An equilibrium tension lysimeter for measuring drainage through soil

An equilibrium tension lysimeter (ETL) was designed to maintain equilibrium between lysimeter suction and soil matric potential. Equilibrium tension l ysimeter replicates were installed in a natural prairie, and N-fertilized n o-tillage and chisel-plow agroecosystems to measure drainage through undist urbed soil. The ETLs were used to monitor drainage continuously at 1.4 m be low the soil surface through a 0.2-mu m pore diameter stainless steel porou s plate (0.19 m(2)). Heat dissipation sensors were used to record variation s in matric potential inside and outside the ETL's sampling area. Suction w as maintained, on lysimeters according to the matric potential experienced by the surrounding bulb soil (Cumulative lysimeter drainage was 199, 563, a nd 793 mm for the prairie, fertilized no-tillage, and fertilized chisel-plo w agroecosystems for 132 wk between 25 June 1995 and 3 Jan. 1998. Drainage accounted for 11, 31, and 44% of precipitation inputs for the prairie, fert ilized no-tillage, and fertilized chisel plow systems. Variability between lysimeter replicates was smallest for the prairie, where the coefficient of variation (CV) was 8.2%, and largest for the N-fertilized no-tillage agroe cosystem (CV = 36.6%).