(This Document is Issued by University of Massachusetts Extension, USA with respect to their own horticulture environment .Read at your own discretion. यह दस्तावेज़ अमेरिका के मैसाचुसेट्स एक्सटेंशन विश्वविद्यालय द्वारा , अपने बागवानी पर्यावरण के संबंध में जारी किया गया है| पाठक अपने विवेक का प्रयोग करें| )
Prebloom Nutrient Applications for Apple Trees
UMass Extension Factsheet F-126
Issued by University of Massachusetts Extension, Stephen J. Demski, Director,
Wesley R. Autio
Department of Plant & Soil Sciences
Maintaining adequate levels of mineral nutrients in trees is an essential aspect of orchard management. Soil
and foliar applications of these elements should occur only after careful observation of tree growth, bud and leaf
quality, yield, and fruit quality and after measurement of concentrations within the tree (through leaf analysis). With
regular observation and annual application, nutrient levels can be optimized and tree performance can be maximized.
However, environmental or management conditions often interfere with this process, resulting less than optimal
nutrient concentrations. Soil applications and postbloom foliar applications often can correct these deviations, but
one of the most critical phases of development in an apple tree is from the time growth begins through bloom, since
much development of floral parts occur during this period and the ability of flowers to set fruit is determined.
Prebloom nutrient applications can be used to supplement nutritional programs during this critical phase. Specific
elements that can be targeted during this time are nitrogen, boron, zinc, and copper. The information included in this
factsheet was derived from Orchard Nutrition Management by Warren Stiles and Shaw Reid (Cornell
Cooperative Extension Information Bulletin 219).
Nitrogen is a major element, required by all plants. Prebloom applications of nitrogen can be used to
supplement an existing nitrogen management program. Prebloom timing benefits the tree by providing the rapidly
developing flower and leaf buds with an adequate supply of nitrogen. Timing is between the tight-cluster and pink
stages of bud development. Use a grade of urea that has less than 0.25% biuret at a rate of 3 lbs per 100 gallons.
Urea tight cluster – pink Apply at 3 lbs/100 gal. Urea must have
less than 0.25% biuret.
Boron is a required element, but only in small amounts (35-50 ppm in leaf tissue). General programs include
annual soil applications in the early spring or annual foliar applications in the first and third cover sprays. If leaf levels
are low (less than 35 ppm) or if there is a desire to enhance the levels of boron for developing buds, a prebloom spray
can be used. Timing is at the tight-cluster stage of bud development. Any spray-grade boron source can be used.
Solubor® is the most commonly available. Do not use Solubor®, however, with pesticides in soluble plastic bags,
since it will alter the bag’s ability to dissolve properly.
Solubor® tight cluster Apply at 1 lb/100 gal. Do not exceed 8x
Other sources tight cluster Apply at 0.1-0.2 actual B/100 gal.
Zinc, like copper and boron, is a micronutrient, i.e. it is required only in small amounts (25-50 ppm in leaf
tissue). Zinc can be provided partially by zinc-containing fungicides, but if zinc levels are low, additional material
should be applied. Zinc sulfate is a potential source. It should be applied before silver tip, but interaction with frost
or oil sprays can result in significant damage to the tree. Chelated zinc is more safe and is the recommended approach
for delivering zinc. Several forms are available, but few have been tested with apple trees and may result in damage.
EDTA zinc chelates are the preferred materials. Prebloom timing can provide zinc at the critical stages of bud
EDTA zinc chelates tight cluster Apply at label rates.
Prebloom Tank Mixes
Nitrogen, boron, and zinc can be applied in a prebloom tank mix at tight cluster. These elements together
may enhance bud quality, improve the ability of the buds to overcome cold damage, and enhance fruit set.
Urea (<0.25% biuret) 3 lbs/100 gal
Solubor® 1 lbs/100 gal
EDTA zinc chelate At label rates