Monday, 7 November 2005
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This presentation is part of: Nitrogen Management in Corn Production

Nitrogen Fertilizer Response of Individual Maize Plants as Affected by Day of Emergence.

Paul J. Hodgen, Fernando Solari, James Schepers, Richard Ferguson, John Shanahan, and Dennis Francis.

Recently developed crop canopy sensors are being evaluated for use in guiding variable rate applications of nitrogen (N) using ground-based equipment. These sensors output real-time information at 10 times a second, providing a sampling spatial resolution of approximately 22 cm for a ground based applicator traveling at 8 km hr-1.  This would allow for monitoring and fertilizing individual maize plants within a row.  The purpose of this study was to determine the responsiveness of individual (dominant and dominated) maize plants to commercial N fertilizer.  Plots were prepared by conventional tillage, seeded in four rows spaced 76 cm and 4.6 m long, achieving a plant density of 63,400 plants ha-1. Nearly 1,500 plants were marked with a plastic stake on their day of emergence (DOE), with all plants emerging 5 to 12 days after planting.  Nitrogen treatments were applied either 41 (V8) or 65 (VT) days after planting.  Treatments consisted of 3 or 6 ml of 28 % UAN solution plant-1, depending on their status of dominant (DOE 5-7) or dominated (DOE 8-12).  These treatments were compared to flat rates of 150 kg N ha-1 at v8 and VT and a zero N treatment.  Plant heights measured 32 days after planting (V5) were found to be significantly different (P<0.05) by 2 DOE.  Responsiveness to nitrogen fertilizer increased with each day of delayed emergence while yield levels obtained in g plant-1 declined with each day of delayed.  DOE had a greater impact on g plant-1 than distance to nearest neighboring plants.  These data clearly demonstrate that late emerging plants are very responsive and greatly inefficient with nitrogen that is applied mid-season. Furthermore the achievable yield per plant is greatly reduced by delayed emergence. Recognizing these inefficient plants will help to greatly increase nitrogen use efficiency in maize systems.


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