The influence of different intensities of phosphorus fertilizing on available phosphorus contents in soils and uptake by plants

A gradual increase of phosphorus (P) concentrations in combination with organic and mineral fertilizers was applied to clayey soils at six precise experimental field sites with different climatic conditions within the Czech Republic. Soil samples were collected after the harvest of barley. Readily available P concentrations were determined using water and 0.01M CaCl2 extractions, mobile phosphate contents were determined using the extraction procedures Mehlich 3 and Olsen. Furthermore, P uptake by barley plants was assessed. All selected procedures showed that increasing concentrations of applied P increased the mobile and readily available P contents in soils. Phosphorus uptake by barley plants ranged between 9.00 and 14.5 kg/ha and increased P application resulted in increased P concentrations in plants. Statistical analyses were performed using the Spearman test. The closest relationship was obtained for P uptake by plants and the water extraction (r = 0.81). Significant relationships were also obtained for plant uptake and the Mehlich 3 and CaCl2 methods (r = 0.40 and 0.36, respectively). There was no statistical dependence between P uptake and the Olsen method (r = 0.25). Regression analysis was expressed best as linear regression. The closest relationship was found for water extracts and P uptake by plants (with a determination coefficient of 65%). Determination coefficients for P uptake and other methods used were significantly lower (max. 20%).