AbstractDetailed measurements were made of the distributions of roots, water, nitrate, potassium and magnesium in the soil beneath summer cabbage that had been grown in the field for various periods of time. With few exceptions the concentration of water and nutrients did not vary with horizontal distance; the only detectable trends were in the concentrations of nitrate and potassium in the surface layer beneath large plants but these trends were much less than those of rooting density. The vertical distributions of nitrate and potassium ions were largely determined by rainfall which resulted in much loss of nitrate from the root zone and movement of potassium down the profile. Removal of water by evapotranspiration was more or less uniform down the profile despite rooting density declining sharply with depth. The significance of these findings to computer simulation of water and nutrient uptake by plants is discussed.