THE PHYSICAL FEATURES and the climate of Oklahoma permit a great diversity of agricultural interests and products. The wide range in elevation, increasing from the southeast to the northwest, and the mean annual temperature, which is much higher in the southeast than in the northwest, make possible the production of widely different crops. The rainfall, which decreases to a marked degree from east to west, affects agricultural production, as does the wide variation of soils.
The physiographic regions are usually divided by sharp boundaries, though they sometimes shade easily from one to another. Generally the state is divided into mountainous or hilly areas--the Ozark Mountains in the northeastern part of the state; the Ouachita, or Kiamichi, Mountains in the southeastern; the Arbuckle Mountains in the south-central; and the Wichita Mountains in the southwestern portion. The plains or valley regions are separated into seven divisions--the Red River area south of the Arbuckle and Kiamichi mountains; the Lower Arkansas Valley between the Ozark and Kiamichi mountains; the Sandstone Hills, which lie west of the lower Arkansas Valley; the Prairie Plains, which lie west of the Ozark Mountains; the Redbeds Plains, which comprise a wide strip extending north and south through the central part of the state; the Gypsum Hills west of the Redbeds Plains; and the High Plains in the northwestern part of the state. These various regions, together with other factors, make the state an area of diversified interests with respect to crops and pasturage.