Use of time domain reflectometry (TDR) methods may help researchers better understand how solutes are transferred from soil to surface runoff, affecting solute concentrations and losses. A laboratory experiment with rainfall simulation was conducted to study the effects of phosphorus (P) application rate and soil surface cover condition. An analysis of relationships between bulk electrical conductivity (EC[Subscript b]) in a thin top layer of soil measured by TDR and the solute concentrations in runoff water was performed. The results indicated that EC[Subscript b] in the top soil layer (mixing zone) was linearly related to both total dissolved solids (TDS) and orthophosphate phosphorus (PO4-P) concentrations in surface runoff when the soil received monobasic amonium phosphate (MAP) at rates of 125, 300, and 600 ppm (the relationships were not statistically significant for the 0 and 50 ppm added P treatments); EC[Subscript b] and P04-P or TDS versus time was best expressed as a power function. Added P significantly increased the EC[Subscript b] in the top layer of soil as well as ,TDS and P04-P concentrations in surface runoff. Whether the soil pans did or did not have a screen cover did not effect EC[Subscript b] in top soil layer or TDS Or P04-P concentrations in runoff water, but because a screen cover decreased the volume of surface runoff and increased the volume of subsurface drainage, the losses of TDS and P04-P in the surface runoff and subsurface drainage are significantly affected.