Nitrogen Use Efficiency in Processing Sweet Corn

Sweet corn (Zea mays L.) is a major processing crop in the upper Midwestern United States. Our objective was to update nitrogen recommendations using modern cultivars of sweet corn under multiple crop management strategies. We measured fresh kernel cut weight (t·ha^-1) and percent usable ears for corn on the cob freezing (%COC) from May and June plantings in 2010–12 to determine yield and nitrogen use efficiency (NUE) responses among two sweet corn cultivars (‘Magnum II’ and ‘GSS 1477’), 6 nitrogen fertilizer rates (0 to 225 kg ha^-1), and 3 planting densities (54, 62, or 69 thousand plants/ha). We define NUE as the ability to convert N fertilizer to harvested yield [kg yield (kg available N)]. Overall fresh kernel cut weight was higher in ‘GSS 1477’, but NUE fell more rapidly than in ‘Magnum II’ as N increased. The lowest planting density resulted in higher NUE than the highest planting density. Increased planting density reduced fresh kernel cut weight in ‘Magnum II’ but not in ‘GSS 1477’, and increased planting density reduced fresh kernel cut weight in every N treatment except 180 kg·ha^-1. A linear increase in %COC in response to added N was observed in ‘GSS 1477’, but the response in ‘Magnum II’ was quadratic. Low N rates reduced %COC more at high planting density than at low planting density. Variation in the response to N and population density among the six planting seasons studied (2 plantings per year, 3 years) was substantial and might be explained by temperature and rainfall patterns observed after planting and during kernel development.