Foliar applied urea improves freezing protection to avocado and peach

• Published in: Scientia horticulturae Vol. 66; no. 1; pp. 85 - 92
• Main Authors: Zilkah, S., Wiesmann, Z., Klein, I., David, I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.1996; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Avocado; Biological and medical sciences; Freezing injury; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Nitrogen fertilization; Nitrogen, phosphorus, potassium fertilizations; Peach; Phytopathology. Animal pests. Plant and forest protection; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Urea; Weather damages; Weather damages. Fires; Avocado; Urea; Peach; Freezing injury; Nitrogen fertilization; Cold resistance; Rosaceae; Flower bud; Persea americana; Foliar application; Plant leaf; Prunus persica; Frost prevention; Orchard; Frost protection; Dicotyledones; Angiospermae; Application method; Spermatophyta; Fruit tree; Lauraceae; Protection
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/0304-4238(96)00883-7

The effect of foliar applied urea on freeze hardiness was evaluated under orchard and laboratory conditions. Freezing injury and senescence of avocado ( Persea americana Mill.) cv. ‘Hass’ leaves in the orchard was inversely correlated to N content. Three foliar applications of 2% low-biuret urea caused a 26% nitrogen enrichment of leaves. Consequently, leaf freezing hardiness was increased and senescence retarded. Urea-treated leaves were 2.5 times more tolerant to freezing than untreated leaves, at the same level of senescence. The freeze protection effect of foliar-applied urea was confirmed using potted plants of the cultivar ‘Fuerte’ under controlled conditions. Potted avocado plants treated with 2% low-biuret urea, gradually cooled, and exposed to −2 °C for 4 h, were significantly more hardy than control plants. Foliar application of 10% low-biuret urea to peach ( Prunus persica L.) cv. ‘Maravilha’ shoots before flowering, 3 days before frost occurrence, increased the freezing hardiness and survival of the reproductive organs. The protective effect of foliar-applied urea on peach flower buds in spring decreased gradually as bud development progressed.