Critical limit of available phosphorus in soil for wheat crop by Olsen's method is

The critical limit of available phosphorus in soil for the wheat crop by Olsen's method is 10 kg/ha.
Olsen’s method is done for the estimation of phosphorus and is based on the extraction of phosphate from the soil by 0.5 N sodium bicarbonate solution adjusted to pH 8.5. this procedure is suitable for calcareous, alkaline, neutral, and slightly acidic soils containing CaPO₄.