In the following picture you can see green beans...
and in this picture, are soybeans...
Why Aren't Soybeans Harvested When They Are Green?
If you or I waited to harvest the produce from our garden when the plants were dead, like we do with our field crops, there probably wouldn't be anything left to produce. Sure, it would probably be there, but the quality wouldn't. When you plant a garden, you aren't actually growing grain like we are. While they appear to be dead, they are actually ripe!
Grain crops such as corn and soybeans are harvested when they are ripened which means their green tissue has turned brown, or dried down as we call it. Crops have a long storage life, so they have to be dry so they don't get moldy. No one likes moldy food, just like animals don't like moldy food if the crops are being used for animal feed.
Another reason that we let the plants dry down naturally is because if the grain is hauled into a grain elevator, to be shipped elsewhere and made into certain foods or other things, it needs to be at or below a certain moisture, so that it can be stored for long periods without going bad. The moisture for soybeans needs to be at or below 13%. If it is above that percentage we are docked in the price.
Here you can see the soybeans coming out of the grain cart auger.
We are able to dry our grain, specifically our corn. Most of the time we let Mother Nature handle the soybeans and they are able to be hauled straight to the elevator. If they are too wet, we put them in a grain bin with a large fan to help dry them out before they are hauled to the elevator. It's a little more difficult to get corn to dry down enough to haul straight to the elevator from the field, so we use our grain dryer most of the time for corn.
The grain dryer system is another post in itself, so I will have to fill you in on that at another time;)+