N Uptake In the Ornamental Plants In South Florida Related with Nitrogen Release Patterns Measured with Three Different Methods.

Abstract Five different formula of controlled release fertilizers (CRFs) were tested in water under 25 and 100 0C for the nitrogen release patterns. The ornamental plants (Ficus elastica ‘ robusta’ ) were grown in the greenhouse with the five CRFs. Weight loss method was used in the greenhouse to monitor nitrogen release from CRFs in the pots. At 25 0C, about 80 -100% of total N was released in 180days (d); at 100 0C, 100% N release was from 80 to 168 hours (h); and in the greenhouse only 31 to 83% of total N release were observed in 180d. Using regression equations developed for cumulative nutrient release as a function of release time at 25 and 100 0C, the release pattern at 25 0C could be predicated by a rapid release test at 100 0C. There was a significant correlation between N release rates in water at 25 0C and in pots for each of the five CRFs respectively. The correlation between N uptake by Ficus elastica ‘robusta’ and the N release in water at 25 0C or in the pots was significant. This study showed that a rapid technique at 100 0C can predicate nitrogen release rate in water at 25 0C while nitrogen release rate in water at 25 0C can predicate N release pattern in pots indicating N uptake pattern by growing plants with CRFs.