Modeling nutrient uptake in poinsettia as a function of growth rate
Abstract
Correlating nutrient uptake to specific physiological stages of plant development is essential to developing a fertility program that maximizes nutrient uptake and accumulation while minimizing wastage. The intent of this study was to establish the nutrient uptake pattern during progressive stages of physiological development for 'Supjibi' poinsettias grown in 100-15-100, 200-30-200, and 300-46-300 mg$\rm\cdot l\sp{-1}$ of N-P-K. No significant differences in total plant N, P, K, Na, B, Mo, or Cu content existed among the three fertilization rates, but increasing the fertilizer application rate above 100 mg$\rm\cdot l\sp{-1}$ N and K and 15 mg$\rm\cdot l\sp{-1}$ P resulted in a decreased total plant content of Ca, Mg, Mn, and Zn, while increasing the total plant Fe content. The results of the weekly nutrient uptake based on the total plant nutrient content in this study suggests that weekly fertilization rates should increase over time from potting until anthesis. Rates (in mg) that increase from 23 to 57 for N (with 33% of the total N supplied in the NH$\sb4$-N form), 9 to 18.5 for P, 19 to 57 for K, 6 to 15 for Ca, and 3 to 8 for Mg can be applied without leaching to poinsettias and produce adequate growth in the northern United States. Fertilizer applications which correspond to the nutrient accumulation pattern in poinsettias (1X rate) and a double (2X) rate were compared to the practice of applying 200 mg$\rm\cdot l\sp{-1}$ N and K applied at every irrigation to determine the effects on the plant growth and nutrient concentration. Leaf tissue nutrient levels for all three fertilizer rates were within or exceeded the recommended ranges. Plant height and aerial shoot dry weights were similar for all three fertilizer rates, but less than values reported in other studies. The reduced growth of the plants resulted in a reduction of the amount of nutrients that were utilized and an increase in root medium EC and nutrient concentrations. Results indicate that poinsettias can be grown with lower fertilizer application rates than the current 250 to 300 mg$\rm\cdot l\sp{-1}$ of N and K that growers currently use.
Degree
Ph.D.
Advisors
Hammer, Purdue University.
Subject Area
Plant propagation|Botany
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