variable rate fertilizer at reduced scales
DESCRIPTION
Variable Rate Fertilizer at Reduced Scales. Randy Taylor Biosystems and Agricultural Engineering Oklahoma State University. 2010 NUE Conference Stillwater, OK. Field Scale Variability. Macro-variability Likely tied to soil type, landscape position, or something else Micro-variability. - PowerPoint PPT PresentationTRANSCRIPT
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Variable Rate Fertilizer at Reduced Scales
Randy TaylorBiosystems and Agricultural Engineering
Oklahoma State University
2010 NUE ConferenceStillwater, OK
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Field Scale Variability
• Macro-variability– Likely tied to soil type, landscape position, or
something else• Micro-variability
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App
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Rat
e, g
pa
RX_RATERATE
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Variability View from Equipment
• Longitudinal– Down-the-row– Response time issues
• Lateral– Across the boom– Boom divisions
A greater distance between the control and delivery points means a lower resolution and increased scale.
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Liquid Systems
• The initial sub-meter application system met market resistance
• However, sensor based VRA has found commercial success
• Section control systems have also renewed the interest in sub-boom width application
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Accepted Resolution
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0 20 40 60 80 100
Min
imum
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pons
e Tim
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Application Scale, ft
5 mph10 mph15 mphLimit
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Reduced Scale
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0.5
1.0
1.5
2.0
2.5
3.0
0 5 10 15 20
Min
imum
Res
pons
e Tim
e, s
Application Scale, ft
5 mph10 mph15 mphLimitLimit
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Liquid Systems
• Most commercial rate controllers can be set to about a 2 second response time.
• Multiple control sections will require multiple control valves and possibly flow meters.
• Pulse width modulation and binary valve systems have promise.
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Granular VRT
• Granular distribution/delivery systems follow two basic designs– Gate/belt or chain/spinner– Metering wheel/air boom
• While both systems can be used for variable rate application, reducing the application scale to a partially width is really not feasible
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Spinner Spreaders• Reducing application scales
with spinner spreaders is really not feasible.
• The material is centrally metered and distributed.
• Furthermore, VRA with spinner spreaders is a challenge.– Spread distribution patterns
are typically a function of flow rate onto the spinner
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Air Boom Systems
• The material is centrally metered, but patterns are created locally.
• The primary challenge is lag time from the metering system to the point of application
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Potential Solutions
• The central hopper/conveying system might be a good model to follow
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Section Control System Speed
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Rate Controllers and Tuning
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0.0 0.2 0.4 0.6 0.8 1.0NDVI
Pres
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tion,
GPA 1 gpa/0.05 NDVI
2.5 gpa/0.05 NDVI
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RX_RATERATE
• Prescriptions should not be developed without considering rate controller performance.
• Worry about the macro variability within the field.
• Are you capturing the general trend?