The yield and phosphorus uptake of grasses and clovers from Welsh soils were studied in 6‐inch flower pots. Attempts were made to relate the phosphorus that the plants had been able to absorb to various measurements of the labile phosphorus in the soil. It is shown that in these‘phosphate fixing’ soils, absorption is not related to the exchangeable phosphorus as measured by equilibration. The values obtained for the latter are very high compared with the small amounts of phosphorus that the plants have been able to absorb, giving support to the view that the conversion of phosphorus to insoluble forms is not the main feature of‘fixation’ in these soils. Absorption of phosphorus by the grass was, however, related to the Larsen (L) values. In previously unfertilized soils, the fact that the L values were also related to the acetic‐soluble phosphorus content confirmed the belief that acetic extraction is a suitable means for assessing the abilities of such soils to provide the necessary phosphorus for plant growth. In soils containing reserves of residual phosphorus, however, much of the phosphorus that contributed to the L values was not extracted by acetic acid, and this method of extraction is unsuitable for use with such soils. Placement of the applied phosphorus near the root zone led to a decrease