UNIFORMITY OF GRANULAR FERTILIZER APPLICATIONS WITH A SPINNER TRUCK

Abstract

Field tests were run using sample pans to assess the effect of wind speed, wind direction, fertilizer material, and swath spacing on both the uniformity and recovery of the applications. The pan deposits were used in conjunction with a computer program to develop the overlapped swath deposits. The uniformity of the deposits were material, wind speed, wind direction, and swath width dependent. The up-and-down and racetrack application patterns are equally effective with respect to the uniformity of the applied granular materials. A coefficient of variation (CV) of 15% corresponds to a maximum deposit that is 70% larger than the minimum deposit. Ammonium nitrate CVs . 15% were obtained under low speed, cross winds when swath widths were generally <10 m. With this material, the CVs increased as the swath width increased. For potash and ammonium nitrate, the largest and smallest CVs tended to be associated with headwinds and tailwinds, respectively. For 13-13-13 applications, a crosswind produced more uniform deposits than when the wind was blowing directly onto the windshield. The amount of nitrogen, phosphate and potash deposited during 13-13-13 applications were in direct proportion to the amounts applied. For all tests, only 12.8% of the CVs we calculated were . 15%. The average pan recoveries for potash, 13-13-13 and ammonium nitrate were 95.5%, 78.9%, and 54.4%, respectively. The range in these recoveries illustrate why pan recovery data should not be used to calibrate a spreader. The latter result is consistent with prior research results.