Vol 117 (2004): Proceedings of the Florida State Horticultural Society
Krome Memorial Institute (Tropicals)

Effect of foliarly applied urea and boron on nutrition and yield of 'Booth 7' and 'Lula' avocado trees

Jonathan H. Crane
University of Florida
Published December 1, 2004
  • persea americana,
  • nitrogen,
  • urea,
  • boron,
  • leaf analysis


From 1997 through 2000, a 4.4 acre orchard planted with 54-year-old 'Booth 7' and 'Lula' avocado (Persea Americana Mill.) trees at the Tropical Research and Education Center, Homestead, Florida was used to investigate the effect of foliar applications of boron (B) or urea on leaf B and nitrogen (N) content and crop yields. The urea trial included a non-urea spray control plus 100 lbs soil-applied N per acre/year, 10 lbs foliarly applied urea per acre/year plus 90 lbs soil-applied N per acre/year, or 20 lbs foliarly applied urea per acre/year plus 80 lbs soil-applied N per acre/year. The effect of four years of foliar urea applications on crop yields of 'Booth 7' and 'Lula' trees at the 0, 10 and 20 lb rate were inconsistent among years and cultivars. In general, leaf N levels increased immediately after urea applications but were similar to non-urea controls after ca. 30 days. Boron treatments consisted of three rates of foliarly applied B (0, 1 or 2 lbs per acre/year) and a nonsprayed control. Foliarly applied B at both rates had an inconsistent effect on crop yields of both cultivars. In contrast, leaf B content was higher for trees treated with 1 and 2 lbs per acre/year compared to non-treated control trees. Foliar application of urea and B at the rates tested did not consistently affect 'Booth 7' and 'Lula' crop yields but did increase leaf N and B content temporarily.