Spread pattern problems on spinner spreaders
click image to zoomGreen and yellow streaks in wheat following fertilizer application. Alternating streaks of dark green and pale green are not uncommon in wheat in the spring and often follow the path of the nitrogen fertilizer application made earlier in the season. Although very noticeable in wheat, non-uniform application of fertilizer is a common problem in many crops where granular fertilizer applications have been made with spinner spreaders.
Many of these problems can be traced back to three sources: operator error, poor quality fertilizer, and, occasionally, a misadjusted spreader.
The first step to diagnosing potential spreader problems is to obtain a copy of the operator’s manual for the spreader being used. In the operators manual there will be a wealth of information such as width of spread, proper hitch height, and operating speed as well as important safety information.
Common operator errors
After reviewing the operator’s manual, observe the operator making an application. Give particular attention to the operating speed of the spinners. Many drawn spreaders have mechanically driven spinners operating from the PTO of a tractor. The engine RPMs must be maintained at PTO operating speed. For hydraulic-driven units, adequate pressure must be maintained in the hydraulic system to drive the spinners at rated speed.
Check to see if the width of application is being maintained by the operator. Light bars, auto steer and other navigation aids can assist the operator in maintaining application width. Confirm that the selected width is appropriate for the spreader and the material being spread.
Hitch height is an important detail on drawn spreaders as it affects the pitch of the spinners at the rear of the machine. Consult the operator’s manual for the machine being used.
Wind speed should be less than 5 mph when making applications. Strong winds and especially gusting winds can significantly alter the spread pattern.
Quality of material
The quality of material being spread can affect spread pattern, particularly material that contains a significant amount of very fine particles (dust) or large clumps.
Large clumps can partially block off the opening under the gate, reducing the rate of application by reducing flow. To avoid large clumps from forming, keep fertilizer as dry as possible.
Material that contains a significant amount of dust and small particles will be more difficult to spread evenly with spinner-type spreaders (it’s hard to throw dust). To avoid making fertilizer dust, reduce handling as much as practical, especially with augers.