INFLUENCE OF TILLAGE PRACTICES AND NITROGEN FERTILIZER RATES ON ROOT-LENGTH DENSITY, ROOT DRY WEIGHT AND MAIZE GRAIN YIELD

Field studies on a Typic Haplustalf soil complex were conducted for three years during 1997 - 1999 in Nigeria on maize (Zea mays L.) yield. The effects of five tillage systems were assessed (viz, ridging with arara (an oxen-drawn, light-weight tool carrier,) ridger (TI), ridging with emcot (an oxen-drawn, heavy-weight tool carrier) ridger (T2,), mouldboard ploughing followed by disc harrowing and ,mouldboard ridging (T3), disc ploughing followed by disc harrowing and disc ridging (T4), and manual ridging (T5) as a control. A factorial experiment with five tillage practices as horizontal treatments, four nitrogen rates as vertical treatments, and two planting methods as sub-plot treatments in four replications were conducted over three years (1997 -1999). Results from this 3-year field study indicate that soil water content was only influenced by tillage treatments but not by other factors. The variation in volumetric soil water contents at seedling emergence, anthesis and physiological maturity with tillage treatments indicates that maize used different amount of soil water at these stages. The mean penetration resistance (1.4 MPa) at T4 plots was significantly lower than the mean penetration resistance of 3.5, 2.8, 2.6 and 2.9 MPa at T1, T2, T3 and T5 plots, respectively. Theinteractions of tillage treatment x nitrogen fertilizer rates significantly (PO≤0.05) affected the root-length density and root dry weight. Increase in N fertilizer rate (upto 120 kg ha-1) reduced root dry weight but increased root-length density of maize in 0-to 30-cum, soil layer