ARS | Publication request: What’s The Right Amount of N? Using Sensors May Provide Better Answers

Submitted to: Fluid Journal
Publication Type: Trade Journal
Publication Acceptance Date: January 15, 2008
Publication Date: March 1, 2008
Citation: Kitchen, N.R. 2008. What’s The Right Amount of N? Using Sensors May Provide Better Answers. Fluid Journal. 16(2):60.

Technical Abstract: Environmental and, more recently, economic pressure on nitrogen (N) applications in corn production systems has prompted new research to find alternative methods of N fertilizer use efficiency. Traditional soil sampling and yield goal methods for N fertilization typically result in only about 30 to 40% of N applied being removed with the grain. A new innovative approach is to use the color and biomass of the growing crop as a “bioassay” of what N fertilizer is needed. This can be accomplished using reflectance measurements obtained by optical sensors. A real advantage of this approach is that these sensors can attached to field equipment so that the N amount and fertilizer application is accomplished with one pass. The approach is promising because it can account for both spatial and temporal variation in N demand. Situations best suited for this strategy is when the uncertainty in N need is greatest. Specific examples include: 1) fields with extreme variability in soil type, 2) fields experiencing a wet spring/early summer (loss of applied N) and where additional N is needed, 3) fields that have received recent manure applications, 4) fields receiving uneven N fertilization because of application equipment failure or because of mis-calibrated equipment, 5) fields coming out of pasture, hay or CRP management, 6) fields of corn-after-corn, particularly when the field has previously been cropped in a different rotation, and 7) fields after a droughty growing season. Sensor-based technologies for crop N management can provide improved accuracy (with higher resolution), responsiveness to temporal factors, and better economics. Sensor-based methodologies are progressive, but their use will be contingent on positive visual feedback to farmers as they apply N in their fields. Adoption of these sensors for N management will be promoted once profitability is demonstrated and environmental benefits are documented.