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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #229082

Title: Nitrogen Uptake and Mobilization by Hydrangea Leaves from Foliar Sprayed Urea in Autumn Depends on Plant Nitrogen Status

Author
item BI, GUIHONG
item Scagel, Carolyn

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2008
Publication Date: 11/20/2008
Citation: Bi, G., Scagel, C.F. 2008. Nitrogen uptake and mobilization by hydrangea leaves from foliar sprayed urea in autumn depends on plant nitrogen status. HortScience. 43:2151-2141.

Interpretive Summary: Rooted liners of Hydrangea macrophylla Cityline ‘Berlin’ were fertigated with different rates of nitrogen (N) (N07 treatment) from July to September 2007 and leaves were sprayed with 15N-labeled urea in late October to evaluate whether urea uptake and 15N translocation by hydrangea leaves depends on plant N status. Leaves rapidly absorbed 15N from urea sprays. The highest rate of 15N uptake occurred during the first 2 d after urea sprays and then decreased. Export of 15N from leaves occurred throughout the experiment, and the highest rate of 15N export occurred during the first 2 d after urea sprays and then decreased. There was little uptake or mobilization of urea N 5 d after spraying. Hydrangea plants with lower N status in the autumn were more efficient in absorbing and translocating N from foliar urea than plants with higher N status. These results suggest that when growing florists' hydrangea in Mississippi, overhead irrigation will have little influence on the uptake of N from urea sprays 5 d after spraying, and defoliation practices commonly used with florists' hydrangea will have little influence on mobilization of N from urea after this time. Therefore, urea sprays during the production of florists' hydrangea maybe used approximately one week before manual or chemical defoliation occurs without negatively affecting N uptake from urea or mobilization of N from urea sprays.

Technical Abstract: Rooted liners of Hydrangea macrophylla Cityline ‘Berlin’ were fertigated with different rates of nitrogen (N) (N07 treatment) from July to September 2007 and leaves were sprayed with 15N-labeled urea in late October to evaluate whether urea uptake and 15N translocation by hydrangea leaves depends on plant N status. Four plants from each N07 treatment were harvested before plants were sprayed with urea and 2, 5, 10, and 15 d after urea sprays. Total N and 15N content were assessed to determine urea uptake and 15N mobilization. Increasing rate of N fertigation increased plant N content, and plants contained between 55 and 796 mg N in October before being sprayed with urea. Leaves rapidly absorbed 15N from urea sprays. The highest rate of 15N uptake occurred during the first 2 d after urea sprays and then decreased. Export of 15N from leaves occurred throughout the experiment, and the highest rate of 15N export occurred during the first 2 d after urea sprays and then decreased. On both day 2 and day 5, the rate of 15N uptake by leaves and export from leaves decreased with increasing rate of N fertigation. On a whole plant basis, the total amount of 15N and the percentage of N that derived from foliar 15N-urea sprays increased with increasing rate of N fertigation. Regardless of plant N status, hydrangea plants take up and translocate N from foliar urea sprays for several days after plants are sprayed with urea and the highest rates of N uptake and export occur during the first 2 d following the urea application. Hydrangea plants with lower N status in the autumn are more efficient in absorbing and translocation N from foliar urea than plants with higher N status.