Gu et al. (2011) investigated the root distribution of some rice cultivars under varied water and N conditions and found that the root growth and distribution could be optimized by adjusting N application and irrigation regime. Wang et al. (2011) repored that root vigor tended to be decreased by water stress to a higher extent in plants with low NUE compared with those with high NUE on root characteristics, N, and water use efficiency in maize.