What Did the Check Plots Yield?

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What Did the Check Plots Yield?
J.S. SchepersG.E. Varvel
R. MullenGreg LaBarge
G. RandallJ. Vetsch
L. Bundy
R. Ferguson
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NUE Workshop

• Historical accounting of the past three workshops
• Charge for the 4th Workshop
• Improved algorithm for N fertilization
• Willingness to test the ideas of others

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Precision Sensing and NUE

• November 21-22, 1996, Lincoln, NE
• June 6-7, 1998, Lincoln, NE
• March 1, 1999, Stillwater, OK, Schepers Lecture
• July 19-20, 2001, Stillwater, OK  2X Strip
• January 17-19, 2002, Lincoln, NE
• June 10-12, 2002, Shelton, NE
• May 18-20, 2003, Stillwater, OK
• August 3-5, 2004, Lincoln,NE
• August 10-12, 2005, Columbia, MO
• August 7-9, 2006, Waseca, MN
• August ___, 2007, ?? Virginia, Ohio, Kentucky,
  Canada,
  Texas, Illinois, Kansas, Colorado,
  Idaho, Indiana
• Is this group/meeting necessary? Should it be
  part of ASA?

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2006 Objectives

• To delineate components needed within functional
  algorithms that employ active sensors.
• To develop agronomic relationships between active
  sensors and N management for other crops.
• To share ideas and concepts relative to improved
  NUE for corn production.
• To discuss results from the current regional
  project and identify improvements needed for
  collaborative sensor-based research.

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Questions

• Is the difference in N uptake (max yield and
  check plot) an indication of N demand? Test this
• Should N rates be based on a yield variable
  (yield goal, yield potential, predicted yield)?
• What is our Goal? To maximize NUE, agronomic
  yield, or farmer profit

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Sufficiency What would Roger Bray say?

• Sufficiency Nutrients are applied independent of
  yield level, restricted to immobile nutrients
• Should N rates be applied independent of yield
  level?
• Root system sorption zone (mobile)
• Root surface sorption zone (immobile)
• Liebigs law of the minimum Yield directly
  proportional to the amount of the deficient
  nutrient present and the crop content of the
  nutrient

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N uptake N Demand or N Supply G. Varvel (2006)

• It is interesting that you look at the
  difference in N uptake between the years and
  equate that to differences in demand, while I
  look at them and equate them to differences in
  the corn crops ability to utilize the N
  available, usually because of the climate
  (probably mostly water and temperature).

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J.S. Schepers (2006)

• High mineralization late in the growing season
  won't do much for check plot yields, but it will
  make the corn green and maybe jack up the stalk
  nitrate levels.
• Check plot yields are made in the spring because
  of limited nitrate leaching and early season N
  mineralization. One way or the other, these
  processes account for residual N levels in the
  spring and determine if the check plots get off
  to a good start or not.
• In the case of the check plots, we can be pretty
  sure that residual N will be low at the end of
  the growing season, so leaching losses would be
  low for them, even if there is a wet fall.
• Therefore, I'll bet that check plot yields are
  highly correlated with soil temperatures between
  the first of October and the first of June.
• Likewise, I'd put money on the fact that
  irrigated corn yields in Nebraska are highly
  correlated with solar radiation and temperatures
  (evening lows and daytime highs) during July,
  August, and the first half of September.

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J.S. Schepers (2006)

• Before we get too carried away with differences
  in N uptake for any given year, we need to
  consider what is driving the system toward the
  low end. In the spring it is limited N
  availability. So what is driving the system
  toward the high side? I'd say energy. In between
  is the N just waiting to be used if the factory
  can use it?

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Meisinger et al. (1985), Agron. J. 77602
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Olson (1980) SSSAJ 44514
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Theory

• Does the demand for N change from one year to the
  next?
• Is the N rate required for maximum yield
  dependent on yield level?
• Are maximum yields achieved at the same rate each
  year? Test this
• The difference in N uptake (max yield and check
  plot yield) reflects the difference in the corn
  crops ability to utilize the N available, usually
  because of the climate (probably mostly water and
  temperature)
• Considering the unpredictability of N
  mineralization (early or late season) would you
  expect the amount of N taken up in the check plot
  to be correlated with maximum yield?
• If the amount of N taken up in the check plot
  were correlated with maximum yield, would it mean
  that both (check and fertilized) were benefiting
  from N mineralization? (provided that N is
  limiting)
• If the amount of N taken up in check plots was
  correlated with maximum yield obtainable, could
  we say that the demand for N does not change from
  one year to the next?
• Why would NUE be correlated with maximum yield
  and not check yield?

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CORN
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CORN
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Calibration Stamp2002-2004
Ramped N Rich Strip2005
Agron. J. 2005 97 338-342
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Ramped N Rich StripVisual InterpretationOptical
Sensing
NDVI
RI 1.5
RI 1.5
Distance
0 50 100 150
N Rate
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Predicting Yield Potential in Corn
NDVI, V8 to V10

INSEY
Days from planting to sensing
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