grain sample and reduce the seed set of late ripening weeds. Diquat is the only herbicide registered for pre-harvest desiccation in sunflowers. An emergency use permit (PER13118) is in place for the use of glyphosate for pre-harvest desiccation and weed control in sunflowers (check the permit date before use).
The receival standard for moisture is 9%. Often, crops are not harvested until the moisture content is much lower, around 5–6%, which represents lost yield. Aim to harvest and deliver as close as possible to 9% moisture. Harvesting above 9% moisture will increase the risk of fire in storage.
Harvesting at low moisture contents (< 6%) may cause an increase in admixture as the plant stalks and heads become dry and brittle, easily shattering into small pieces. This added trash is difficult to separate from the seed and penalties apply for excess admixture.
Commence harvest when some 5–10% of heads are still soft (some cream colour on the back). This will reduce trash levels and enable a faster harvest speed. Don’t wait until all heads are black as low moisture levels may cause harvest difficulties.
Header set up
To harvest sunflowers effectively, conventional headers require some alterations. The following header attachments are strongly recommended:
Sunflower trays – are essential to retain heads and seeds in the header front. In modern headers with high comb lift heights, the use of a reel (preferably a bat reel) can stop some heads falling out the front.
Sullivan reel – works at the machine’s ground speed to help prevent blockages and reduce seed shattering.
Head snatcher (push bar under the cutter bar) – can speed up harvesting and reduce trash levels in the sample. This is not as important when using a rotary header and will not work if conditions are dry and stalks are brittle.
Use as slow a drum/rotor speed (~ 450 rpm for conventional headers and 250–350 rpm for rotaries) as possible without plugging of the drum/rotor. If this speed is too high, seed will be split in the separation area and excess trash will be produced. Check this setting by inspecting grain entering the sieve area.
Rotary headers should use large wire concaves and slotted grates. If the crop is over-ripe, use blanking sheets in the grate area to help reduce the amount of trash on the sieves as the threshing will all take place over the concave.
The drum/rotor must be set as wide as possible without allowing unthreshed grain to remain in the head. In most cases this setting is as wide as the harvester can go. Check the condition of the trash for over thrashed or unthreshed heads.
There are three basic adjustments required for the cleaning system:
The chaffer should be set at about 12 mm. Set the rear chaffer, if fitted, at 15 mm.
Begin with the shoe sieve set to 6–8 mm. For headers fitted with fixed perforated sieves, sieves of 10–12 mm are suitable. Check the contents and quantity of the repeats. If a high proportion of seed is present in the repeats, the shoe sieve needs to be opened. This is sometimes a very fine setting with a very slight change taking the sample from dirty to very clean, but the repeats are overloaded with good seed when the change is made.
Most headers require a fan speed of 800 rpm or greater. Fan settings need to have the chaff floating above the sieves and the grain not being thrown over the end. Set the fan speed as fast as practical without lifting seed over the sieve. A common fault in sunflower harvesting is to use insufficient air for fear of losing seeds over the chaffer.