Expression of Spatial Variability in Corn (Zea mays L.) as Influenced by Growth Stage Using Optical Sensor Measurements By-Plant Prediction of Corn (Zea mays L.) Grain Yield Using Optical Sensor Readings and Measured Plant Height

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Expression of Spatial Variability in Corn (Zea
mays L.) as Influenced by Growth Stage Using
Optical Sensor Measurements By-Plant Prediction
of Corn (Zea mays L.) Grain Yield Using Optical
Sensor Readings and Measured Plant Height

• K.L. Martin, W.R. Raun, M.L. Stone, J.B. Solie,
  K.W. Freeman, B. Tubana, B. Chung, R.K. Teal,
  D.B. Arnall, K. Desta, S. Moges, C.J. Mack, J.W.
  Lawless, O. Walsh, S. Holtz, K. Lawless

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Expression of Spatial Variability in Corn (Zea
mays L.) as Influenced by Growth Stage Using
Optical Sensor Measurements

• Four rows (30 m long) at each location (2
  locations, 2 years)
• In 2004, 2 rows of low population and 2 rows of
  high population at each site
• Accumulate NDVI readings using a GreenSeeker
  hand held sensor throughout the growing season
• Evaluate NDVI and CV of NDVI readings over time

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• Collect biomass and grain yield by harvesting
  each individual plant and computing yield in kg
  ha-1 for the entire row.
• Evaluate relationships between NDVI and biomass
  yield, grain yield, and plant spacing
• Evaluate relationships between CV and biomass
  yield, grain yield, and plant spacing

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NDVI Over Time
V3 V6 VT
R4
V3 V6 VT
R4
V6 VT
R4
V3 V6 VT
R4
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CV Over Time
V3 V6 VT
R4
V3 V6 VT
R4
V6 VT
R4
V3 V6 VT
R4
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Relationship of NDVI and CV of NDVI with Corn
Grain and Biomass Yields
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By-Plant Prediction of Corn Grain Yield

• Measure the distance of each
  
  plants location
• Calculate the area that each plant occupies
• Where
• Di is the area occupied by the ith plant
• di-1,di,di1 are the distances to the i-1, i,
  and i1 plants
• Average NDVI of each plant

• This bicycle was modified such that a
  GreenSeeker sensor head, power source, and shaft
  encoder could be used to determine distance for
  each NDVI reading recorded in the data file.

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• The unit was pushed along the corn row as
  illustrated
• White marker plates were used at the beginning
  and end of each row to designate the start and
  stop point
• The resulting data file included NDVI for each
  calibrated distance (approximately 1.1 cm) and
  sonar height (when sonar was used)

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Data Presentation
Individual data points collected every 1.1 cm
Average NDVI for each plant
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NDVI vs. Grain Yield at all sites (2003 and 2004)
INSEY vs. Grain Yield at all sites where height
was recorded
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Plant Height and Corn Grain Yield Prediction

• Plant height was used as a means of evaluating
  plant competition.
• Competition can be defined as
• 1. The process by which the activity or
  presence of one substance interferes with or
  suppresses the activity of another substance
  with similar affinities, as of antigens.
• 2. The simultaneous demand by two or more
  organisms for limited environmental resources.
• 3. The simultaneous demand by two or more
  organisms for limited environmental resources,
  such as nutrients, living space, or light.
• Source The American Heritage Dictionary (2000)

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3
4
5
1
2
Do these plants compete with one another? If they
do, what above ground parameter(s) can we use to
evaluate this? Does the proximity of the
competitor have an impact on the level of
competition?
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Plant Competition Equation
In a series of five plants, the height of plant
number 2 and 4 is compared to the average of the
height of their neighbors to assess the
competitive ability of plants 2 and 4 as compared
to the plant in question, plant 3. This value
generated from the first step of this process
(weighted average value of plant 2 and 4 in the
series) is then compared to the actual height of
plant 3 to result in a weighted comparison of the
competitive ability of plant 3 to its neighbors
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GYest is the estimated grain yield Cadj
is the competition adjustment factor D is
the linear distance occupied by each plant
INSEY is the in-season estimate of yield
The competition adjustment factor accounts for
the competitive ability of the plant in question
when considering its height against those that
surround it. This value is then divided by the
linear distance to adjust the index due to the
change in proximity of the competitive plants (a
closer proximity to the competitive plant will
divide by a smaller number resulting in more
emphasis being placed on the height comparison).
The resulting value is then multiplied by INSEY
to allow for an incorporation of biomass produced
per day.
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By-Plant Prediction of Corn Grain Yield
Yield Prediction Using INSEY
Yield Prediction Using GYest
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Questions??