Comparison of three methods for field measurement of solute leaching in a sandy soil

To identify the most suitable technique for measuring solute leaching in a sandy soil, we compared three methods in an irrigation experiment (irrigation rates: 5 and 2.4 mm h(-1)) using Cl- as a tracer. We tested tensiometer-controlled suction plates, wick samplers, and ion-exchange resin boxes installed between fiberglass pads. Ten samplers of each type were installed at a 52-cm depth (suction plates) or a 60-cm depth (wick and resin box samplers) into soil monoliths. The recovery of water and Cl- by the suction plates varied little with irrigation rate (107-118%). The wick samplers performed well during 5 nun h(-1) irrigation (Cl- recovery: 111%; water recovery: 103%). However, at the irrigation rate of 2.4 mm h(-1), the water recovery was significantly lower (70%), probably because the soil suction exceeded the maximum capillary force of the wicks. The wicks did not induce a retardation or additional dispersion of Cl- compared with suction plates. The recovery of Cl- by the resin boxes was only 6%. Tensiometer-controlled suction plates allowed an overall satisfactory estimation of water and solute fluxes in the sandy soil.