The 2011 ASHS Annual Conference

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.  Nitrogen (N) -efficient cultivars of sweet corn show a biphasic yield response to nitrogen fertilization (initial yield increase, followed by no response beyond a moderate amount of fertilization), whereas N-inefficient varieties show a quadratic response to nitrogen.  We measured fresh kernel cut weight (t ha^-1) and percent usable ears for corn on the cob freezing (%COC) to determine interactions among two sweet corn varieties [‘Magnum II’ (N-efficient) and ‘GSS 1477’ (N-inefficient)], 6 N rates (0 to 225 kg ha^-1), planting date (May or June), and planting density (54, 62, or 69 thousand plants per ha).  We found ‘GSS 1477’ treatment interactions to be higher order than ‘Magnum II’.  Response to N was similar for % COC ears and fresh kernel cut weight.  Interplant competition for N was greater for ‘Magnum II’.  Record June rainfall in 2010 may explain why increased interplant competition reduced %COC in ‘Magnum II’ in the June planting but not in the May planting, and why at lower planting density and moderate N, May-planted ‘GSS 1477’ yielded greater fresh cut weight compared to the June planting.  Leaf chlorophyll at the 8-10 leaf collar stage predicted fresh cut yield, but the prediction was different for May- and June-planted sweet corn.