Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2005
Publication Date: 11/1/2550
Citation: Hodgen, P., Solari, F., Schepers, J.S., Ferguson, R., Shanahan, J.F., Francis, D.D. 2550. Nitrogen fertilizer response of individual maize plants as affected by day of emergency. Agronomy Abstracts. Interpretive Summary:
Technical Abstract: 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.