Within-field variation in corn yield and grain quality responses to nitrogen fertilization and hybrid selection

This study was conducted in Paris, IL, from 2001 to 2003 involving three corn (Zea mays L.) hybrids, five N rates (0, 112, 168, 224, and 336 kg ha-), and six site-year comparisons to determine the significance of within-field variation in corn yield and quality responses to N fertilization, differences between hybrids in yield and quality, and the feasibility of within-field variable hybrid selection. On average, N fertilization significantly increased corn yield, protein content, and test weight, but decreased corn oil and starch content. The overall economically optimum nitrogen rate (EONR) was 125 kg ha(-1), but EONR varied from 93 to 195 kg ha(-1) in different environments. The N rates that would maximize protein content and test weight (MAXN) varied from 143 to 303 kg ha(-1) and 0 to 235 kg ha(-1) in different environments, respectively. Significant within-field variability in N response was detected in five of six environments for yield, but not in more than two environments for any quality parameter. Hybrid differences were significant in all six environments for test weight, followed by oil content (five), protein and starch content (four), and yield (three). Hybrid differences between 33G26 and 33J24 in test weight response to N were consistent across environments, showing the potential of hybrid-specific N management for this quality parameter. However, hybrid differences in yield and quality did not vary significantly over space in most environments, showing limited potential of within-field variable hybrid selection. Further studies involving more diverse within-field soil-landscape conditions and hybrids are needed.