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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #171257

Title: EFFECTS OF DEFOLIANTS (CUEDTA AND ZNSO4) AND FOLIAR UREA ON DEFOLIATION, NITROGEN RESERVES AND REGROWTH PERFORMANCE OF ALMOND NURSERY PLANTS

Author
item BI, GUIHONG
item Scagel, Carolyn
item CHENG, LAILANG
item FUCHIGAMI, LESLIE

Submitted to: Journal of Horticultural Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2005
Publication Date: 11/1/2005
Citation: Bi, G., Scagel, C.F., Cheng, L., Fuchigami, L.H. 2005. Effects of defoliants (cuedta and znso4) and foliar urea on defoliation, nitrogen reserves and regrowth performance of almond nursery plants. Journal of Horticultural Science and Biotechnology. 80:746-750.

Interpretive Summary: Chemical defoliation is widely used in many bareroot nurseries to facilitate autumn lifting, however the practice can be detrimental to the quality of nursery stock and decrease plant growth during the following growing season. Almond nursery trees, one-year-old and field-grown, were used to study the effects of defoliants (CuEDTA and ZnSO4) and foliar applications of urea on defoliation, nitrogen (N) reserves, and new growth the following spring. We found that CuEDTA was more effective than ZnSO4 in promoting early defoliation and that addition of urea to defoliant applications increased efficiency of both ZnSO4 and CuEDTA in promoting early defoliation. Plants treated with foliar urea in the fall prior to or with applications of chemical defoliants had higher nitrogen reserves compared to plants that received only defoliant treatments and generally had greater new shoot and leaf growth the following spring. We conclude that both CuEDTA and ZnSO4 are safe and effective in promoting early defoliation of almond nursery plants and that combining urea with defoliants (e.g. urea + CuEDTA) is effective in promoting early defoliation without negative effects on plant growth the following spring.

Technical Abstract: Almond nursery trees (one-year-old, field-grown, Nonpareil'/'Nemaguard') were used to study the effects of defoliants (CuEDTA and ZnSO4) and foliar applications of urea on defoliation, nitrogen (N) reserves, and new growth the following spring. Although both chemical defoliants significantly promoted earlier defoliation, CuEDTA was more effective than ZnSO4. Addition of urea to defoliant applications increased efficiency of both ZnSO4 and CuEDTA in promoting earlier defoliation. Plants treated with foliar urea in the fall prior to or with applications of chemical defoliants (e.g. the urea + defoliant treatments) had significantly higher nitrogen reserves compared to plants treated only with the defoliant. Nitrogen reserves were comparable in urea + defoliants treated plants to the levels found in naturally defoliated (control) trees. Compared to natural defoliation, the combination of urea and defoliants had no significant effect on bud break, or new shoot and leaf growth the following spring. Plants treated with urea and defoliants had greater new growth the following spring than plants treated with only defoliants. We conclude that both CuEDTA and ZnSO4 are safe and effective in promoting early defoliation of almond nursery plants and combining urea with defoliants (e.g. urea + CuEDTA) is effective in promoting early defoliation without negative effects on plant growth the following spring.