By-Plant N Management

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By-Plant N Management

• Oklahoma State University

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Scale
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Ames, IA
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Ames, IA
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Stillwater, OK
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By-Plant N Management
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Paul Hodgen, Jim Schepers, 15N

• 60 of by-plant N accounted for in individual
  plants

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Ames, Iowa
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Shelton, NE
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Ames, IA
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Agron. J. 971603-1611

• At the sites with the highest average corn grain
  yield (11478 and 14383 kg ha-1, Parana Argentina,
  and Phillips, NE), average plant-to-plant
  variation in yield was 4211 kg ha-1 (67 bu ac-1)
  and 2926 kg/ha (47 bu ac-1), respectively.  As
  average grain yields increased, so too did the
  standard deviation of the yields obtained within
  each row.  This clearly indicates that by-plant
  variability can be expected in high and low
  yielding environments.  Furthermore, the yield
  range (maximum corn grain yield minus the minimum
  corn grain yield per row) was found to increase
  with increasing yield level.  This work shows
  that regardless of yield level, plant-to-plant
  variability in corn grain yield can be expected
  and averaged more than 2765 kg ha-1 over sites
  and years.

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• Causes for Delayed and uneven emergence
• variable depth of planting
• double seed drops
• wheel compaction
• seed geometry within the furrow
• surface crusting
• random soil clods
• soil texture differences
• variable distance between seeds
• variable soil compaction around the seed
• insect damage
• moisture availability
• variable surface residue
• variable seed furrow closure
• volunteer
• early season root pruning (disease, insect)

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5-Plant Sequence
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Formula
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Treatment Structure
Trt Pre-plant kg ha-1 Top-dress (V8-V10) kg ha-1 Method
1 45 22 By plant at base
2 45 22 By row at base
3 45 22 DSB at center
4 45 45 By plant at base
5 45 45 By row at base
6 45 45 DSB at center
7 45 90 By plant at base
8 45 90 By row at base
9 45 90 DSB at center
10 45 180 By plant at base
11 45 180 By row at base
12 45 180 DSB at center
13 0 0 -
14 45 0 Broadcast
15 225 0 Broadcast
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Methods of placement
By-plant
By-row
Between rows
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SED 1.15
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SED 0.55
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Results

• By-plant fertilization method had slightly higher
  yields in five out of six site-years, especially
  at the low N rate.
• In five of six site years the middle N rates of
  67 and 90 kg N ha-1 showed grain yields as high
  as or higher than the 135 and 225 kg N ha-1 N
  rates.