Evaluation of drainage and tillage effect on watertable depth and maize yield in wet inland valleys in southwestern Nigeria

A study was conducted in three wet inland valley bottoms, namely, high (MHW), medium (MMW) and low (MLW) watertable sites to evaluate the effect of drained (D) and control (Do), and mound-tillage (MT), ridge-tillage (RT) and no-tillage (NT) treatments on watertable depth and yield of maize in 1990 wet and 1990/1991 dry season in southwestern Nigeria. The watertable depth averaged 30.0 cm in the drained plot and <15.0 cm in the control plot in 1990. The watertable tended toward its lowest depth averaging 44.8 cm in the drained and 26.2 cm in the control plot in 1990/1991. Soil moisture content was lower (P<0.01) and air-filled porosity greater (P<0.01) in the mound-tilled compared with the ridge tilled and no-till soils in both drained and control plots in 1990 and 1990/1991. Equally, green maize yield from the mound-tillage and ditch drainage system was greater (P<0.01) than the ridge-tillage and no-tillage systems in both seasons. Maize may be grown successfully with a ditch drainage and mound-tillage system in the wet soils in inland valley bottoms regardless of their watertable regimes in southwestern Nigeria.