Slow release versus water soluble fertilization affects nutrient leaching and growth of potted chrysanthemum

In two experiments, 'Charm' and 'Delano' chrysanthemum [Dendranthema x grandiflorum (Ramat.) Kitamura] were grown in a peat-based root medium using standard greenhouse cultural practices. Fertilization treatments included (1) alternate liquid fertilization (ALF): water-soluble formulation of 15N-4.3P-24.9K (15-10-30) at 536 mgL(-1) N alternated with tap water irrigation; (2) Constant Liquid Fertilization (CLF): 15N-4.3P-24.9K (15-10-30) at 268 mgL(-1) N applied at each irrigation; (3) slow release resin-coated fertilizer (SRR): slow release formulation of 12N-4.3P-14.1K (12-10-17); and (4) slow release tablets (SRT): slow release formulation of 14N-1.7P-4.9K (14-4-6). Irrigation volume and timing of application were arbitrary for all plants in the first experiment, but they were determined gravimetrically for each treatment in the second experiment. Irrigation volumes exceeded container capacity by 20 to 30% (leaching fractions of 0.2 to 0.3). Leachate had lower electrical conductivity and higher pH with the slow release products than with liquid fertilizer. All treatments except SRT produced plants which met commercial crop standards and had adequate nutrient levels in shoot tissue. However, root dry mass was higher with slow release fertilizer than with liquid fertilizer. Root:shoot ratios were ranked SRT>SRR>ALF=CLF. Root data suggest that an advantage of SR fertilization over LF fertilization is that greater root mass will develop. Estimations of nitrogen (N) recovery in Experiment 2 suggest that chrysanthemums grown with SRR resulted in most efficient uptake of fertilizer with 64 to 68% of applied N recovered in plant tissue (compared to 41 to 46% from LF treatments) and 18 to 21% recovered in container leachate (compared to 32 to 41% from LF treatments).