Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/10/2005
Publication Date: 9/10/2005
Citation: Kitchen, N.R., Sudduth, K.A. 2005. Real-time corn assessment for variable rate nitrogen management [abstract]. It's the Water Workshop.
Technical Abstract: The main goal of this project is to reduce nitrogen (N) loss from corn fields while maintaining full productivity levels. Applying more N than the crop can use results in unused soil nitrate-N and increased potential for N loss. Corn producers want to be good environmental stewards; however many of the ideas proposed for reducing N loss from corn fields create the risk of reduced productivity and profitability. Variable-rate N applications will be needed to minimize excess N fertilizer without reducing yields. Recently developed tools to help producers know the correct N rate to apply have generally not been very reliable or easy to use. However, advances in “active light”, reflectance-sensor technology have allowed researchers to explore a better system for assessing N needs and automatically adjusting N application rates. This system is based on the fact that corn that is needing N is lighter in color, usually smaller, and reflects light differently than corn that has enough N. Our goal in this project is to conduct variable N studies in such a manner that we can both gather information to improve the science of N management in corn and demonstrate the potential of this approach to farmers and agricultural service providers. In 2004, the project was conducted on seven producer fields in Missouri. Variable rate application based on the reflectance sensor approach applied 33 lbs N/acre less than the average of the producer conventional rate. For one location, N applied using the sensor was much less (about 100 lbs/acre) than the conventional rate, and this was the correct decision. This site had previously been managed as a pasture and was first put into crop production in 2003. We presume that this dramatic decrease in N with variable rate was because soil N mineralization following the pasture was much greater than what would be expected from farmland continuously managed in grain crops. Over all locations, the economic impact of variable rate application was about a $4.00/acre increase in return compared to the conventional rate. We recognize that $4.00/acre alone will not convince farmers to adopt this innovative method of N management in corn. Adoption will likely occur once profitability improves and environmental benefits are documented. Based on these preliminary results, the use of active-light reflectance sensors to control in-season corn N fertilization in the U.S. Midwest is promising.