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1
Refining Response Index in Winter Wheat with the
Use of CVs D. B. Arnall, K. W. Freeman, K. L.
Martin, K. Girma, R. K. Teal, C. J. Mack, W. R.
Raun,B.Tubana, O.Walsh, B. Chung, and S.
MogesDEPARTMENT OF PLANT AND SOIL SCIENCES,
OKLAHOMA STATE UNIVERSITY
SUMMARY
Past research indicated that RINDVI under
estimates RIHarvest. A relationship between CV of
NDVI readings taken from a Green Seeker handheld
sensor and plant population was established. To
estimate stand uniformity, CV was incorporated
into the RI equation. This new formula showed an
improvement in the correlation between RI
predicted mid-season and RI at harvest.

• RINDVI had a better correlation with RIHarvest
  than did RINDVI-CV for the 04-05 crop year.
• No difference between mid-season RIs
  indices at the m2 scale at Feekes 6.

OBJECTIVES

• Evaluate the use of RINDVI-CV as a mid-
  season predictor of RIHarvest.
• Comparison of RINDVI collected from a 1 m2
  sub-plots with those collected from the 16 m2
  plots.

• RIHarvest values better correlated With
  RINDVI than RINDVI-CV at growth stage Feekes 6
  (16 m2 scale).

MATERIALS AND METHODS

• Experimental Design RCBD 4 N rates and 3
  seeding rates, with 3 replications.
• Locations Stillwater, OK., Perkins, OK.,
  and Hennessey, OK.
• Seeding rate 40, 80, 120 kg ha-1
• N-Rates 0, 40, 80, and 120 kg ha-1
• Plot Size
• 3.0 m x 6.0 m with a 1.0 m2 sub-plot in each
  plot.
• Collected optical sensor readings once a
  week with a GreenSeeker handheld sensor
  beginning at Feekes 3 and concluding at
  Feekes 10.5.
• Harvest
• Subplots were harvested with hand sickles.
• Main plots were harvested with a Massey Fergusson
  8XP Combine.

O K L A H O M A S T A T
E U N I V E R S I T Y

• No significant difference Between RINDVI
  and RINDVI-CV correlation with RIHARVEST at
  growth stage Feekes 6 (1 m2 scale).

• At growth stage Feekes 8 The correlation
  between predicted RI and RIHARVEST was improved.

• ADDITIONAL CONSIDERATIONS
• Excellent spring weather
• produced large early season biomass, contributing
  to high estimated RIs.
• Draught during flowering and grain fill
  resulted in a reduction in final grain yield and
  lower RIHarvest values.

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