Harvesting, Grading, and Storing

3.1 Harvesting of Soybean

Depending on the variety, soybeans can be harvested between 100 and 150 days after planting. If a farmer harvests before the crop is mature, it can mold and eventually rot due high moisture presence; the quality will thus be low. When soybeans are fully mature their leaves will turn yellow then brown and fall to the ground. Harvest when 90-100% of pods are brown and dry, but before they are brittle and shatter. Some soybean varieties will shatter when they are ready for harvest­ing while others do not shatter. Shattering may reduce grain quality and quantity if soybean is harvested late. Timely harvesting helps maintain seed quality and avoids infestation by insects.

Harvesting should be done in the morning hours when tempera­tures are low to avoid shattering. Do not harvest on a rainy day. Wait for the rains to stop to avoid drying problems which can lead to some losses.

During harvesting, cut the mature plants just above ground level. Do not mix variet­ies when harvesting especially when heaping the crop. It is recommended not to pull the plants out by the roots. The roots of soybean plants have nodules of nitrogen fixing bac­teria, which may help establish a colony of these bacteria in your soil to aid future planting.

3.2 Post-harvest Operations for Soybean Grain

Post-harvest options are generally all the activities that can be carried out after the harvesting of crops in order to convert it to use by man and animal. It can be classified into primary and secondary pro­cessing. Primary processing includes threshing, winnowing, cleaning, separation, grading, sort­ing, packaging, transportation, marketing, storage and so on whilst secondary crop processing in­volves processing of food for direct consumption.

3.2.1 Threshing Soybean

Thresh manually or mechanically when the plants are properly dry and as soon as possible. Manual threshing is mainly recommended for small-scale production. It involves piling soybean plants on tar­paulin or putting dry soybean pods in sacks and beating them with a stick. Beating the plants should be gentle to avoid destroying the embryo which eventually may affect germination and overall seed quality. The soybean plants can then be winnowed to remove the grain from the soybean debris.

3.2.2 Grading

The purpose of grading is to ensure that discoloured grain, diseased grain, cracked, in­sect-damaged, shrivelled, any debris and foreign matters are removed. This attracts buy­ers and fetches premium prices on the market.

3.2.3 Storage

Seed storage becomes necessary if the processed seeds cannot be sold immediately or when there are surplus seeds carried over to the next season. The conditions under which the grains are stored greatly influence the quality of the processed product. At harvest, the grains usually contain about 14% moisture. However, soybean should be stored at a mois­ture content of less than 10%. A soybean seed is sufficiently dry when it cannot be dented with the teeth or fingernails. High moisture content in stored soybean encourages the de­velopment of various agents of deterioration, such as insects and microorganisms. Good storage management can greatly influence the storability of soybean and subsequent germination when planted in the field. Do not leave soybean exposed to high temperatures to avoid seed quality deterioration.