Farmers are given quotas as to how much grain they can sell. When the quotas are open to do so the farmer must somehow transport the grain to the elevators. Many hire large trucks to move the grain as the smaller farm trucks just aren't big enough to make the long trip that may be necessary worthwhile. Now that the grain elevators are far and few between this is often true. I took this photo of a line-up of grain trucks at a wooden grain elevator this past September (2006).