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Comparison of hydroponic solutions for poinsettia nutritional studies

Whipker, B.E., Hammer, P.A.
Journal of plant nutrition 1998 v.21 no.3 pp. 531-543
Euphorbia pulcherrima, hydroponics, nutrient solutions, calcium nitrate, potassium nitrate, nitric acid, trace elements, phosphorus, cultivars, leaves, stems, potassium, nutrient content, calcium, magnesium, roots, application rate, ammonium nitrate, ammonium compounds
Poinsettia cultivars Supjibi and Freedom were grown in eight hydroponic solutions to develop a baseline solution for further nutritional studies. Four solutions contained nitrogen (N) from Ca(NO3)2.4H2O and KNO3 (denoted as -NH4) and four contained Ca(NO3)2.4H2O, KNO3, nitric acid, and NH4NO3 as the N sources (denoted as +NH4). The four -NH4 and +NH4 solutions were further divided by an 1X or 2X rate of micronutrients [boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)] (denoted as 1X or 2X). A factorial of these four solutions at 2 concentrations (100 mg L-1 of N and potassium (K) and 15 mg L-1 phosphorus (P), or 300 mg L-1 of N and K and 46 mg L-1 P) was studied. Greater leaf and stem dry weight for both 'Supjibi' and 'Freedom' was observed in plants grown with the +NH4 solutions, with a larger increase occurring with 'Supjibi'. Leaf NH4-N content for both cultivars was higher for both the 100 and 300 mg L-1 N and K fertilization rates when NH4-N was included. The leaf K content was highest for the plants grown with the +NH4/2X solution for 'Supjibi', for both fertilization rates, and leaf K content increased as the K application rate increased. Results indicate that for nutritional studies with poinsettias, hydroponic solutions should include between 12.5% to 33% of the N in the NH4 form, a calcium:magnesium (Ca:Mg) ratio of 2:1, and a micronutrient concentration of mg L-1) 0.5, 0.02, 6.6, 0.5, 0.1, and 0.05, respectively, for B, Cu, Fe, Mn, Mo, and Zn, for adequate plant growth.