Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2005
Publication Date: 9/27/2005
Citation: Roberts, D.F., Kitchen, N.R., Scharf, P.C., Sudduth, K.A. 2005. Environmental implications of sensor-based variable-rate n application in corn [abstract] [CDROM]. ASA-CSSA-SSSA Annual Meeting Abstracts.
Technical Abstract: Active-light reflectance sensors have been shown to be an effective tool in assessing site-specific N need for variable-rate fertilizer applications in wheat. Several research groups, including ours, are investigating this same technology for variable-rate N fertilization in corn. This 2004 study was conducted in Missouri on seven producer corn fields to compare soil and crop N measurements from a treatment using reflectance sensors (i.e. a variable-rate N application) to a treatment of uniform N rate application. Measurements included economic optimal N rate (EONR), crop N yield use efficiency (YUE), N fertilizer recovery efficiency, and post-harvest soil nitrate measurements. Averaged over all fields, the sensor-based method reduced N fertilizer rate by 37 kg/ha. As N rate increased and approached EONR, YUE decreased for each of the seven fields. Yet within a field, EONR and YUE were spatially variable. Compared to conventional single-rate application, sensor-based application did reduce post-harvest soil nitrate for some sub-field areas with little or no reduction in yield. 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.