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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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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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ngSub-Meter Application System is a Proven Concept

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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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Reduced Scale

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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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• Prescriptions should not be developed without considering rate controller performance.

• Worry about the macro variability within the field.

• Are you capturing the general trend?

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Randy TaylorRandy.Taylor@okstate.edu

405-744-5431

Questions