Relationship between phosphorus concentration in soil solution and phosphorus in shoots of barley

Phosphorus concentration in the soil solution of agricultural soils should be a consensus of the agronomic and environmental aspect. Data from literary sources are inconsistent if the method of soil solution extraction from the soil and the method of phosphorus detection are not indicated. In the present paper a simplified procedure of soil solution extraction is used that is derived from the need of water to attain saturated soil paste. Based on barley cultivation in a plant growth chamber on 72 different soils the relationship between P concentration in simulated soil solution and the response of test plant (spring barley) was evaluated. Three approaches were used to derive an adequate P concentration in soil solution. Based on the diagnostics of P content in barley the following adequate P concentrations in soil solution were derived: 0.23–0.86 ppm P for colorimetry and 0.9–1.75 ppm P for ICP-AES. Using the concept of the boundary line of yield the critical P concentration in soil solutions was 0.8 ppm P for colorimetry and 1.3 ppm P for ICP-AES. The concept of the boundary line of P efficiency index enabled to define P concentrations in soil solution that can be considered as the lower limits of suitability from the agronomic aspect: 0.15 ppm P in simulated soil solution for colorimetry and 0.7 ppm P for ICP-AES.