POTENTIAL SOIL POTASSIUM SUPPLY CAPACITY AS RELATED TO WHEAT POTASSIUM DEMAND

We examined soil potassium (K) supply capacity as related to wheat res ponse to K fertilization, using a cation exchange membrane (CEM) buria l technique to measure potential K supply rate. A growth chamber exper iment was conducted to determine soil and plant response relationships . Canadian Prairie Spring wheat (Triticum aestivum 'Biggar') was grown on three soils of different initial K fertility with three rates of a dded K. Wheat response to K fertilization was well related to the amou nt of exchangeable K and K supply rate in the soil. Soils with high in itial K supply rate demonstrated an adequate K release rate which was associated with low response to added K fertilizer. A soil K supply ra te less than 5 mu g cm(2) hr(-1) represented soil K supply power that is less than optimal for wheat nutrition.