Management Zone Delineation for Iron Chlorosis Management

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Management Zone Delineation for Iron Chlorosis
Management

• Richard Ferguson, TayZa Kyaw, Viacheslav
  Adamchuk, David Tarkalson, Gary Hergert, Roger
  Elmore, Dennis McCallister
• University of Nebraska

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Iron Chlorosis
Interveinal chlorosis of leaves, appearing
first on younger plant tissue. Can result from
low soil iron levels, but in Nebraska is
more often due to the plants inability to
effectively utilize iron that is present, either
due to high soil pH, elevated carbonates,
saturated soil or combinations of the above.
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Iron Chlorosis
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Why Consider Variable Hybrid Management?

• Over 1 million acres of variably high pH soils in
  Nebraska there is also substantial acreage in
  Colorado, Kansas and Texas.
• Yield potential of corn hybrids vary
  significantly with soil pH - yield may be reduced
  by 50 for some hybrids on high pH soils.
• Hybrids adopted for chlorosis tolerance may yield
  less than other hybrids under non-chlorotic
  conditions.

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Study Objectives

• Evaluate options to delineate iron chlorosis
  management zones, and assess the stability of
  chlorosis-prone areas over years.
• Investigate the potential for site-specific
  hybrid management to improve overall productivity
  in fields with iron chlorosis pressure.

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Study Area Yield1998
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Study Area Yield1999
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Delta Yield - 1998 1999
33V08 - 33R06 Red-Yellow indicates 33V08
(tolerant) yielded better. Blue indicates 34R06
(susceptible) yielded better.
33R87 - 33G26 Red-Yellow indicates 33R87
(tolerant) yielded better. Green-Violet
indicates 33G26 (susceptible) yielded better.
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Study Locations, 2004-2005
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Spatial Information Obtained for Each Site

• Grain yield
• Historic DOQQ
• Mapped soil series
• Veris ECa (0-30 cm, 0-90 cm) and pH (15 cm)
• Grid sample pH, EC, Bray-1P, SOM
• Aerial photographs (natural color and NIR)

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Merrick County Site 1, 2004
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Merrick County Site 1, 2004-2005
Grid sample points
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Objective 1. What is the best way to delineate
chlorosis management zones, and are they stable
over time?
Merrick County, Sites 1 and 9
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Chlorosis Management Zones, Merrick Co., Sites 1
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Zones delineated with Management Zone Analyst,
Univ. Mo./USDA-ARS
Gray areas have relatively low chlorosis pressure
2004 yield, NDVI and deep ECa
2005 yield, NDVI and deep ECa
2004-2005 yield, NDVI and deep ECa
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Chlorosis Management Zones, Merrick Co., Site 5
Management zone delineation based on yield, NDVI
and deep ECa.
Chlorosis management zone delineation failed at
this site because another yield- limiting factor
was present (low water-holding capacity).
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Chase Co. Site 3, 2004
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Chase Co. Site 3
1999 DOQQ
Chlorosis-prone areas appear stable over time,
and aerial photos are a relatively inexpensive
means of management zone delineation
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Objective 2. Do hybrids perform differently in
areas of fields with differing chlorosis pressure?
Significant Pearson correlation coefficients
between hybrid yield and soil properties.
Veris pH was not significantly correlated with
yield at any site.
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Yield reduction due to chlorosis was evident only
at S/Y 1 and 5, both in Merrick Co.
S/Y 1
P34B99 (tolerant)
P34N42 (susceptible)
Yield reduction due to low water-holding capacity
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S/Y 5, Merrick County Grain Yield
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S/Y 3, Chase County Grain Yield
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Summary

• Historic yield, ECa, and aerial imagery can be
  useful in delineating chlorosis-prone areas
  within fields.
• Yield-limiting factors other than chlorosis can
  make chlorosis management zone delineation
  difficult or not possible.
• Aerial imagery appears to be the most
  cost-effective means of identifying stable
  chlorosis-prone areas.
• Site-specific hybrid management within
  chlorosis-pressure zones was not feasible with
  the two hybrids used in this study, as P34B99
  consistently out-yielded P34N42 regardless of the
  level of chlorosis pressure.
• Site-specific hybrid management could be possible
  with hybrids which differ more than those used in
  this study.