So it's not generally necessary to require a falling number test if you know what the protein content is. 6 Basic U.S. Classes of Wheat Wheat is the principal U.S. cereal grain for export and domestic consumption. In terms of value, wheat is the fourth leading U.S. field crop and our leading export crop. Wheat has two distinct growing seasons. Winter wheat, which normally accounts for 70 to 80 percent of U.S. production, is sown in the fall and harvested in the spring or summer.
Spring wheat is planted in the spring and harvested in late summer or early fall.
Where each class of wheat is grown depends largely upon rainfall, temperature, soil conditions and tradition. Generally speaking, wheat is more often grown in arid regions where soil quality is poor. Wheat classes are determined not only by the time of year they are planted and harvested, but also by their hardness, color and the shape of their kernels. Each class of wheat has its own similar family characteristics, especially as related to milling and baking or other food use. The dominant class in U.S. exports and the largest class produced each year.