Table of Contents

Introduction

Test the soil one year in advance of planting apple trees, or two years before planting if pH adjustment may be necessary. The best time to thoroughly incorporate organic matter, phosphorus, potassium, and lime is before planting. These materials are required to optimize orchard productivity but do not move readily through the soil profile.

Manure can pose a food safety risk on many fruit crops. Ensure at least 120 days between manure application and harvest.

Manure contains beneficial organic matter and many macro and micronutrients. The organic nitrogen in manure is mineralized over time, providing nitrogen in diminishing quantities for several years. Adjust additional organic and inorganic nitrogen applications accordingly. Excessive nitrogen, particularly in the second half of the growing season, can result in poor fruit colour, reduced storability, excessive growth and delayed cold-hardening of the woody tissue, which makes trees more susceptible to winter injury.

Apply no more than 7 tonnes/ha of poultry manure (20 m³ liquid), 40 tonnes/ha of cattle manure (100 m³ liquid), and 35 tonnes/ha hog manure (65 m³ liquid). Since the nutrient content of manure varies greatly, have it tested for nutrients before application (see Manure nitrogen). Broadcast manure at moderate rates and work into the soil in late fall or early spring before planting. Do not put manure around newly planted trees because of potential winter injury. Reduce the rate of nitrogen, phosphorus and potassium fertilizers applied to adjust for the nutrients supplied by manure. Table 3-11. Average Fertilizer Replacement Values for Different Types of Manure, , shows the average composition of some manures and suggested reduction of fertilizer when manure is used.

For more information about food safety and the environmental impacts of manure application, see Manure nitrogen, and Use manure responsibly.

Probability of profitable crop response to applied nutrient:
HR = high , MR = medium, LR = low, RR = rare, and NR = no response
*For new plantings of apples; For established apple trees, use leaf analysis to estimate requirements of N, P and K.

Table 4-3a. Nitrogen Required per Tree at Various Tree Densities and Tree Ages, Growing in Sod* (PDF 118 kb)

* Trees/ha
Note: Reduce nitrogen rate by half if orchard is cultivated without sod between tree rows.
Note: Do not exceed 200 kg of actual nitrogen per ha per season regardless of number of trees per ha.
** Approximate grams of actual Nitrogen required per tree - These are approximate values. The exact amount of nitrogen to apply is a function of soil nitrogen level, cultivar, rootstock, soil moisture, etc. The best way to determine nitrogen requirements is with regular leaf analysis.
*** Use leaf analysis to determine nitrogen needs.

Table 4-3b. Nitrogen Required per Tree at Various Tree Densities and Tree Ages, Growing in Sod* (PDF 118 kb)

* Trees/ha
Note: Reduce nitrogen rate by half if orchard is cultivated without sod between tree rows.
Note: Do not exceed 200 kg of actual nitrogen per ha per season regardless of number of trees per ha.
** Approximate grams of actual Nitrogen required per tree - These are approximate values. The exact amount of nitrogen to apply is a function of soil nitrogen level, cultivar, rootstock, soil moisture, etc. The best way to determine nitrogen requirements is with regular leaf analysis.
*** Use leaf analysis to determine nitrogen needs.

Table 4-3c. Nitrogen Required per Tree at Various Tree Densities and Tree Ages, Growing in Sod* (PDF 118 kb)

* Trees/ha
Note: Reduce nitrogen rate by half if orchard is cultivated without sod between tree rows.
Note: Do not exceed 200 kg of actual nitrogen per ha per season regardless of number of trees per ha.
** Approximate grams of actual Nitrogen required per tree - These are approximate values. The exact amount of nitrogen to apply is a function of soil nitrogen level, cultivar, rootstock, soil moisture, etc. The best way to determine nitrogen requirements is with regular leaf analysis.
*** Use leaf analysis to determine nitrogen needs.

High nitrogen levels can result in excessive growth and incomplete tree hardening. Cover crops are strongly recommended to check late season growth in cultivated orchards, especially in new plantings. Cover crops such as Italian ryegrass, sown about July 1, take up much of the available nitrogen in the soil and will check the tree growth.

Fertilizer for bearing apples

Most bearing orchards require annual applications of both nitrogen (N) and potassium (K) fertilizer. These two elements significantly affect growth and productivity.

Nitrogen (N)

Nitrogen is necessary for many tree functions, including growth, fruit bud formation, fruit set and fruit size. Because of the complexity of nitrogen interactions with quality and production, the best guide for nitrogen rates is leaf analysis.

Cultivars differ in nitrogen requirements. A cultivar grown for processing could receive more nitrogen than one for the fresh market. In some situations, if fruit tends to be small, more nitrogen may be needed. Rootstocks, spacing and pruning also influence application rates.

Tree growth, foliage colour, fruit quality such as colour and storability, nutrient balance in leaves and soil are also important considerations.

Nitrogen rates

Given the variety of orchard systems, rootstocks, cultivars and soil types, the exact amount of nitrogen to apply varies. Use leaf analysis to evaluate the nitrogen needs of specific plantings. Table 4-3. Approximate Grams of Actual Nitrogen Required per Tree at Various Tree Densities and Tree Ages, Growing in Sod is an estimate of possible nitrogen requirements. When the tree canopy covers the available space, nitrogen fertilizer requirements level out and do not increase indefinitely with tree age. Orchards grown under clean cultivation require about half the nitrogen required by orchards grown in sod.

Nitrogen placement and timing

Phosphorus (P)

Phosphorus is not required in large amounts by apple trees. With a few exceptions, the level of phosphorus in Ontario soils is generally adequate. Phosphorus may be required for sod or cover crop maintenance. A soil test is the best way to determine if this nutrient needs to be added to the sod cover. If indicated, apply phosphorus before planting so it can be thoroughly incorporated in the soil. Phosphorus soil test values between 12 and 20 ppm are considered adequate for tree establishment and fruit production.

Potassium (K)

Potassium is important for fruit colour, winter hardiness, tree growth and disease resistance. Because an excess of potassium can lead to a deficiency of magnesium (Mg), avoid unnecessary potassium applications. Potassium soil test values between 120-150 ppm are considered adequate when planting fruit trees. Muriate of potash (0-0-60) is the most common form of potassium. If leaf analysis data is not available, use the approximate rates in Table 4-4. Approximate Grams of Muriate of Potash Required per 2.5 cm of Trunk Diameter at Various Tree Densities, Grown in Sod.

Apply no more than 3 kg of K₂O (5 kg of muriate of potash) per mature standard apple tree in a year, regardless of how severe the potassium deficiency. When you fertilize trees on dwarfing rootstocks, consult Table 4-4, for approximate rates of muriate of potash to apply. When the tree canopy has covered the space available, potassium fertilizer requirements level out and do not increase indefinitely with tree age. Leaf analysis is the most reliable guide to determine potassium requirements.

Placement and timing

Calcium (Ca)

Foliar application of calcium (Ca) to apples reduces the incidence of bitter pit and cork spot. Where these disorders have been a problem, apply four foliar sprays two weeks apart, beginning in mid-July. See Table 4-5. Calcium Foliar Sprays. Where more calcium is required, make additional applications by either beginning earlier around mid-June or by continuing until harvest.

Calcium advances fruit maturity, so the timing of harvest may need to be adjusted as a result of calcium foliar sprays.

Some formulations of calcium chloride (CaCl₂), if applied too close to harvest, have resulted in poor fruit finish. Calcium sprays must contact the fruit for uptake to be effective. Therefore water volumes capable of wetting the entire tree are required. The more calcium applied the better the control; however, high concentrations of calcium can cause foliar burn.

Do not concentrate CaCl2 (77% flakes) beyond 5 kg/1,000 L of water in mid-July and no more than 7 kg/1,000 L for applications at or beyond mid-August. Do not apply calcium formulations that contain nitrogen after the end of July or fruit quality and storability may suffer. For all formulations, consult the label directions for concentrations and compatibility with pesticides. The product used is not as important as the total amount of actual or elemental calcium applied. For example, calcium chloride (77% flakes) contains 28% actual calcium. For acceptable results, up to 12 kg/ha of actual calcium is often required in a total of four or more sprays.

Calcium sprays may cause foliage and/or fruit injury if applied when low temperature and wet weather delay drying of the spray. Injury can also occur if calcium is applied in hot (over 25°C) or humid weather.

Recent studies with calcium sprays on McIntosh failed to show an advantage in fruit firmness and storage quality when fruit was stored in regular controlled atmosphere storage for five and a half months. Limit applications of calcium to fruit that has a known deficiency and/or is prone to bitter pit or cork spot. For more information on calcium disorders, consult OMAFRA Factsheet, Bitter Pit Control in Apples, Order No. 00-009.

Table 4-5. Calcium Foliar Sprays (PDF 233 kb)

* When using calcium chloride, mix required calcium in a pail of water first to be sure all product is dissolved before adding slurry to spray tank.

Magnesium (Mg)

Magnesium soil test values between 100–250 ppm are considered adequate when you plant fruit trees. Magnesium deficiency has become more evident in orchards, particularly where high rates of potash have been used. Magnesium deficiency can lead to premature drop of fruit at harvest, especially with McIntosh. As magnesium is a part of the chlorophyll molecule, magnesium deficient trees have older leaves that are pale in colour. Leaf analysis is the best way to evaluate magnesium requirements.

Foliar sprays of magnesium effectively correct this deficiency for the current year only. See Table 4-6. Magnesium Foliar Sprays.

Table 4-6. Magnesium Foliar Sprays (PDF 105 kb)

Timing	Product	Rate	Notes
Three sprays spaced two weeks apart beginning at calyx	Magnesium sulfate (epsom salts)	20 kg/1,000 L water	Wet tree to point of runoff. Do not concentrate beyond 40 kg/1,000 L water.
	Liquid formulations including chelates*	Consult product label	May be compatible with some pesticides. Consult product label.