(i) Unisize rain (uniform drop sizes) was produced using the CSIRO Canberra rain tower, consisting of drop forming modules positioned 12.2 m above the soil surface and fitted with hypodermic needles spaced on a 25-mm grid.
s) for natural, unisize, and multisize rains (Table 2) were calculated in the following ways:
(ii) Drop impact frequencies for 2.6-mm drops (unisize rain) were measured under the Canberra rain tower and reported by P.H.
(iii) Drop impact frequencies for 2.3-mm drops (unisize rain) were calculated using intensity and drop diameter in the equation: [log.sub.10] volume = -0.09 + 0.40 D, where D is diameter (mm) and [R.sup.2] = 0.98 (B.
Unisize rain had consistently lower drop impact frequencies than either multisize or natural rain, particularly 2.6 mm drops (Table 2).
Nonetheless, at each intensity, raindrops impacted on each [cm.sup.2] of soil surface more frequently under intermittent rain than under 2.6 mm unisize drops and at the same rate as 2.3 mm unisize drops.
For the Sodosol there was a significant trend towards greater suction under seals formed by unisize rain (Table 5), particularly at lower rainfall intensities.