Orchard Nutrition

Good orchard fertilizer practices and proper tree nutrition are extremely important for satisfactory yields and quality apples. Soil and foliar analysis plus orchard observation should be used to determine the nutritional status of the tree. One of the most effective nutrient management practices in an apple orchard is the maintenance of the soil pH in the range of 6.0 for the subsoil to 6.5 for the topsoil because the pH influences the availability of the various elements to the plant. Figure 1 shows the availability of some essential nutrient elements as influenced by the soil pH. For example, as the soil pH becomes acidic (pH <5.5), the phosphorous in the soil becomes unavailable to the plant. It does not matter if there is an adequate amount of phosphorous in the soil; the roots are unable to uptake it.

Under common orchard practices, the soil tends to become more acidic over time, and a regular liming program is required to maintain the soil at the proper pH. Table 1 lists the commonly used nitrogen fertilizers and their residual effect on pH. Soil pH and texture are commonly used to determine the lime requirements. Leaf tissue analyses indicate the amounts of the various elements that have been taken by the tree and translocated to the foliage. In other words, soil analysis tests gives you an assessment of acidity and fertility of the soil before the growing season, and leaf analysis gives you the nutritional status of the plant during the growing season. Soil and leaf testing is available through UVM Agricultural and Environmental Testing Laboratory.

Knowing the leaf analysis standards for apple, your soil and leaf analysis results, and personal, visual observations should help you make decisions in determining what nutrients are causing an unwanted response, and what treatments are necessary to change or enhance the response. Due to the many variables involved, such as cultivar, rootstock, soil pH and type, age of tree, the grower is the only person should make the final call on tree fertilization. Table 2, with minor modifications, was compiled by D. Schmitt and J. Clements, under the supervision of Dr. Costante in 1993. It is an attempt to familiarize you with information regarding the role of macro and micro nutrients, nutrient disorder symptoms, and corrective measures. This information has been adapted from several publications, particularly useful was the Orchard Nutrition Management by W. C. Stiles and W. S. Reed from Cornell Cooperative Extension. Tables 3 and 4 are the leaf analysis standards and the fertilizer chart recommendations, respectively, for young- nonbearing trees. These tables are intended only as general guides to maintain tree nutrition at an optimum level rather than correcting severe deficiencies

Nutrition pointers

  1. Adding too much fertilizer is not only a waste of money, but it can have a negative impact on the plant and fruit. In apples, too much nitrogen results in soft fruit with poor color. Too much potassium can cause Bitter Pit.
  2. The amount of nitrogen applied is more important to fruit quality than its form. Use the cheapest source available.
  3. The relationship between nitrogen and potassium is very important. A ratio on N/K of about 1.25 is about where the balance of these two elements results in optimum fruit size, color, sugar content and firmness.
  4. Foliar sprays should be considered as supplemental treatments. They add usually no more than 15% of the tree's nutritional needs. If you have had Bitter Pit or Cork Spot, regular applications of calcium chloride are recommended.
  5. Apply ground fertilizers early in the spring, one or two weeks before bloom.

Care of young trees 

  1. Special attention should be given to phosphorous fertilization at pre-plant site preparations. Surface applications of phosphates in established orchards are likely to contribute to surface water contamination.
  2. Young trees can be fertilized by a split application in early April and early June.
  3. Try to band in a circle 12 to 18 inches from the trunk. A leaf analysis program should begin a year before the trees will produce a commercial crop.

 

 Fig. 1. Availability of some essential nutrient elements as influenced by soil acidity or alkalinity

 

pH

 

Table 1. Nitrogen FERTILIZERS, their COMPOSITION, and RESIDUAL EFFECT on pH

Inorganic

%Nitrogen

% Other elements

Residual effect

Anhydrous ammonia

82

----

acid

Urea

45

----

acid

Ammonium nitrate

33.5

----

acid

Calcium nitrate

15.5

19 Ca

basic

Potassium nitrate

13

44 K2O

basic

Organic

 

 

 

Dried blood

15

1.30 P2O5; 0.70 K2O

acid

Activated sludge

5.00

3.00 P2O5

acid

Cottonseed meal

3.15

1.25 P2O5;1.15 K2O

acid

 

Table 2. 1998 Apple Team Mineral Nutrition Bearing Orchard Fertilization Summary  

NUTRIENT

PHYSIOLOGY

IDEAL FOLIAGE RANGE

DEFICIENCY

Capitalized nutrients- the 'big five', are of particular importance for tree maintenance and fruit quality

An appreciation for the complex physiological role played by mineral nutrients helps explain their importance in orchard nutrition

Leaf analysis results in this range should be considered ideal for maintaining tree health, adequate vigor, and fruit quality

Deficiency symptoms are important indicators of a nutrient deficiency or imbalance

NITROGEN (N)

Primary building block for all plant parts- leaves, shoots, roots, fruit buds etc.

Young, non-bearing trees 2.4 to 2.6%; young, bearing 2.2-2.4%; mature, soft fruit 1.8 to 2.2%; mature, hard and processing 2.2-2.4%

Older leaves affected first. Leaves are small, uniformly light green or yellowish. Tips and margins may show necrosis. Bark is yellowish orange. Shoots/spurs-short, thin and spindly. Fruit set may be reduced. Current season's growth <4"

POTASSIUM (K)

Enzyme activator, necessary for the formation and translocation of sugars, proteins, plant growth hormones

1.35 to 1.85%

Older leaves affected first, necrosis advancing from margins toward mid-rib; slender shoots and weak spurs; more susceptible to winter injury; smaller, poorly colored, low acidity fruit

CALCIUM (Ca)

Component of cell wall; regulates nutrient uptake and movement in plant

1.3 to 2.0 %

Deficiency symptoms difficult to identify in leaves. Shoot and root growth inhibited; storage disorders-bitter pit, cork spot, internal breakdown

MAGNESIUM (Mg)

Molecular component of chlorophyll ; enzyme activator

0.35 to 0.50

Older and mid-shoot leaves, and those on spurs bearing fruit are affected first. yellow-brown necrotic areas; shoots and spurs are thin, weak, and brittle; blind wood and premature fruit drop

BORON (B)

Aids in formation of pollen tube and feeder roots, and translocation of Ca, sugars, plant hormones

27 to 45 ppm

Flower development and fruit set decreased; young leaves often small, misshapen; corkiness in fruit flesh, wrinkled skin

Phosphorous (P)

Cellular energy transfer and storage; nucleic acid component or regulator cofactor

0.13 to 0.33%

Deficiencies generally not seen in fruit trees. New leaves are small, bluish green, margins or main veins or undersides of leaves having purple pigmentation. Older leaves drop early. Flowering is reduced. Affects fruit quality

Zinc (Zn)

Component or regulator cofactor of enzymes, plant hormones proteins (i.e.. aids in normal growth and fruiting)

35 to 50 ppm

Leaves at shoot tip are stunted and misshapen with mottled necrosis; little leaf disease; leaf rosettes may be confused with winter injury; reduced fruit set and, quality, and size

Manganese (Mn)

Aids in chlorophyll synthesis; involved in photosynthetic oxygen evolution

50 to 150 ppm

Older and mid-shoot leaves affected first. ' Herringbone' chlorosis between main veins. Shoot dieback may occur. Flowering and fruit set are reduced

Iron (Fe)

Required for chlorophyll formation; a chlorplast enzyme component

50+ ppm

Chlorosis of tip leaves while veins remain green. Shoot growth is stunted and may die back.

Copper (Cu)

Important enzyme component

7 to 12 ppm

Younger leaves are affected first. Leaves are stunted or misshapen with irregular margins. Whitish, mottled chlorosis between veins. Fruit color, quality, and size are affected


Table 2. (cont.)1998 Apple Team Mineral Nutrition Bearing Orchard Fertilization Summary  

NUTRIENT

EXCESS

FOLIAR APPLICATION

GROUND APPLICATION

COMMENTS

Capitalized nutrients- the 'big five', are of particular importance for tree maintenance and fruit quality

If an element is in excess in soil or plant tissues, expect to see the following- often debilitating, toxicity symptoms

Most/foliar sprays are 'quick-fix' solutions to nutrient deficiencies that supplement ground applications

The preventive approach to orchard nutrition- a ground fertilization program based on soil and leaf analysis results

Be sure to consult an orchard nutrition reference or your extension fruit specialist for more detail

NITROGEN (N)

Excessive shoot growth; soft, green fruit (poor CA storage candidate); more susceptible to winter injury and diseases such as fireblight

Urea @ 9#/acre, IX-3X; apply at pink and 1st cover; boosts spur vigor; do not apply with oil

Ammonium nitrate (34-0-0) @ 0-75#/acre (see comments)

See Table 1 for N fertilizer details. In bearing trees, a rule of thumb for applying actual N on a per tree basis would be: 8-15 bushels: 0.66 lb; 15-25bushels :0.66-1.0 lb; >25bushels: 1.33-2.0 lb;

POTASSIUM (K)

Mg, and Ca deficiencies become pronounced w/ excess K

None

Muriate of potash (0-0-60) @ app. l50-200 #/Ac annually; if Mg low use Sul-Po-Mg

Potassium deficiencies are more common with heavy crop loads, high N and inadequate water supply; annual fertilization advisable

CALCIUM (Ca)

No distinctive symptoms

CaCl @ 1-4 # / 100 gal, in 4-6 sprays 14 days apart, begin 7-10 days after petal fall

lime 4 tons/Ac every 4-5 years or as indicated by soil test; if low in Mg use dolomitic lime

Sprays necessary to offset fruit quality problems, however, maintain soil calcium supply via liming. Fluctuations in soil moisture increase severity of deficiency symptoms

MAGNESIUM (Mg)

Can hinder Ca uptake (Ca deficiency symptoms become more prevalent) when soil Ca supply is low

Epsom salts @ 15 # /Ac @ PF, 1st and 2nd covers; generally tank-mix compatible

Dolomitic (high Mg lime) @ 4 tons /Ac every 4-5 years

Supplement ground application w/foliar sprays; if K high, Mg requirement increases. Deficiencies more pronounced in young trees or trees with heavy crop loads.

BORON (B)

Chlorosis of leaf tissue along the midrib. Premature defoliation from shoot tip toward base. Fruit drop likely; fruit cracking. Excess symptoms similar to deficiency.

Prebloom to bloom (if leaf sample< 35ppm)- Solubor @0.5-1.0/100 gal; at PF or 1st-3rd cover sprays Solubor at 1lb/100 gal not compatible with oils, EC's

Granular Borate 2-3# (young trees) up to 7-8 # (older trees)/Ac often blended w/ other fertilizers

Foliar and ground applications should be used to supplement one another. Deficiencies more pronounced in trees with heavy crop loads or under dry weather conditions

Phosphorous (P)

Zn and Cu deficiencies exacerbated

No application necessary

Superphosphate (0-20-0)or triple superphosphate (0-45-0) to maintain soil levels at 300-400 # / Ac

P fertilization of bearing orchards usually not necessary; pre-plant P in root zone very desirable

Zinc (Zn)

Cu deficiency symptoms induced

Zn sulfate @(22-36 % Zn); apply 3-5 # actual Zn/ 100 gal. Dilute only, up to silver tip

Trees generally unresponsive to ground applications

Maintain pH of 6.0-6.5 to reduce likelihood of Zn deficiency

Manganese (Mn)

Necrotic bark tissue (measles on Delicious; otherwise not evident

Mn sulfate @ 2-4 # / 100 gal. 1 week before PF; EDBC fungicides also contain Mn

None

Delicious most sensitive to excess Mn; toxicity symptoms commonly associated w/Ca deficiency

Iron (Fe)

None

None

None

Maintain soil pH at 6-6.5 to avoid Fe deficiency problems

Copper (Cu)

Root death; other micronutrients likely to become exaggerated

Choose bordeaux mixture or other Cu containing fungicide for disease control (i.e.. Fireblight, scab if warranted

None for bearing orchards; pre-plant incorporation of Cu sulfate (90-120# Cu /Ac)

Treat foliar application of Cu with caution, as fruit russeting and/or foliage injury likely

 

Table 3. LEAF ANALYSIS STANDARDS FOR YOUNG, NON BEARING APPLE TREES

  Element Optimum

(Within)

Excess

(More than)

Optimum

(Within)

Excess

(More than)

 Nitrogen(N)

2.00 %

2.00-2.50 %

2.50%

Potassium (K)

1.00 %

1.20-1.50 %

1.50 %

Calcium (Ca)

1.00 %

1.25-1.80 %

?

Magnesium (Mg)

0.20 %

0.25-0.40 %

0.50 %

Manganese (Mn)

20 ppm

25-100 ppm

110 ppm

Boron (B)

25 ppm

30-45 ppm

70 ppm

Copper (Cu)

4 ppm

7-12 ppm

12 ppm

Zinc (Zn)

15 ppm

25-50 ppm

50 ppm

 

 

Table 4. YOUNG TREE FERTILIZER RECOMMENDATION CHART

Pounds applied per tree in early spring and 6 to 7 weeks later

Age (yrs)

Calcium nitrate

(15%)

Ammonium nitrate (34%)

Urea (44%)

20-20-20

Muriate/Potash (60%)

Spring

6wks

Spring

6wks

Spring

6wks

Spring

6wks

Spring

6wks

1

1.33

1.33

----

----

----

----

0.50

0.50

----

----

2

1.75

1.75

1.00

1.00

0.75

0.75

1.66

1.66

0.50

0.50

3

2.66

2.66

1.25

1.25

1.00

1.00

2.25

2.25

0.50

0.50

4

3.75

3.75

1.66

1.66

1.25

1.25

3.0

3.0

0.75

0.75

5

4.00

4.00

1.75

1.75

1.33

1.33

3.0

3.0

0.75

0.75


 

Where trade names or commercial products are used for identification, no discrimination is intended and no endorsement is implied. Always read the label before using any pesticide. The label is the legal document for the product use. Disregard any information in this newsletter if it is in conflict with the label.