Use of By-Plot CV

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Use of By-Plot CVs for Refining Mid-Season
Fertilizer N Rates

• Daryl Brian Arnall
• Plant and Soil Sciences Department
• Oklahoma State University

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Introduction

• Scrutiny of Nitrogen Application
• Rise in Nitrogen cost
• Environmental impact
• Precision Nitrogen Application
• Great Potential
• Reduce Application Levels
• Use of Statistical Analysis for Improving
• Application Not Completely Examined
  

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Objective

• Determine the relationship between the CV
  measured using spectral radiance measurements,
  and plant population at early growth stages.
• Sensing direction in relation to the crop row
  direction impact on NDVI.

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Method

• 25 plots at 3 locations
• Plots measured 1.48m by 4.88m
• 3 nitrogen treatments implemented with each plot.
• 0 N, 120kg/ha Fall App., 80 kg/ha Top-dress

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Plot Plan
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Method cont.

• At Feekes 1 (Emergence)
• Plots were established.
• Fall nitrogen applied.
• Plant counts taken on 4 randomly selected rows.
• At Feekes 6 (Stem Elongation)
• Topdress nitrogen applied

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Method cont.

• Sensing
• Began in January.
• Concluded at physiological maturity.
• Sensor held 75cm to 100 cm over the crop canopy.
• 3 seconds allowed for each reading.

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Sensing Plan
5 Readings per trt 2 with row, 2 across row,
and 1 at a 45 degree to the seed row.
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Sensing Plan
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Method cont.

• At Physiological Maturity
• A 1m2 area hand harvested from each plot.
• Thrashed with a mechanical thrasher.
• Grain weighed for yield.
• Processed and analyzed for N content.

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2004 harvest
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Results
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CV and Population
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CV over Time
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RI Hybrid
RI Response Index RIharvest Yield of N-rich
plot / Yield of the
check RIndvi NDVI of N-rich plot / NDVI of
check plot
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Sensor Direction
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Directional CV
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Conclusion

• High CVs from sensor NDVI readings can be used
  as an indicator of poor plant stands.
• CV can be used to improve determination of RI.
• Seed row direction had no effect on NDVI Readings.

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Questions?