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Active-Crop Sensor Calibration Using the Virtual-Reference Concept

Active-Crop Sensor Calibration Using the Virtual-Reference Concept . K. H. Holland (Holland Scientific) J. S. Schepers (USDA-ARS, retired). 8 th ECPA Conference 2011. N-rich. other N rates. check. “ N-Rich ” Reference. Postage-stamp calibration Ramped calibration strip

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Active-Crop Sensor Calibration Using the Virtual-Reference Concept

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  1. Active-Crop Sensor Calibration Using the Virtual-Reference Concept K. H. Holland (Holland Scientific) J. S. Schepers(USDA-ARS, retired) 8th ECPA Conference 2011

  2. N-rich other N rates check “N-Rich”Reference • Postage-stamp calibration • Ramped calibration strip • Randomized calibration block (field strips)

  3. Modified Postage Stamp check • Combine-width plots • Randomized except check plot • Each block of treatments should have minimal soil variability • Repeated replications

  4. check N-Rich Modified Calibration Ramp • Standard ramp of plots • No randomization • Each N rate in the ramp has a nearby check and adequate N reference • Could randomize N rates in the ramp strip

  5. Commercial applicators and large producers - - TELL US : • N-rich strips are problematic • May be hard to locate (legal problems) • Need to move each year • Can not expect operators to understand how the algorithm and sensor calibration work • Need a “turn-key” approach that does not require N-rich strip or highly-skilled operator • Algorithm needs to be simple, versatile, and easy to adapt for local conditions

  6. Algorithms • based on predicted yield potential (Oklahoma State University) (GreenSeeker) 2) based on producer-set minimumandmaximumN rates (Europe & Missouri) 3) based on extension of crop N-response function (Holland and Schepers) Note:All algorithms use sensor data that are normalized to “healthy crops” .

  7. In-Season N Management Crop vigor during the growing season is proportional to yield at harvest

  8. How to Characterize Healthy Crops ? • N-Rich Strip (or Ramp Calibration Strip) average(as with plot studies) programmed (highest 3 consecutive seconds) • Normal Field Transects identify healthy plants from frequency distribution of all plants (histogram) (MS Excel)

  9. Mexico -White Corn, 2010 Crop Circle 600 m @ ~6 kmph

  10. 95 Percentile 3% lower Mexico -White Corn, 2010 Crop Circle 600 m @ ~6 kmph 3-second Running Average = 5.057 95 Percentile = 5.206

  11. Field Average

  12. SI = = 0.85 4.47 5.21

  13. N Credits Preplant N Field Reference EONR Producer Optimum Sufficiency Index Back-Off Strategy SI to start cutback SI to cut-off N Accumulation (based on growth stage) Spatial Soil / Topography Adjustment Algorithm

  14. √ (1 – SI) ∆SI Farmer Rate or NEONR S e e Holland K.H. and J.S. Schepers. 2010. Derivation of a variable rate nitrogen application model for in-season fertilization of corn. Agronomy Journal 102:1415-1424. √ Nappl =( Nopt – Ncred )

  15. Uniform Rate

  16. N Rates (0, 50, 100, 150, 200 kg/ha)

  17. OptRx Soybean Previous Year Check Plot

  18. 95 Percentile

  19. 5% lower GreenSeeker CIred-edge values : 95 percentile 1.985 3-second average 1.889

  20. Irrigated Corn - 2009 V9 Growth Stage 95 percentile

  21. Virtual Reference Strip (0-200 kg N/ha preplant) check

  22. Drive and Apply Mexico, 2010

  23. There’s Probably a Lot More Information in a Histogram than We Realize ! • Where’s it at ? • How to get it out ?

  24. Mexico 2010 - Irrigated Corn V5 Growth Stage SI = 0.7

  25. Mexico -White Corn, 2010 Crop Circle 600 m @ ~6 kmph 95% Cut-back level

  26. Conclusions • The virtual reference concept offers producers a convenient approach to quantify the vigor and chlorophyll status of crops for in-season N applications. • Histograms of active sensor data and related analyses offer a quick glimpse of where to focus management efforts. New sensors and tools will be needed to help fine tune management decisions.

  27. Thank You Jim Schepers 402-310-6150 james.schepers@gmail.com

  28. Historic Perspective • N-Rich treatment was initially used to normalize data from plot studies and allow leaf N concentration comparisons across time, fields, cultivars, etc. (1988) • Extended to normalization concept to SPAD meters. (1990) • Adapted to field situations and N-Rich strips to accommodate crop canopy sensors. (~2000)

  29. Historic Perspective • N-Rich plot concept extended to postage stamp arrangement with multiple N rates. (2002) • Ramped calibration strip with multiple N rates introduced. (2005) • Need for active sensor calibration technique to accommodate commercial applications. (2007)

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