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United States Department of Agriculture

Agricultural Research Service

Research Project: Determining Impact of Soil Environment and Root Function on Horticultural Crop Productivity and Quality Title: Effects of irrigation frequency and nitrogen fertilizer rate on water stress, nitrogen uptake, and plant growth of container-grown Rhododendron

Authors
item Scagel, Carolyn
item Bi, Guihong -
item Fuchigami, Leslie -
item Regan, Richard -

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2011
Publication Date: December 1, 2011
Citation: Scagel, C.F., Bi, G., Fuchigami, L.H., Regan, R.P. 2011. Effects of irrigation frequency and nitrogen fertilizer rate on water stress, nitrogen uptake, and plant growth of container-grown Rhododendron. HortScience. 46(12):1598-1603.

Interpretive Summary: The influence of irrigation frequency (same amount of water per day given at different times) and nitrogen (N) fertilizer rate on water stress, N uptake, and growth (biomass) of container-grown evergreen Rhododendron 'P.J.M. Compact' and ‘English Roseum’ and deciduous Rhododendron ‘Gibraltar’ was evaluated. Both N-deficiency and high N rate increased water stress. Altering irrigation frequency changed either the availability of N in the growing substrate or the ability of roots to absorb N. Transitory increases in plant water stress altered N uptake, N use, and plant form without detectable changes in total plant biomass. Decreasing the frequency of irrigation increases water stress of container-grown Rhododendron and plants grown with high rates of N fertilizer are more susceptible to water stress, particularly when plant water requirements are highest due to growth and environmental conditions.

Technical Abstract: The influence of irrigation frequency (same amount of water per day given at different times) and nitrogen (N) fertilizer rate on water stress (stomatal conductance, gs), N uptake, and growth (biomass) of container-grown evergreen Rhododendron ‘P.J.M. Compact’ and ‘English Roseum’ and deciduous Rhododendron ‘Gibraltar’ was evaluated. Both N-deficiency and high N rate increased water stress. Water stress was greatest in plants fertilized with the highest N rate and gs of plants grown with the higher N rates was more sensitive to water deficits resulting from irrigation treatments and seasonal climatic changes. Watering plants more frequently decreased water stress of plants fertilized with higher N rates and altering irrigation frequency had little impact on alleviating water stress of N-deficient plants. Increasing irrigation frequency decreased N uptake efficiency (N uptake per g N applied), increased N use efficiency (growth per g N uptake) and altered biomass allocation with little influence on total plant biomass. Response of biomass allocation to N rates was similar among cultivars and response of biomass allocation to irrigation frequency varied among cultivars. Altering irrigation frequency changed either the availability of N in the growing substrate or the ability of roots to absorb N. Our results indicate that transitory increases in plant water stress can alter N uptake, N use, and plant form without detectable changes in total plant biomass.

Last Modified: 11/27/2014
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