Table of Contents

Tender Fruit Nutition

Test the soil a year in advance of planting fruit trees, or two years before planting if pH adjustment may be necessary. Some soil amendments do not move readily through the soil profile, but are needed to optimize orchard productivity. These materials include organic matter, phosphorus, potassium, and lime to adjust soil pH. The only opportunity to thoroughly incorporate these materials is before planting.

Manure for Orchards

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 years after application. 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 may make trees more susceptible to winter injury. Observe the following guidelines to receive the benefits of manure while minimizing potential problems:

pH Requirements

The pH of a soil is a measure of its acidity and affects nutrient uptake and crop performance. If the soil test report recommends a lime application to increase soil pH, add lime at recommended rates prior to planting. For details regarding rates and suggested types of lime to use, refer to Soil pH and Liming.

In established orchards, sample soil in the tree row every three years to ensure the pH is satisfactory. If the pH drops below 5.6 on sandy soils or below 5.1 on clay loam soils, apply lime to the sod cover in the fall or before spring cultivation. The results will not be immediate because lime moves and reacts slowly in the soil.

For details regarding suggested rates and types of lime, consult Soil pH and Liming.

Leaf Analysis

In established plantings, leaf analysis is the best method to determine nutrient status of the trees. When used in conjunction with soil analysis, it provides good information for adjusting fertilizer rates. For more information on these tests, see Plant tissue analysis.

Nutrient uptake is affected by many orchard conditions and varies slightly from year to year, depending on the season. For optimum growth and fruit quality, all nutrients must be available in sufficient concentrations. See Table 7-1. Nutrient Concentration Sufficiency Ranges for Tender Fruits.

For leaf analysis to be most effective, sample the same trees each year. Use leaf analysis together with soil test results to make adjustments to the fertilizer program. Fertilizer requirements are adjusted to soil management practices, tree age, rootstock, soil type and previous fertilizer applications. Growth, fruit size, colour and storage quality must also be considered to determine the fertilizer required. See OMAFRA factsheet No.91-012, Leaf Analyses for Fruit Crop Nutrition.

* Leaf nitrogen in non-bearing trees should be 0.2% higher.

Fertilizer for Tender Fruit

Fertilizer for non-bearing tender fruit

The best time to effectively incorporate nutrients such as phosphorus, potassium, boron and lime is before planting. Adequate nutrient levels in the topsoil for orchard establishment are 12-20 ppm phosphorus, 120-150 ppm potassium, 100-250 ppm magnesium and 1,000-5,000 ppm calcium. Table 7-2. Phosphorus and Potassium Soil Requirements Before Planting Tender Fruit Trees, provides information on fertilizer rates prior to planting. Along with the incorporation of organic matter, these fertility levels will sustain the tree in the juvenile years. On coarse-textured, infertile soils, use a starter solution at planting time such as 10-52-10 or 20-20-20. High nitrogen levels can result in excessive growth and incomplete tree hardening. Use cover crops to reduce late season nitrogen levels 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 tree growth. On young trees, broadcast the fertilizer under the spread of the branches. Keep the fertilizer at least 15 cm from the trunk, since injury can occur if it is placed too close.

Fertilizer for bearing tender fruit trees

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

Nitrogen (N)

Nitrogen is necessary for many tree functions, which include growth, fruit bud formation, fruit set and fruit size. Cultivars differ in nitrogen requirements. A cultivar grown for processing could receive more nitrogen than one for the fresh market. In situations where fruit tends to be small, more nitrogen may be needed. Rootstocks, spacing and pruning also affect nitrogen requirements. Tree growth, fruit colour and storability are also important considerations. Because of complex interactions with nitrogen and quality and production, the best guide for nitrogen rates is leaf analysis.

For pear, peach, plum and cherry orchards where leaf analysis is not available, the following rates are considered normal. For each year of tree's age, apply between 30-40 grams of nitrogen. Thus, a five year old tree in sod culture requires 150-200 g of nitrogen. See Table 7-3. Actual Nitrogen Rates per Tree in Sod Culture. The rate for cultivated orchards can be reduced by half as competition for nutrients is greatly reduced. Trees on dwarfing rootstock generally require more nitrogen per ha (not per tree) than trees on more vigorous stocks. When the tree canopy has covered the space available, nitrogen fertilizer requirements level out and do not increase with tree age. Again leaf analysis is the most reliable guide. There are several forms of nitrogen available. Do not apply urea (46-0 0) to orchards with sod between the rows because urea must be incorporated to prevent loss by volatilization. For all tree fruits, do not exceed 200 kg actual nitrogen per ha per year, even in cases of severe deficiency. Late or excessive applications of nitrogen result in poor fruit colour and quality. Available nitrogen late in the season encourages the tree to grow instead of harden off, which potentially leads to winter injury. In cultivated orchards, use cover crops to help lower the nitrogen level in the latter part of the season. Cover crops such as Italian ryegrass, sown about July 1, will take up much of the available nitrogen in the soil and limit tree growth. In orchards with herbicide-treated strips under trees, allow some weed growth late in the season. Weeds take up extra nitrogen, which helps to harden off trees and improve fruit quality. If pruning is to be severe, reduce nitrogen rates or eliminate it for a year. During dry springs, irrigate to move the fertilizer into the rooting zone of the soil just before first bloom or immediately after petal fall. For fire blight-sensitive pear cultivars, use less than the maximum rate of nitrogen suggested.

Nitrogen placement and timing

Apply nitrogen fertilizer in early April. In cultivated orchards, broadcast nitrogen under the tree canopy. In sod orchards, place the nitrogen in a band under the drip line or in the herbicide strip. If there is evidence of fruit bud damage due to severe winter temperatures, it may be necessary to split nitrogen applications. Apply the first application in mid-April and the second, if necessary, after bloom in late May.

Foliar application of nitrogen

When weather or crop conditions create a need for additional nitrogen at a critical time, foliar applications of urea (46% nitrogen) have been successfully used on fruit trees. Late applications adversely affect fruit quality and winter survival of the tree.
Do not rely on foliar sprays to completely substitute for soil applications if nitrogen is required. Make applications based on tree performance and leaf analysis.

Phosphorus (P)

Phosphorus is not required in large amounts by fruit trees. With a few exceptions, the level of phosphorus in Ontario soils is adequate. Phosphorus may be required for sod or cover crop maintenance. A soil test is the best way to determine if the sod needs this nutrient.

If indicated by a soil test, apply phosphorus before planting an orchard when it can be thoroughly incorporated into the soil. Phosphorus soil test values between 12-20 ppm are considered adequate for tree establishment and fruit production.

Potassium (K)

Potassium is important for fruit colour, winter hardiness, tree growth and resistance to disease, such as fire blight in pears. Excess potassium can lead to magnesium (Mg) deficiency, so avoid unnecessary application of potassium. Soil test values between 120-150 ppm are 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, the following rates are considered normal.

Placement and timing

In early spring, apply potassium separately or combined with nitrogen. Some growers make fall applications because of time constraints in the spring. Leaching during winter may cause the loss of some potassium. For this reason, apply in spring if possible. In orchards with sod between the rows, apply potash in a band around the drip line or in the herbicide strip.

Foliar application of potassium

In dry growing seasons, potassium is not readily available to the plant. Foliar applications of potassium may be used where potassium deficiency is confirmed by leaf analysis.

Magnesium (Mg)

Magnesium deficiency has become more evident in orchards, particularly when high rates of potassium are used. Magnesium deficiency can lead to premature drop of fruit.

As magnesium is a part of the chlorophyll molecule, trees deficient in magnesium have older leaves that are pale in colour. Leaf analysis is the best way to evaluate magnesium needs.

Foliar sprays of magnesium are effective to correct magnesium deficiency for the current year only. For longer term correction, soil applications of magnesium are required. Magnesium soil test values between 100-250 ppm are considered adequate when planting fruit trees. See Table 7-4. Magnesium Foliar Sprays.

Do not mix pesticides with magnesium sulfate (Epsom salts) as foliar injury may result. Check the manufacturer's label in regard to the mixture of magnesium chelates with pesticides. Use only chelates recommended for foliar sprays. For long-term corrections, apply magnesium to the soil. The response is not immediate. On some soil types a single early spring application of soil-applied magnesium is not sufficient and a second or third application the following spring may be required before the magnesium level in the tree improves. To be sure that fruit drop is not a problem during this period, apply foliar sprays for the first two years in addition to soil applications. For soil corrections, apply 5-7 kg per mature standard tree and 3-4 kg per mature dwarf tree of sulphate of potash magnesia. This is a granular fertilizer known by several trade names. It contains approximately 21% potash and 11% magnesium. Apply in early spring in a band under the tree drip line. It contains potassium (K) and the rate of application depends on potash needs. No further potash is likely to be required, but apply nitrogen at recommended rates. Other sources of magnesium also work well as a soil application. If magnesium is being blended with the fertilizer, apply at least 80 kg of available magnesium per ha when the fertilizer is spread. Use dolomitic limestone on acidic soils to raise the soil pH and to supply magnesium.

* Use chelates recommended for foliar sprays.

Calcium (Ca)

Lack of calcium is associated with fruit quality problems in pear and gummosis in European plums and prunes. Calcium sprays must contact the fruit for uptake to be effective; therefore water volumes capable of wetting the entire tree are required. Some formulations of calcium chloride (CaCl₂) result in poor fruit finish if applied too close to harvest. Excessive calcium can cause foliar damage. The product used is not as important as the total amount of actual (elemental) calcium applied.

Use CaCl₂ (77% flakes) at 4 kg/1,000 L of water from early July to mid-August. Apply three sprays, 10-12 days apart. 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 injure foliage and fruit if applied during low temperatures and wet weather. These conditions delay the drying of the spray. Injury can also occur if calcium is applied in hot (over 25°C) or humid weather. Do not apply calcium formulations containing nitrogen after the end of July or fruit quality and storability may suffer. For all formulations, consult the label for rates and compatibility with pesticides.

Micronutrients for Tender Fruit

Deficiencies of micronutrients or trace elements are not widespread in Ontario fruit plantings. The desirable range for micronutrients is quite narrow. Micronutrients applied in excess can cause more damage than deficiencies. Leaf analysis is more effective than soil analysis to evaluate tree micronutrient status. For more information see Micronutrients.

Warning: Apply nutrient sprays according to recommended rates on the product label. Do not spray during temperatures above 25°C.

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