Evaluating polymer‐coated fertilizer prototypes designed for planting along with maize seed

Abstract

AbstractSide‐dress N is a management strategy in maize (Zea Mays L.) production that can increase yield, reduce N leaching, and increase the probability that N remains post‐flowering. This management adds cost, is time‐sensitive, and can be difficult due to field shape and topography. A plantable, polymer‐coated urea N bead of two sizes and two coating thicknesses was developed and field tested across multiple locations during 2015–2017 as a replacement to side‐dress application. Locations differed in previous crop history and the initial N rates applied prior to treatments. Bead performance varied among locations but averaged 0.3 Mg ha−1 compared to an uncoated control or in‐season urea‐ammonium‐nitrate (UAN) application. Bead application increased yield 0.8 Mg ha−1 when rainfall exceeded 225 mm between planting and R1 (silk appearance) but did not improve yield when rainfall was <125 mm. Nitrogen release from the bead was described by a thermal time function. A common exponential decay function was not adequate to describe the release of N across all locations indicating variation in release of N among locations driven by factors other than soil temperature. Slow‐release, polymer‐coated fertilizer, placed near the seed at planting, provides the option to apply supplemental N at planting, followed by N release later in the season, eliminating the need for in‐season applications. Further research is needed to more closely match coating thickness and N release to crop N demand consistently across locations and development of equipment to enable one‐pass seed planting and N application operations.