The effect of lime admixture to trench backfill on the functioning of tile drainage in heavy soils

Abstract

The Kalnujai site was drained by a composite subsurface drainage system, with drain spacing 16 and 24 m, drainage trenches backfilled with clay loam mixed with 0.6% CaO. The effect of drainage installation variants was evaluated on the basis of drain discharge and watertable depth in the main drainage season (January to April inclusive) in the period of 2000 to 2002. The peak drainage discharge measured in snow melt period was 6.7 mm d-1, i.e. was 1.3 times higher than the design discharge (5.2 mm d-1) determined for a subsurface drainage according to soil texture and meteorological conditions. However, the differences of drainage discharge between the different treatments were insignificant. Lime amendments significantly lowered the watertable (0.21-0.25 m) and increased the surface water infiltration rate 1.5 times. Wider drain spacing from 16 to 24 m had no effect on water levels between drains and draining conditions in the area.