Economics of phosphorus fertilization of barley as influenced by concentration of extractable phosphorus in soil

Field experiments were conducted at 60 sites in central and north-central Alberta to determine the yield response of barley (Hordeum vulgare L.) to phosphorus (P) fertilizer and economics of P application on soils with different concentrations of extractable P in the 0-15 cm soil layer. On the unfertilized plots, barley yield increased with increasing concentration of extractable P in the soil up to 22 mg P kg(-1), but the yield response to applied P decreased. The net present value (NPV) of returns from P fertilization increased with increasing rate of P up to approximately 51 kg P2O5 ha(-1). The NPV of applied P decreased with increasing concentration of extractable P in soil. On soils with extractable P more than 22 mg P kg(-1), P application did not result in positive NPV.