HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Scholberg, J. M. S. Articles by Morgan, K. T. Search for Related Content PubMed PubMed Citation Articles by Scholberg, J. M. S. Articles by Morgan, K. T. Agricola Articles by Scholberg, J. M. S. Articles by Morgan, K. T. Related Collections Irrigation Ecological Risk Assessment Nutrient Management Nitrogen

TECHNICAL REPORTS
Ecological Risk Assessment

Soil Temperature, Nitrogen Concentration, and Residence Time Affect Nitrogen Uptake Efficiency in Citrus

^a Agronomy Dep., 304 Newell Hall, Univ. of Florida, Gainesville, FL 32611
^b Univ. of Florida, Citrus Res. and Educ. Center, 700 Experiment Station Road, Lake Alfred, FL 33850
^c Soil and Water Science Dep., Univ. of Florida, IFAS, Gainesville, FL 32611

* Corresponding author (jmscholberg{at}mail.ifas.ufl.edu)

Received for publication October 10, 2000. We try to elucidate which environmental and soil factors control nitrogen uptake efficiency in citrus. Effects of residence time and nitrogen (N) concentration (three 500-mL applications of 7 mg N L^-1, representative of reclaimed water used for citrus irrigation in central Florida, or one 150-mL application of 70 mg N L^-1) on nitrogen uptake efficiency (NUE) of young citrus seedlings were studied. Increasing residence times from 2 to 8 h increased NUE from 36 to 82% and from 17 to 34% for high and low application frequencies, respectively. We developed a model to predict N uptake based on root density, N concentration, and soil temperature (T_s). Assuming a base temperature (T_b) of 10°C, N uptake temperature sum (UTS) = (T_s - T_b)/24 (°Cd_N, degree day units of N uptake). To eliminate the risk of N leaching for young seedlings, minimum uptake periods of 5 and 16°Cd_N were required at initial soil N concentrations of 0.9 and 2.5 mg N L^-1, respectively. After correcting for differences in root length, this information was then used to predict the effect of irrigation practices on N uptake from reclaimed water for mature trees. Applying 2500 mm yr^-1 vs. 400 mm yr^-1 reclaimed water reduced the NUE of N in this water from 100 to 63% during the summer and from 100 to 28% during the winter. Reductions in NUE at higher irrigation rates appeared to be related to N displacement below the root zone prior to complete N uptake.

Abbreviations: ET, evapotranspiration • N7, 7 mg N L^-1 treatment • N70, 70 mg N L^-1 treatment • NS, nitrogen supply • NU, nitrogen uptake • NUE, nitrogen uptake efficiency • T_b, base temperature for nitrogen uptake • t_R, residence time • T_s, soil temperature • UTS, uptake temperature sum

This article has been cited by other articles:

				L. Zotarelli, J. M. Scholberg, M. D. Dukes, and R. Munoz-Carpena Fertilizer Residence Time Affects Nitrogen Uptake Efficiency and Growth of Sweet Corn J. Environ. Qual., May 1, 2008; 37(3): 1271 - 1278. [Abstract] [Full Text] [PDF]