Forest Nursery Notes Winter 2009 5 Using Polymer-coated Controlled-release Fertilizers in the Nursery and After Outplanting

Controlled-release fertilizers (CRF) are the newest and most technically advanced way of supplying mineral nutrients to nursery crops. Compared to conventional fertilizers, their gradual pattern of nutrient release better meets plant needs, minimizes leaching, and therefore improves fertilizer use efficiency. In our review of the literature, we found many terms used interchangeably with controlled-release, such as slow-release, but in this article, we will simply refer to all of them as controlled-release fertilizers (CRF). CRF can be divided into 3 categories based on their coating and nutrient composi-tion: 1. Uncoated, nitrogen-based fertilizers – This oldest class of CRF consists of chemically-bound urea and the release rate is determined by particle size, available wa