When applying fertilizer such as urea to plants it is often desirable to control (i.e. slow) the release of the fertilizer because too rapid release can damage the plants and is wasteful; valuable fertilizer components can be lost by leaching or degradation in the soil. One method for controlling release of fertilizer is to encapsulate the fertilizer by applying a coating.
The patent literature describes a multitude of fertilizer coating processes in detail. Polyurethane (PU) coatings have been known for nearly 50 years, but continue to be an active research area to this day.
PU-coated CRF were prepared using TERRIN™ polyols and tested as described below. For benchmarking, CRF was prepared using castor oil, a polyol widely referenced in the patent literature, and a variety of commercial CRF from different manufacturers were purchased at retail and tested by the same procedures.
Release comparable to the commercial benchmarks can be achieved even with lower coating weight.
Release can be tailored over a very wide range by selection of TERRIN™ polyol and adjustment of coating weight.
Figure 2 shows results of an extended release test comparing three commercially-available CRF with lab-prepared CRF made using TERRIN™ 170 polyol. The TERRIN™ 170 CRF performs similarly to the best commercial benchmark, Comparison A, even though it has much less coating weight.