SUNFLOWER POST HARVEST

Farmers commonly leave sunflower in the field until the plant is completely dead and seed is thoroughly dried. Heads are then cut off immediately and threshed in the field. Often plants ripen at different times so the crop is left in the field for an extended period until all heads have dried out. This means that much seed is lost due to birds and also heads shattering with seed falling to the ground.

To reduce these losses and to encourage rapid drying plants should be harvested as soon as the backs of heads turn from green to yellow and the bracts around the edge of heads turn brown. For a crop that ripens unevenly this means harvesting has to be done in stages. Plants can be cut and stocked or each head can be pinned upside down on its own stem. Alternatively, heads can be taken to a store and put out in the sun each day to dry. If this is done heads should not be piled on top of each other or they will rot.

After thorough drying the heads are threshed by beating with sticks on mats or clean floor. The seed should then be winnowed to remove debris and poorly filled seeds.

If sunflower seeds are stored   with a high moisture content they may be attacked by moulds which may result in seed containing the poison aflatoxin. For safe storage seed should be dried for two days in the sun after threshing. The moisture content of stored seed should be less than 9.5 percent.

Aflatoxin.=is very toxic substance formed by fungus Asperigillus flavus which  grows on seeds and nuts