Submitted to: North Central Extension Industry Soil Fertility Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 21, 2009
Publication Date: November 18, 2009
Citation: Kitchen, N.R., Roberts, D.F., Sudduth, K.A., Drummond, S.T., Scharf, P.C. 2009. What are the Benefits of Canopy Sensing for Variable-Rate Nitrogen Corn Fertilization?. North Central Extension Industry Soil Fertility Conference Proceedings. 25:173-180. Technical Abstract: Canopy reflectance sensing for assessing crop nitrogen (N) health has been proposed as a technology on which to base top-dress variable-rate N application. The objective of this research in Missouri was to evaluate the economic and environmental benefit of active-light crop-canopy reflectance sensors for corn N rate decisions. A total of 16 field-scale experiments were conducted over four seasons (2004-2007) in three major soil areas. Multiple blocks of randomized N rate response plots traversed the length of the field. Each block consisted of 8 treatments from 0 to 210 lbs N/ac on 30 lbs N/ac increments, top-dressed between V7-V11 vegetative growth stages. Canopy sensor measurements were obtained from these blocks and adjacent N-rich reference strips. A sufficiency index calculated from the sensor readings correlated with optimal N rate, but only strongly in 50% of the fields. While soil type, fertilizer cost, and corn price all affected our analysis, a modest ($10 to $20/ac) profit using canopy sensing was found. Fertilizer savings of 10 to 40 lbs N/ac could be expected in many situations, but savings also varied by reflectance readings, soil type, and fertilizer and grain prices. These results affirm using crop-canopy reflectance sensors for detecting corn N fertilizer needs.