DIEFFENBACHIA GROWTH RESPONSES AND N LEACHING FROM CONTAINER-GROWN PLANTS FERTILIZED BY SEVERAL METHODS

The effect on greenhouse potted Dieffenbachia maculata ‘Camille’ growing on 80% unfertilised blond peat (pH 6.0) and 20% perlite (v/v) of different fertilization methods has been studied. The fertilization treatments were: F (control) - Standard fertigation (9,7 meq N L^-1; 10% NH₄⁺-N; 1,4 meq P L^-1; 4,3 meq K L^-1); CF- 30% of total N applied as soluble complex 17-8-14 (11,1% NH₄⁺-N and stabilized with DMPP) and 70% of total N like F; BF - Basacote Plus (16-8-12; 3,0 g L^-1) + 50 % of total N equal to F; C- 70% of total N as soluble complex 17-8-14 (11,1% NH₄⁺-N stabilized with DMPP). The experimental design was unifactorial with 29 pots per treatment. During the experiment nitrogen concentrations (nitrate and ammonium) in the leached solution were analysed; finally, height, leaf area, dry matter content and total concentration of nitrogen, phosphorous and potassium were determined. The fertilization method had a significant effect on the crop vegetative and bioproductive parameters, showing the treatments with complex fertilizers (CF and C) highest values of leaf area, plant height and dry matter production. Plant N concentrations were lower in treatments CF and BF than in control treatment. Treatment C had similar results than those of F; however, and due to higher biomass production, treatment C showed higher N extraction index and uptake efficiency. The control treatment (F) showed the highest rates of N lixiviation losses, the slow release fertilizer treatment (BF) the lowest. Complex and slow release treatments showed low rates of ammonium lixiviation losses.