BY-PLANT RESOLUTION

1992, At What resolution are there real biological differences

IOWAIOWA OKLAHOMAOKLAHOMA

Plant-to-plant variation, avg. 45 bu/acNebraska, Iowa, Virginia, Oklahoma, Argentina, Mexico, Ohio (46 transects)

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Grain Yield Over Linear Distance (Shelton, NE)158 ± 67

Holdrege silt loam, Minden, NE

Mean Yield vs Std. Dev.

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Mean Yield, kg/ha

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aOklahoma

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Mexico

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Virginia

StdDev =920.71 +5.16E-5 Yld2 - 2.7 E-9 Yld3

R2 = 0.498

Average corn grain yield plotted against the standard deviation from by-plant yield over 46 transects in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma.

318 bu/ac

Paul Hodgen, Univ. Nebraska, Dissertation AA13271926, Jan 1, 2007

Target plant acquired over 70% of the total depleted 15N fertilizer that was taken up

data revealed an individual corn plant acquires most of its N from within a radius of less than 0.5 m.

Plants lose yield potential by emerging as little as three days after their neighbors.

Large doses of N fertilizer could not increase the yield of late emerging corn plants.

Sensors to detect each plant

• GreenSeeker Sensor was mounted on a bicycle• Shaft encoder was used to assign distance to each sensor reading• Readings were taken once per centimeter

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Grain Yield = 15083 * GYest + 3315R2 =0.48

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EFAW, OK (2004)

LCB, OK (2004)

Hennessey, OK (2004)

EFAW, OK (2005)

LCB, OK (2005)

New by-plant yield prediction methods focus on a totally different approach

Can you recognize by-row differences in N response?

If the answer is yes, then the minimum resolution at which “precision agriculture” should operate is 30 inches (front/back, left/right)

Variable Rate Technology Treat Temporal and Spatial Variability Wheat, 0.4m2

Corn, by plant

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)

The impact of uneven stands takes place prior to the time that irrigation is employed whether using surface/furrow or center pivot systems.

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bu/a

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Variation in Wheat Yields, 3' increments(Lake Carl Blackwell)

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Variation in Wheat Yields, 3' increments(Manchester)

37 ± 9 bu/ac

34 ± 5.3 bu/ac

Summary

Farmer fields in the US, Argentina, and Mexico showed that plant-to-plant variation in corn grain yield averaged 2765 kg ha-1 or 44.1 bu ac-1 (Martin et al., 2005).

Current methods can predict by-plant yields Plant to plant variability in yield exceeds the

magnitude encountered for other agronomic variables

Adjusting multiple inputs by-plant is possible today