ABSTRACT
The United States is the world’s largest producer, exporter, and importer of nitrogen (N) fertilizer. Oklahoma lies in the West South Central Region which includes Texas, Arkansas, and Louisiana. The Southern Great Plains comprises approximately 75 percent of the State of Oklahoma and only excludes the Coastal Plains and the Ozark and Quachita Highlands. N is the fertilizer nutrient needed in the largest quantity for crop production in Oklahoma. N fertilizer is used mainly for production of wheat, cotton, grain sorghum, corn, bermuda grass, and other nonlegume hay forages. The use of nitrification inhibitors in more humid areas of the United States, and in areas under irrigation, has had some success in improving N utilization by the crop. Efficient use of N in agricultural production systems can be viewed from agronomic, economic, and environmental perspectives. The method of fertilizer placement may offer some advantages in increasing yield and N uptake in the crop.
