Nitrogen (N)
New plantings
- If prepared properly, little N is needed the year of growth. Apply 0.6-1 ounce N per tree at bud break and again 4 weeks later.
Optimal levels
Leaf analysis (heavy crop will increase N by 0.2-0.3%)
- Hard cultivars - 2.2-2.4%.
- Soft cultivars - 1.8-2.2%.
Growth
- Nonbearing years - 0.5-2 feet of growth.
- Bearing years - 8-15 inches of growth.
Application
- If the percent N in leaves is greater than optimum, decrease N application by 10% for each 0.1% leaf N is above optimum.
- If the percent N in leaves is less than optimum, increase N application by 10% for each 0.1% leaf N is below optimum.
- For possible set improvement, apply urea (spray grade with less than 0.25% biuret) at tight cluster to pink at a rate of 3 lbs/100 gal and again at petal fall to seven days after petal fall at a rate of 5 lbs/100 gal.
Potassium (K)
New plantings
- Generally K is required only on bearing trees, except for newly cleared land or on particularly sandy or gravelly soil.
Optimal levels
Application
- Leaf analysis (heavy crop will have 0.4% lower)
-
- All cultivars - 1.2-1.8%.
- Deficient K - 120-180 lbs K2O/acre (200-300 lbs muriate of potash -- KCl).
- Optimum K - 60-90 lbs K2O/acre (100-150 lbs muriate of potash -- KCl).
- Excess K - discontinue for a year.
Magnesium (Mg)
Optimal levels
Leaf analysis
All cultivars - 0.35-0.50%.
Application
- Deficient Mg - use dolomitic limestone plus 15 lbs Epson salts/100 gal. in petal fall, first cover, and second cover sprays (avoid high temperatures or slow drying).
- Optimum Mg - continue present program.
Boron (B)
Optimal levels
Leaf analysis
- All cultivars - 35-50 ppm.
Application
- General program - 1-2 lbs B/acre/year to the soil or 1 lb solubor/100 gal in first and third cover sprays (do not apply later than 30 days after petal fall)
- Less than 25 ppm B 1.7 lbs solubor/100 gal in fall plus 1 lb solubor/100 gal prebloom or 1 lb solubor/100 gal prebloom, first, and third covers or 1 lb solubor/100 gal prebloom plus 2-3 lbs B on the soil
- 25 to 34 ppm B continue present program plus 1 lb solubor/100 gal at tight cluster or petal fall 35 to 50 ppm B continue present program
- More than 50 ppm B discontinue application for one year
- Foliar applications in the fall (postharvest before leaf drop) may improve flower development, pollination, and set. Spring applications (first and second cover) may improve recovery from cold damage.
Manganese (Mn)
Optimal levels
Leaf analysis
- All cultivars - 35-135 ppm.
Application
- Deficient Mn 4 lbs manganese sulfate/100 gal in the first cover spray, or 3 sprays of a Mn-containing fungicide.
Zinc (Zn)
Optimal levels
Leaf analysis
- All cultivars - 25-50 ppm.
Application
- Deficient Zn - 1 lb or 1 quart zinc chelate (EDTA)/100 gal at tight cluster and in the second cover spray.
Copper (Cu)
Optimal levels
Leaf analysis
- All cultivars - 7-12 ppm.
Application
- Deficient Cu - Bordeaux mix or copper sulfate (2 lbs/100 gal) at green tip to 1/4-inch green.
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