Fig. 5. Plots of the percentage of soil redox (E_h) measurements (49 measurements made fortnightly between August 1992 and July 1994) to fall below 150 mV, the approximate redox potential at which Tc^VII is likely to be reduced to Tc^IV at soil pH values of between 6 and 8. The vertical lines represent water table depths in shallow and deep lysimeters (35 and 65 cm, respectively).