Evaluation Of Polymer-Coated, Controlled Release Fertilizers For Drip-Irrigated Tomato Production In Florida.

Plasticulture for vegetable crop production commonly utilizes drip irrigation systems that allow for fertigation and spoon feeding of nutrients to crops.  Such an approach to nutrient delivery is considered to be highly efficient in reserving fertilizer applications until needed and allowing for application rates that target specific demand periods of the crop.  Some drawbacks to fertigation include the expense and hassle of making multiple fertilizer injections and errors in application rates originating from irrigation system non-uniformity.  An alternative to fertigation involves the use of polymer-coated, controlled release fertilizers (CRFs).  By choosing the right CRF, nutrients can be delivered continuously to crops over the entire growing season from one fertilizer application at bedding.  Over the previous two growing seasons, fertigation and CRF programs were compared as nutrient delivery methods for fresh market tomato production at two locations in Florida. The effects of N rate (250, 200, and 170 lb N/A) and N source (polymer coated urea, polymer coated NPK, and fertigated ammonium nitrate) on fruit yield and quality, plant vigor, and plant nutrient levels were evaluated for surface drip-irrigated crops grown in sandy soils on raised, plastic-covered beds.  The results show that CRF programs perform equal to or better than the standard fertigation program at N rates equivalent to or lower than those recommended by the University of Florida Institute of Food and Agricultural Sciences (IFAS).  Among the CRFs tested, polymer-coated, homogeneous NPK fertilizers gave the most consistent response and increased tomato yields and quality over fertigation in one of two years tested.  Differences in costs between the two approaches, CRF and fertigation, may not be that large when total costs to fertigate are considered.  CRF offers a very simple, yet efficient approach to nutrient delivery that should be considered as a viable alternative to efficiency practices involving fertigation.