Factors that influence fertilizer application.

Prepare for 2019 spring fertilizer applications

By John Fulton and Trey Colley, Ohio State University Department of Food, Agricultural and Biological Engineering

We are moving into spring work quickly here in 2019, including the application of fertilizer. Whether fixed- or variable-rate fertilizer application, it is important that proper maintenance, setup and calibration of spreaders is carried out. Annual calibration is necessary for accurate and uniform application of fertilizers.

While technology on spreaders, especially variable-rate technology (VRT) spreaders, has significantly increased in the last 10 years, the technology being adopted does not directly correlate to accurate field performance. Crop yield can potentially be impacted if incorrect rates are applied or non-uniform application occurs. There are a number of variables that impact the quality of dry fertilizer application, which includes the operator, fertilizer source properties, applicator and conditions during application. Here are a few notes to consider as we approach spring with work related to making sure the right source is accurately placed at the right rate.

First, fertilizer applicator settings need to change for individual or blended fertilizer sources. The applicator settings may need to be adjusted based on different application rates and field operating conditions. Calibration should be part of a regular maintenance schedule for all application equipment. Uncalibrated applicators are like driving with a broken speedometer, you have a general idea of your speed but you may be under the speed limit (under applying) or possibly even over it (over applying)! Here are some key points to consider before heading out this spring to apply granular fertilizers.


Applicator setup

Fertilizer products vary in density and physical properties, therefore spreader setup in accordance to product is key. Review this online resource, http://ohioline.osu.edu/factsheet/fabe-5501 to better understand the effect of fertilizer material properties on field placement.


Annual and proper maintenance

Before operation, double-check these important maintenance points: proper conveyor tension, bearings, tire inflation, conveyer wear, and vane and spinner wear. Common problems include un-level spinners, spinners operating at different RPMs, damaged discs, spinners not centered evenly under chute, fertilizer build-up on parts, bent or cracked fins, and corroded hoppers or components.


Calibration procedures can vary between manufacturers and applicator models. However, two essential aspects exist for accurate field execution: metering to obtain the right rate and uniformity of spread onto the field.

Meter calibration from the bin in to spinners includes running the conveyor over a known time or distance then measuring the amount of dispensed product and comparing it to the in-cab display estimated amount. Adjustments to gate height and conveyor constant will help dial into an accurate metering. You will need to calibrate for different fertilizers since varying in density and properties. Equipment manuals outline the proper procedure and specific adjustments to make. These include consideration of spread uniformity — spinners to ground. Spreader distribution patterns can be hard to accurately evaluate without conducting a proper spread pattern test. Pan testing following standard protocol is required to evaluate spread uniformity. Consult with a spreader dealer on obtaining a spread pattern test kit.

Be sure to take good notes of settings for future reference. Note any calibration constants and setup information.

Field operation

Spread width or swath spacing needs to be maintained in order to prevent too much or too little overlap between swaths. If not already being used, guidance systems greatly reduce error and operator fatigue in spreaders/spreader trucks.

For proper setup, use the calibrated settings for a particular fertilizer including adjusting the product density within the in-cab display setup, using the correct spinner speed, and adjusting the chute to the proper position. Remember to operate at the specified spread width to ensure correct overlap with adjacent passes.

There is still time to calibrate. These six points help ensure accurate field execution:

  1. Type of fertilizer (use the correct product density),
  2. Proper maintenance,
  3. Meter calibration,
  4. Spread uniformity calibration,
  5. Correct spread width, and
  6. Proper setup.

Find additional information related to fertilizer application at the Ohio State University Digital Ag website under Precision Crop Management: https://digitalag.osu.edu/precision-ag/research-focuses/precision-crop-management


Dr. John Fulton, Associate Professor, can be reached at fulton.20@osu.edu. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research and Development Center, and the College of Food, Agricultural, and Environmental Sciences.

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