Slow-release Nitrogen Fertilizers in Vegetable Production: A Review

Slow-release nitrogen (N) fertilizers offer many potential benefits for vegetable production. In sandy soils, their use may lessen N leaching. If the slow-release fertilizer has a release pattern that matches crop needs, N uptake by the growing crop may become more efficient. Additionally, if slow-release fertilizers can be applied as a preplant application, production costs could be lessened, eliminating the need for multiple applications of soluble N fertilizer. Synthetic slow-release fertilizers can be separated into two general groups: those that are slow release as a byproduct of a chemical reaction (such as urea-formaldehyde), and those that are slow release via a sulfur, wax, or resin coating around the fertilizer prill. In vegetable crop research, much of the available literature has focused on use of sulfur coat urea and urea-formaldehyde, as they have been in the fertilizer market for 40 years. Newer research has evaluated resin-coated products. In most studies, use of slow-release N fertilizers as a preplant treatment did not decrease crop yield, but yield was rarely increased when compared with standard split applications of soluble N. Based on available research, the benefits of using slow-release N fertilizers in vegetable crop production will come from reduced environmental risk and savings in production costs.