|SCHARF, PETER - University Of Missouri|
|Sudduth, Kenneth - Ken|
|LORY, JOHN - University Of Missouri|
|STEVENS, GENE - University Of Missouri|
|OLIVEIRA, LUCIANE - University Of Missouri|
|SHANNON, MIKE - University Of Missouri|
|PALM, HARLAN - University Of Missouri|
|DAVIS, GLENN - University Of Missouri|
|DUNN, DAVID - University Of Missouri|
Submitted to: World Congress of Soil Science
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2010
Publication Date: 8/1/2010
Citation: Scharf, P., Kitchen, N.R., Sudduth, K.A., Lory, J., Stevens, G.W., Oliveira, L., Shannon, M., Palm, H., Davis, G.J., Vories, E.D., Dunn, D. 2010. Precision Nitrogen Fertilizer Management of Maize and Cotton Using Crop Sensors. In: Proceedings of the 19th World Congress of Soil Science, August 1- 6, 2010, Brisbane, Australia. p.29-32.
Technical Abstract: Nitrogen fertilizer greatly increases crop yields but requires large amounts of energy to produce and has undesirable off-site effects when it escapes from agricultural systems. Precisely matching N fertilizer rates to crop needs maximizes benefits while reducing negative impacts. Soil N supply to crops is spatially variable, so spatial diagnosis is needed to apply optimal N rates. Crop reflectance sensors provide an accurate and spatially-intensive method for diagnosing and applying the correct N rate. We have developed calibrations relating optimal N rate to reflectance ratios for maize and cotton. These calibrations require that sensor reflectance measurements be expressed as a ratio with measurements from high-N areas that are matched in growth stage, genetics, and environment. We have used these calibrations in demonstrating sensor-guided N applications to maize and cotton producers. Side-by-side replicated comparisons of sensor-based variable-rate N and producer-chosen N rates for 53 maize fields resulted in N savings of 16 kg N/ha and a yield increase of 110 kg grain/ha. Results from our first four demonstrations in cotton fields should be available by the time of the congress. Drift of sensors during the course of a day has been an unexpected obstacle and requires frequent re-measurement of the high-N reference area.