Corn shows large responses to nitrogen (N) fertilizer application, depending on weather, soil characteristics, water
supply, crop uniformity and the nutrient responses of the cultivated varieties (Nagy, 1997). However, concerns
about N pollution of the environment, such as leaching of nitrates into ground water, nitrous oxide emission into
the atmosphere and other forms of environmental degradation have stimulated interest in low-input strategies for N
fertilization (Weisler et al., 2001; Sheng-wei et al., 2009).