References
Black C.A. 1957. Soil Plant Relationships. John Wiley and Sons, Inc., NY.
Buckman, H. L., Brady, N. C. 1960. The Nature and Properties of Soils. 6th Ed., The Macmillian Company, NY.
Ferguson, Richard. Krista DeGroot, Editor. Nutrient Management for Agronomic Crops in Nebraska, EC 01-155-S. 2000. University of Nebraska-Lincoln Extension Service.
Kilmer, V.S., S. Younts, and N. Brady, Editors, The Role of Potassium in Agriculture. 1968. American Society of Agronomy, Madison, WI.
Penas, Ed, 1989 Soil Science Research Report, Dept. of Agronomy, University of Nebraska-Lincoln.