Remote sensing of sugarbeet canopies for improved nitrogen fertilizer recommendations for a subsequent wheat crop

Return to soil of high N, green sugarbeet (Beta vulgaris L.) tops, but not the return of low N, yellow to yellow-green tops, reduces the magnitude of N-fertilizer responses for the following crop. Twelve N fertilizer trials w ith spring wheat (Triticum aestivum L.) were established at sites with late -season 'green' (8 sites) or 'yellow' (4 sites) sugarbeet canopies the prev ious year. Late-season, aerial color photographs of sugarbeet fields and gl obal positioning system (GPS) technology were used to locate the experiment al sites. Based on the soil NO3-N test customarily used in the Northern Gra in Plains, N fertilizer responses were expected at 11 of the 12 sites. Howe ver, no significant grain-yield responses were obtained at the eight antece dent 'green' sugarbeet sites. Expected yield and grain-N responses were obt ained at the four antecedent 'yellow' sites. In contrast to the usual soil NO3-test, remote sensing of the previous sugarbeet crop resulted in success ful prediction of N-fertilizer responses at all 12 experimental sites. Appl ication of N fertilizer at the 'green' canopy sites increased the likelihoo d that excess soil NO3-N would be present after the wheat harvest. A precis ion farming technique, involving remote sensing of late-season sugarbeet ca nopies, use of GPS technology, and use of variable rate N-fertilizer applic ation is recommended for a wheat crop following sugarbeet.