Subsurface drainage effect on soil and rice crop

C.S. Chan and A.W. Cheong

Abstract

Studies on subsurface drainage were carried out on sandy clay loam soil in MARDI, Seberang Perai Research Station from 1995 to 2000. Subsurface drains installed at a constant depth of 45 cm and variably spaced at 2, 4, 8, 16, and 28 m were tested to establish a relationship between soil bearing capacity and soil depths in the installed subsurface drainage systems. Additionally, soil bearing capacity at different soil depths in relation to the drain spacing were evaluated. Fluctuation of the water table levels due to the effect of subsurface drain spacing with reference to rainfall were also studied. Soil bearing capacity increases with soil depth which from 15 cm and beyond is strong enough to ably support the weight of a large combine harvester. Soil bearing capacity is higher at denser subsurface drainage intervals only when with normal rainfall, but not as indicative when at its extremes, being with too much or too little rain instantaneously. Rice yields from the off-season and main season between the subsurface systems were compared with conventional yieldselsewhere in the station. It has been shown that in the subsurface drainage plots the yield gap between the two seasons was insignificant, but with the recorded off-season average yield being slightly higher than the main season. Average yields obtained under subsurface drainage systems were however noticeably higher when compared with harvest from fields without such a drainage facility irrespective of the season.

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