Marschner (1995) reported that root size is an important factor for nutrient acquisition such as P and K that are immobile in the soil. Crop yield is very important to farmers, Barber and Mackay (1986) found a positive correlation between yield and root size in maize hybrid B73 x Mo17. A strong relationship between the maize root growth and P uptake was reported by Maizlisch, et al., (1980); Barber and Mackay (1986). Root system architecture brings effective nutrient acquisition and bumper yield (Linkohr et al., 2002; Yan et al., 2004).