|BI, GUIHONG - MISSISSIPPI STATE UNIVERSITY|
|FUCHIGAMI, LESLIE - OREGON STATE UNIVERSITY|
|REGAN, RICHARD - OREGON STATE UNIVERSITY|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2011
Publication Date: 2/1/2012
Citation: Scagel, C.F., Bi, G., Fuchigami, L.H., Regan, R.P. 2012. Irrigation frequency alters nutrient uptake in container-grown Rhododendron plants grown with different rates of nitrogen. HortScience. 47(2):189-197.
Interpretive Summary: The influence of irrigation frequency (same amount of water per day given at different times) on nutrient uptake of container-grown evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown with different rates of nitrogen (N) fertilizer was evaluated. Changes to irrigation strategies and N fertilizer rates that cause low levels of water stress during container production of Rhododendron can alter nutrient uptake and use without restricting growth. To optimize efficiency of fertilizer use, fertilizer formulations may need to be adjusted when altering irrigation or N rate in container production of Rhododendron. Irrigating plants once per day to container capacity early in the growing season may be more beneficial for nutrient uptake than irrigating plants more frequently. Additionally, increasing irrigation frequency later in the growing season when plants are grown in conditions with greater potential for water stress may improve uptake of certain nutrients.
Technical Abstract: The influence of irrigation frequency (same amount of water per day given at different times) on nutrient uptake of container-grown evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown with different rates of nitrogen (N) fertilizer was evaluated. Increased N application rate increased nutrient uptake and plant dry biomass. Irrigation frequency did not significantly influence total plant dry biomass; however, more frequent irrigation decreased net uptake of several nutrients, including P, B, and Mn uptake in all cultivars; K, Cu, and Zn uptake in AZ and ER; S uptake in ER and PJM; and Fe uptake in AZ. Additionally, more frequent irrigation of evergreen cultivars increased Ca uptake. Covariate analyses was used to compare nutrient uptake among cultivars and irrigation treatments after accounting for the variability in nutrient uptake attributable to differences in biomass and N uptake. For most nutrients, the influence of irrigation frequency on uptake was partially attributable to differences in biomass and N uptake. After accounting for the variability in nutrient uptake associated with biomass or N uptake, increased irrigation frequency decreased P, S, B, Cu, and Mn uptake only in ER and increased Ca uptake in the two evergreen cultivars. Differences in nutrient uptake among cultivars in response to irrigation treatments were related to water and N availability during production and their combined influence on water stress, nutrient uptake, and biomass partitioning. Estimates of nutrient demand and uptake efficiency using nutrient concentrations and ratios are discussed in relation to nutrient management differences for different cultivars and irrigation treatments.