Leachate Collection Efficiency of Zero‐tension Pan and Passive Capillary Fiberglass Wick Lysimeters

Abstract

Lysimeter leachate collection efficiencies (LCEs), which are the measured leachate volume divided by estimated percolation water, are needed to convert measured leachate volumes to actual leachate fluxes. In this study, LCE of zero‐tension pan and passive capillary fiberglass wick lysimeters were evaluated and directly compared. A total of 18 pan and 18 wick lysimeters were installed 1.2 m below the soil surface in tilled and no‐till plots. From May 1995 to April 2000 the lysimeter LCEs were evaluated using a water‐balance method with evapotranspiration (ET) estimated by the Penman‐Monteith equation. On average, wick lysimeters collected 2.7 times more leachate than did pan lysimeters, and tillage had no effect on the 5‐yr total leachate volume at the 5% significance level. If the anomalous 1997 leaching year with an exceptionally warm and wet winter was excluded, wick and pan lysimeters collected about 50 and 20% of precipitation, respectively, from both tillage systems. The average 4‐yr LCE for wick lysimeters was 101% and that for the pan lysimeters was 40%. The much higher LCEs for both pan and wick lysimeters during the 1997 leaching year were thought to be the result of over‐sampling of leachate during the exceptionally wet and warm winter. Errors of ET estimates associated with estimating crop residue cover and water stress adjustment parameters were small. Errors in LCE estimates can be mathematically shown to be in the same range as those of ET estimates.