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Fig. 5. Cumulative rainfall as a result of a storm on 11 July 1993 and rate of percolate accumulation in a recording pan lysimeter installed 50 cm below the soil surface
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sample bottle and another tube was routed from the bottle to the soil surface. Afterwards, the pit was refilled and a hand-held vacuum pump was used to remove any accumulated water from the bottle after
each rainfall. Fifty earthworm burrows adjacent to a long-term, no-till watershed (WS 191) were instrumented in this manner and flow was monitored from June to October 1987 (Edwards et al., 1989). The results indicated conclusively that the earthworm burrows functioned as preferential flow paths with the monitored burrows collecting up to 10% of the rainfall from individual storms and an average of 13 times more water than expected based on the diameter of their openings. The number of burrows that produced percolate and the amount of flow were a function of storm characteristics. High intensity rainfalls and dry soil surface conditions fostered flow in the monitored burrows, but low intensity storms did not yield percolate. The number of burrows that produced percolate and the volume per burrow increased with rainfall amount, whereas the percentage of rainfall captured by the burrows decreased. The results of a laboratory study supported these findings. When 30 mm of simulated rain was applied at a range of intensities to undisturbed soil blocks obtained from a no-till field, percolation began sooner and both percolate volume and the area of soil yielding percolate at the base of the blocks increased with rainfall intensity (Edwards et al., 1992).