Soil Solution Nutrient Concentrations Sampled with Tension and Zero‐Tension Lysimeters: Report of Discrepancies

Abstract

AbstractLysimeters were used to sample soil solutions in an ecosystem‐level study of nutrient cycling in a southern Appalachian deciduous forest watershed. Four lysimeters were installed at each of 16 randomly designated locations. At each location, first at the litter‐soil interface and again 30 cm beneath the litter‐soil interface, one tension and one zero‐tension lysimeter were installed side by side. Samples for 13 time intervals over a 15‐month period were analyzed for water volume, H+, NH+4, K+, Na2+, Ca2+, Mg2+, NO‐3, Cl‐, SO2‐4, H2PO4‐, and dissolved silica. The sums of cations, the sums of anions, and the anion deficit (unmeasured anions) were calculated for each collection. Estimates of soil solution composition and water flow differed according to lysimeter type. At the litter‐soil interface the zero‐tension lysimeters collected 7 times more water flow which had significantly higher concentrations of H+, Ca2+, and SO2‐ and significantly lower concentrations of Na+, K+, and Cl‐ than collections from tension lysimeters. At a soil depth of 30 cm, zero‐tension lysimeters collected 2.1 times less water which had significantly higher concentrations of NH+4, K+, NO‐3, Cl‐, SO2‐4, sums of cations, and sums of anions but significantly less silica than collections from tension lysimeters. A testable hypothesis is advanced to account for these observed discrepancies.