| Abstract: | Calculation of labile phosphate from phosphate buffer curves A procedure to calculate labile P from phosphate buffer curves (Q/I curves) is presented. It treats the buffer curves as Langmuir adsorption isotherms and calculates the labile P by extrapolation to zero. In a long term P fertilizer trial the labile P calculated in this way was nearly equal to the increase in plant available P as extracted by calcium lactate. From a heavily fertilized vineyard soil, on the other hand, more P was extracted by 3 · 10?3 M CaCl2 during the first extractions than calculated from the buffer curves whereas on further extractions the two quantities approached each other. |
