U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Nitrogen Availability Alters Mineral Nutrient Uptake and Demand in Container-grown Deciduous and Evergreen Rhododendron

Scagel, C.F., Bi, G., Fuchigami, L.H., Regan, R.P.
Journal of environmental horticulture 2008 v.26 no.3 pp. 177-187
nutrient availability, nitrogen, Rhododendron, nutrient uptake, nutrient partitioning, phosphorus, potassium, sulfur, calcium, magnesium, boron, iron, zinc, manganese, carbon, plant nutrition, nursery stock, leaves, stems, dry matter partitioning
One-year-old evergreen rhododendron (Rhododendron 'H-1 P.J.M.') and deciduous azalea (Rhododendron 'Cannon's Double') were grown with (+N) or without (N-defi cient) nitrogen (N) from May to September to determine the effects of N-availability on uptake, demand, and allocation of other mineral nutrients. A 7-fold increase in N uptake by rhododendron was associated with a 3 to 4-fold increase in the uptake rate of phosphorus (P), potassium (K), and sulfur (S) and ~2-fold increase in the uptake rate of magnesium (Mg) and calcium (Ca). A 6-fold increase in N uptake by azalea was associated with a 3 to 4-fold increase in uptake rate of K, Mg, and Ca uptake and ~3-fold increase in the uptake rate of P and S. This suggests when altering nutrient management strategies to optimize N uptake, proportional changes in other nutrients may not be required. N-defi ciency was also associated with defi ciencies in P, K, S and manganese (Mn) for rhododendron and P, K, S, Ca, and Mg for azalea. This suggests N-defi ciency decreased the ability of the plant to take up these nutrients; therefore, when altering nutrient management strategies to decrease N fertilizer use, the infl uence of lower N rates on the ability of plants to take up other nutrients should be considered. Ratios of N to P, K, S, boron (B), and iron (Fe) (N-ratios) for both cultivars were similar when N was not limiting to growth, indicating fertilizers with similar availability ratios for these elements in relationship to N could be used for both cultivars. Cultivars differed in N-ratios for Ca, Mg, Mn, and zinc (Zn) indicating availability of these elements in fertilizer in relationship to N availability may need to be altered for optimal growth of each cultivar. For both cultivars leaf N:P ratio over-estimated P uptake and stem N:P ratio underestimated P uptake; however N:P ratios based on both stems and leaves may be useful for evaluating co-uptake of P in relationship to N. Leaf N:K ratio and N:Ca ratio, and stem N:S ratio for rhododendron varied little during the experiment indicating these ratios may be useful for evaluating co-uptake of K, Ca, and S in relationship to N for rhododendron.