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The Use of Red and Green Reflectance in the Calculation of NDVI for Wheat, Bermudagrass, and Corn

The Use of Red and Green Reflectance in the Calculation of NDVI for Wheat, Bermudagrass, and Corn. Robert W. Mullen SOIL 4213 . Background of NDVI. Normalized Vegetative Index Current equation used in wheat and bermudagrass NDVI = (NIR ref - Red ref )/(NIR ref + Red ref )

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The Use of Red and Green Reflectance in the Calculation of NDVI for Wheat, Bermudagrass, and Corn

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  1. The Use of Red and Green Reflectance in the Calculation of NDVI for Wheat, Bermudagrass, and Corn Robert W. Mullen SOIL 4213

  2. Background of NDVI • Normalized Vegetative Index • Current equation used in wheat and bermudagrass • NDVI = (NIRref - Redref)/(NIRref + Redref) • Excellent predictor of biomass and N uptake in bermudagrass and wheat

  3. What does the sensor see when measuring NDVI?

  4. Biomass vs NDVI

  5. N uptake vs NDVI

  6. Red NDVI Limitations • When a large amount of biomass is present red NDVI reaches an adsorption maxima • Plants are absorbing the maximum amount of red light • No longer able to differentiate yield levels in this region of red NDVI

  7. Red Adsorption Maxima Red adsorption maxima

  8. Green NDVI in Corn • Work in corn shows that green NDVI is highly correlated with final grain yield (Shanahan et al., 2001) • Data collected using aerial imagery at 0.5 m resolution • Four bands were measured: blue (450-520 nm), green (520-600 nm), red (630-680), and NIR (775-900 nm)

  9. Green NDVI in Corn • Green NDVI calculated by:(NIRref – Greenref)/(NIRref + Greenref) • Corn ranged from stage V6 – R3 • R values nearing 0.8 (highly significant) • GNDVI more significant at later stages of growth (after tasseling)

  10. Green NDVI in Corn 1997 Data 1998 Data

  11. Using an Index that Utilizes Both Red and Green May Be Possible • Calculate NDVI using the following equation: • RGNDVI = (NIRref – Greenref – Redref) (NIRref + Greenref + Redref)

  12. So, how well does it work? • Various indices versus biomass and forage N uptake in bermudagrass

  13. How well does it work in wheat? • Various indices versus biomass and forage N uptake in winter wheat

  14. Discussion • Currently, no wheat or corn yield data to verify this hypothesis • If NDVI measures are made early enough in the season (prior to high biomass) Red NDVI may still be the more effective way of yield prediction

  15. Conclusions • Calculation of NDVI using red and green reflectance may improve yield prediction of wheat and corn • If sensor readings are collected at early growth stages this technique may not improve yield prediction • This must be verified in wheat and corn

  16. Questions??

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