Effect of Nitrogen Availability On Mineral Nutrient Uptake and Plant Growth of Container-Grown Hydrangeas

Rooted liners of Hydrangea macrophylla 'Red Star' were fertigated with one of three nitrogen (N) concentrations (0, 140, or 280 ppm) in a modified Hoagland's solution from June to November. Every 3 weeks starting in June, plants in each N treatment (0 N, 140 N, 280 N) were destructively harvested to determine plant growth and mineral nutrient uptake. The 0 N plants did not accumulate any significant biomass during the experiment. Biomass accumulation pattern was similar between 140N and 280 N plants. Total plant dry weight of 140 N and 280 N plants increased slowly during the first 6 to 9 weeks after planting, increased rapidly between 9 and 21 weeks, and was relatively stable after 21 weeks. By the end of the experiment the 280 N plants accumulated 92% more biomass than 140 N plants. Plant nutrient (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, and B) accumulation followed the similar pattern as the total plant biomass accumulation for 140 N and 280 N plants. There was very limited uptake of all mineral nutrients during the first 6 to 9 weeks after planting. Uptake of all nutrients increased rapidly from 9 to 18 or 21 weeks, coinciding with the period of rapid plant growth. For plants that did not receive any N, there was no significant uptake of any mineral nutrients. Increasing N-availability increased the uptake of all nutrients. Results are discussed in terms of optimizing fertilizer use by modifying timing of fertilizer application during container production of Hydrangea macrophylla.