Harvesting Sunflowers

Harvesting Sunflowers

Sunflower is amongst the most highly profitable cash crops. Farmers are increasingly getting into sunflower farming. Sunflower provides farmers with the opportunity to reap high yields, even in arid areas. However, sunflower is highly susceptible to damage, especially by birds, and so tends to be only profitable to farmers who are familiar with or possess a certain amount of knowledge about sunflower harvesting.

Table of Contents

Harvesting Time (When to harvest sunflower)

Harvesting sunflower calls for an understanding of the exact time the crop reaches physiological maturity, which is basically when the maximum seed height has been reached. Sunflowers tend to reach physiological maturity before they are dry enough to be harvested. This is usually 120 to 160 days for most varieties and 90 to 120 days for short varieties, after the planting period. Note that sunflower can be harvested at any given time after reaching physiological maturity. Sunflower harvesting should ideally be carried out when the crop’s moisture content is at 9%. However, due to frequent attacks by birds, it can be harvested earlier and dried to reach the recommended moisture level. Harvesting sunflower with moisture content higher than 9% puts the crop at risk of mould in storage, hence the need for drying. Harvesting at very low moisture levels of less than 6% results in increased admixture as the stalks and heads become dry and brittle, easily shattering into small pieces.  Harvesting sunflower is done when the back of the heads turn yellow and the outer tracts are about 80% brown. The most ideal day time for sunflower harvesting is in the morning when temperatures are cool.

Harvesting methods (How to harvest sunflowers)

Sunflower harvesting often adopts mechanical means, particularly sunflower combine harvesters. The combines are used to perform several operations such as cutting the crop, separating the grain from the straw, cleaning the grain from chaff and transporting grains to the storage tank. Combines used for grain harvesting are also suitable for harvesting sunflower, provided proper machine settings and adjustments have been made. There are 3 types of combine headers often used for sunflower harvesting. These include row crop, corn, and small grain platform head.

  • Row Crop Heads: commonly used to harvest crops such as grain sorghum and soybeans. There usually no adjustment adjustments required. However, the downside is that a significant amount of stalk enters the threshing mechanism and must be removed from the seed by the cleaning shoe. Row crop heads are generally expensive to maintain.
  • Corn Head: When using con heads, it is essential to attach a stationary knife that would be able to effectively cut the stalks.
  • Small Grain Platform: When used without modifications, it can cause shatter loss and loss of whole heads. Attachments therefore need to be added. The attachments are designed to gather only the sunflower heads and eliminate as much stalk as possible. They consist of pans about 3 to 5 feet long extending in front of the cutterbar and a modified reel or deflector.

Note that sunflower harvesting machinery are continuously being developed to minimise yield losses. Although mechanical harvesting means are popular, some farmers still use manual methods. Manual harvesting is practiced by cutting the crop with a sickle or knife, at about 15cm stem height. Some farmers allow the seeds to fully ripen on the stem then cut the stem an inch below the head when seeds are beginning to loosen from the head. The downside of this method is that sunflower tends to be attacked by birds when left in the fields. Another method comprises of cutting 3 to 4 inches below the stem when approximately 2/3 of the seed matures. Afterwards, a plastic bag is wrapped around the heads in a well ventilated area where it is allowed to dry.

Drying (How to dry sunflower heads)

Sunflower harvesting is usually carried out soon after maturity when the moisture content is above 10% to protect the yield from birds. Drying is therefore necessary to reach the suitable 9% moisture content for storage. In fact, it has been proven that sunflower harvested at 10% moisture content has the same fate to that harvested at 15%, hence the need for drying. Mechanical sunflower drying methods are preferred over manual drying techniques. Hot air drying comprising of fixed batch, recirculating batch or continuous flow dryers are all suitable for reducing moisture content. Sunflower tends to dry faster than most grains and so caution should be taken not to over dry the seeds. The recommended air temperate is approximately 40oC to 50oC. For continuous flow dryers, temperatures in the plenum of the dryer ought to be close to 70oC.  Batch and bin dryers are operated with temperatures ranging between 43oC to 60oC. Excess heat causes nutmeats to be steam wrinkled or even scorched. Note that sunflower used for seeds should not be dried in plenum exceeding 43oC.  When drying sunflower using batch dryers, seeds should be moved to the cooling phase once the moisture content is at 10.5%. After cooling, the seeds are tested to ensure temperatures are at 9%. Note that this should be done by an experienced individual as drying often causes hazard fires. Manual methods of drying sunflower involve placing them in thin layers on open ground, occasionally turning the heads to ensure that it dries evenly and faster. When doing this, avoid staking them in a pile. It is important to ensure that there is ample air circulation to avoid rot.

Storage (How to store sunflower correctly)

Conditions of the storage facility are an important aspect of the sunflower harvesting process. Seeds placed in storage must have 9% moisture content in order for them to last for prolonged periods.  Seeds with 12% to 15% moisture content can only be stored temporarily, preferably in freezing storage conditions. Note that moisture content above 10% promotes spoilage. Aeration is essential for controlling grain temperatures. It is also used to control insect and fungi infestation during storage. Aeration can be achieved through the use of floor-mounted dusts or portable aerators. Farmers who do not have access to means of aeration are advised to rotate seeds between the bins. Make sure to leave an air space on top of the bin in order to monitor the condition of stored seeds. Under dry, clean, aerated conditions, sunflower can last more than one season. In fact, it has been proven that sunflower seeds remain viable for 12 months when stored under the right conditions for example in a dry cold room, refrigerator or freezer. However, processors of non-oilseed do not favour sunflower that is stored for over a one season.

Yield (Amount of yield produced)

Harvesting sunflowers with high moisture content normally results in higher yields, less bird damage and less head dropping and shattering. Note that this only applies when proper drying measures are taken. A productive sunflower yield is usually 1.2 to 1.8 tonnes per hectare under dry land. However, most farmers record lesser yields due to losses during the harvesting period. Improper handling of harvesting machinery and lack of sunflower management skills are often the reasons behind lower harvests.

Sunflower is highly susceptible to attacks by birds, therefore, delayed sunflower harvesting leads to yield loss. In addition, more yield tend to be lost when harvesting sunflower from the fields as well as when processing. As such, if farmers are to successfully partake in the lucrative business of growing sunflower, it is of the essence that they acquire the appropriate skills and knowhow. This can be attained through interaction with experienced farmers, attending relevant workshops and reading widely on sunflower harvesting techniques.