Most types of soybean plants produce mature beans in 7 to 10 days. The beans are ready to be harvested when they are plump and green. When the rest of the plant begins turning yellow, the beans are still edible but past their prime. If the beans themselves begin to turn yellow, they should no longer be harvested for human consumption.
Threshing is the process of separating the beans from their encasements. Today, most soybeans are harvested and threshed at the same time through the use of a combine. Combines must be carefully designed to separate the beans from the pods without breaking the beans. Breakage can lead to insect infestation, plant disease and general reduction of bean quality.
The last step of the harvesting process is the drying of the beans. This process lowers the moisture content of the beans, which allows them to be stored or processed for a longer amount of time. In warm climates, beans are spread out on a drying floor for several weeks so that the sun and air dry them naturally. In wetter climates, special machines called dryers push warm air over the beans to lower their moisture content.