The Correlation of a Phosphorus Soil Test with the Response of Wheat Through a Modified Mitscherlich Equation

Variations in soil, season, and variety were found not to change the relative response of wheat to a soluble phosphate. But the difference in distribution pattern between the applied and native sorbed phosphorus varied their efficiencies such that the response to the applied phosphorus followed a c log x form of the Mitscherlich equation. Values of c for log x and c 1 for b 1 were established. When easily acid‐soluble forms are absent these constants can, through soil tests, be used to calculate approximate fertilizer needs and percentage responses obtainable with wheat for a broadcast and double‐disced application of soluble phosphate. The results obtained are in agreement with the writer's nutrient mobility concept.