Estimating P loss potencial by P Index

Phosphorus (P) is the limiting element of eutrophication. The P losses by runoff can affect water quality. The objective of this study was to estimate the P loss from soil to water through the P Index method with Brazilian experimental data and to compare this estimated data with the analytically determined soluble P, particulate P and total P. The P Index was developed in the United States of America, in 1993, and has been widely used in several versions. In this study, four P Index versions were analysed using experiments from southern Brazil. The estimated P Indices were compared with the P concentration and loss in runoff. Besides the correlation analysis, the stepwise regression was used to analyze the influence of different components of the PI in P concentration and loss in the water. The Original P Index version was more significant with P concentration in runoff. The regression analyses indicated that the soil erosion factor did not influence P loss from soil to water.