Remote Sensing of Winter Wheat Tiller Density for Early Nitrogen Application Decisions
- Michael Flowers *a,
- Randall Weisza and
- Ronnie Heinigerb
There is increasing evidence that scouting of winter wheat (Triticum aestivum L.) fields to determine tiller density at Growth Stage (GS) 25 is useful in deciding if N should be applied. However, to obtain an accurate average of field tiller density, frequent and intensive measurements must be made. A solution to this problem may be remote sensing. The objectives of this study were to determine (i) if a spectral index or digital counts in the near infrared (NIR), red (R), green (G), or blue (B) wavelengths could be used to estimate GS-25 tiller density across environments and (ii) if the inclusion of within-field references would improve the estimation of GS-25 tiller density for determining N recommendations. Research was conducted at four site-years in 1998 and 1999 using two wheat varieties. At three locations, a randomized replicated strip-plot design with three seeding rates was used. The fourth location was an on-farm test with one seeding rate. Spectral indices and individual NIR, R, G, and B digital counts were tested for correlation with tiller density at each site. Tiller density at GS 25 and NIR digital counts were found to be consistently correlated (0.67 ≤ r ≤ 0.87). The inclusion of within-field tiller density references resulted in a high correlation (r = 0.88) between relative tiller density and relative NIR digital counts across environments. Using relative NIR digital counts to predict tiller density would have resulted in the correct N recommendation 82% of the time.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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