Summary In a well‐structured soil at or close to pedal saturation, rainfall intensity in excess of pedal K sat is predicted to result in by‐passing flow through well connected structural voids. The depth of solute penetration (tracer dye and nitrate) under by‐passing flow has been predicted by D f =( P‐C p )/θ f , where D f is the depth of penetration of the leading edge of solute in by‐passing flow, P is gross precipitation, C p is the input volume transmitted through the soil peds and θ f is the operational volumetric moisture content in by‐passing. The timing of surface applied nitrate arrival at a channel bank is demonstrated to be related to by‐passing flow rather than uniform displacement. The relationship between nitrate load in soil drainage waters ( Y , mg s ‐1 ) and water discharge ( X , dm 3 s −1 ) was Y ∼ 6X after nitrate fertilizer application but subsequently declined to Y 0. 5X It is deduced that the decline resulted from inefficient leaching under by‐passing conditions once surface applied nitrate had become relocated within the soil peds.
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Smettem et al. (1983) studied this question.