Effects of Envelope Materials and Drain Holes Spacing on Sub-Surface Drainage System in Akure, Nigeria

Abstract. Hydraulic effects of different three envelope materials (wood shavings, coconut fibre, 6.5 mm diameter of crushed stones) and drain spacing on sub-surface drainage systems in Akure Nigeria were determined. Nine (9) Polyvinchloride (PVC) drain pipes of uniform lengths 3m and diameters 10 cm each were used while three lines of drain holes with spacing of 15 cm, 30 cm and 45 cm respectively were drilled on the pipes and were installed across 2% slope at 60 cm depth. Each of the three selected envelope materials were used on the three drain pipes with different drain holes spacing. After each irrigation session, volume of drained water and duration were measured. Results showed that crushed stone, coconut fibre and wood shaving had maximum average drain outflows of 3.64 liters, 2.88 liters and 2.44 liters respectively at drain spacing of 15 cm. Similarly, maximum drain outflow rates of 0.10 liters/min (crushed stone), 0.06 liters/min (coconut fibre) and 0.04 liters/min (wood shavings) at drain spacing of 45 cm each. Drainage duration was longest with wood shavings as envelope material at drain spacing of 15 cm in all the materials and drain spacing considered. Positive correlation (P>0.01) existed between the envelope materials and drain holes spacing considered. Soil classification was sandy clay loam, 57.55% sand, 18.85% silt and 23.60% clay while moisture content, bulk density and specific gravity were 17% (dry basis), 1.43g/cm 3 and 2.57. Using crushed stone as envelope material at drain spacing of 15 cm was the most effective in field drainage systems.