Nutrient Management of Apple Orchards
Contents
Characteristics of Commonly Available Fertilizers
When developing mineral nutrient management programs for tree fruits, it is important to consider the nutrient demand-supply relationship throughout the season.
Early season canopy development and fruit growth require large amounts of nitrogen (N), while fruit quality development and the acquisition of adequate cold hardiness by the tree later in the season require only a minimum supply of N. Thus, an ideal seasonal pattern of tree nitrogen status should be to start the season with relatively high nitrogen status to promote rapid leaf development and early fruit growth. As the season progresses, nitrogen status should decline gradually to guarantee fruit quality development and wood maturity before the onset of winter. There are three sources of nitrogen supply tree fruits can use. First is reserve nitrogen that has accumulated in the tree from the previous growing season. This source of nitrogen is readily available for initial growth during the spring. In fact, spur leaf development and early fruit growth are mainly supported by the reserve N. The second source is the natural N supply from the soil mineralization process. This process provides substantial amounts of nitrogen for trees growing on soils with high organic matter. The third is nitrogen fertilizers applied to the soil or to the foliage. To determine the amount of fertilizer nitrogen needed, we need to know the total tree demand and the amounts the other two nitrogen sources can provide. However, there is not enough information currently available on this demand-supply relationship to make this approach practical. Instead, soil and leaf analyses have been developed over the years to help growers diagnose tree nutrient status and soil nutrient availability and make adjustments on their fertilization programs accordingly.
Soil analysis is very useful for determining lime requirement and mineral availability in the soil before orchard establishment. For existing orchards, it provides information necessary for interpreting leaf analysis results and modifying fertilization programs.
A soil nutrient analysis should be performed before planting a new orchard and every 2 to 3 years after orchard establishment. The soil sample taken should be representative of the soil type and conditions within the orchard. Generally, the area included in any one-sample collection should not exceed 10 acres. Scrape away the surface 1-inch of soil, then collect samples from the 1 to 8 inch depth, and separate samples from 8 to 16 inches. In a 10 acre orchard, a minimum of 10 to 20 subsamples is suggested. Thoroughly mix the 1-8 inch subsamples together to provide a representative sample for the topsoil, and treat the 8 to 16 inch subsamples similarly to get a representative sample for subsoil. Soil samples can be sent to Cornell Nutrient Analysis Lab, 804 Bradfield Hall, Cornell University, Ithaca, NY 14853, Phone 607-255-4540, Fax 607-255-7656.
New York soils are classified into 5 management groups on the basis of texture and parental materials. Percentage of clay, buffering capacity, and potassium supply power decrease from group I to V.
Table 19. Soil management groups
|
Soil group |
Texture |
Examples |
|
Clayey soils, fine-textured soils. |
Vergennes, Kingsbury, Hudson, Rhinebeck, Schoharie, Odessa. |
|
|
II |
Silty loam soils with medium to moderately fine texture. |
Cazenovia, Hilton, Honeoye, Lima, Ontario, Lansing, Mohawk, Chagrin, Teel. |
|
Silty loam soils with moderately coarse texture. |
Barbour, Chenango, Palmyra, Tioga, Mardin, Langfor, Tunkhannock. |
|
|
Loamy soils, coarse- to medium-textured soils. |
Bombay, Broadalbin, Copake, Empeyville, Madrid, Sodus, Worth. |
|
|
Sandy soils, very coarse-textured soils. |
Alton, Colton, Windsor, Colonie, Elmwood, Junius, Suncook. |
pH values of orchard soils should be maintained in the range of 6.0 to 6.5 throughout the soil profile to optimize plant growth and nutrient availability. For preplant soil preparation, we recommend the pH of topsoil (0–8 inch depth) be adjusted to 7.0 and that of subsoil to 6.5. Most soils in New York have pH values lower than optimum and need liming to raise the pH prior to planting a new orchard. This also ensures adequate calcium and magnesium supplies in the soil.
The amount of lime required to adjust topsoil pH to 7.0 and subsoil pH to 6.5 is determined by the current pH values of the topsoil and subsoil (determined from a soil analysis) and the buffering capacity of the soil, i.e. exchange acidity or cation exchange capacity, (CEC), of topsoil and subsoil (also determined from a soil analysis). Using these values, the lime requirement can be determined from Table 20 for topsoil and from Table 21 for subsoil. The amount of lime to be added is the sum of topsoil plus subsoil requirement. When complete soil tests are not available, Table 22 may be used to estimate lime requirement.
The lime recommendations in Tables 20, 21 and 22 are for 100% effective neutralizing value. The actual lime rate to be applied is calculated by dividing the recommended 100% ENV rate by the ENV of the lime to be used.
The desired levels of soil calcium and magnesium are listed in Table 23 for different soil management groups. If soil magnesium levels are below the desired level, then high-Mag lime should be used for liming.
Lime should be thoroughly harrowed into the surface soil, then plowed to work it as deeply as possible into the soil. If large amounts of lime are required, split application is recommended, working one-half or two thirds of the total amount of lime into the soil as indicated above, plus thoroughly harrowing the remainder into the topsoil after plowing.
Table 22. General lime recommendations for a depth of 16 inches (tons of 100% ENV lime per acre)
2. Other Preplant Nutrients
Potassium: The desired levels of soil potassium are listed in Table 23 for the different soil management groups. The difference between the desired level and the soil test result in both the topsoil and the subsoil is the amount to be added to the soil. [(Desired Level topsoil – actual level topsoil) +(Desired Level subsoil – actual level subsoil) = lb./acre K2O per 16-inch depth.
Phosphorus: Incorporation of appropriate rates of phosphorus during preplant soil preparation is the best means of providing adequate phosphorus for the life time of the orchard. The recommended amounts of preplant phosphorus for various soil test levels are listed in Table 24. The amount of phosphorus to be added is the sum of topsoil plus subsoil requirement.
Nitrogen: During preplant soil preparation, an application of nitrogen at 40 lb./acre is suggested for cover crop establishment. An additional 40 lb./acre is suggested when the cover crop is plowed down or when seeding the permanent grass sod.
Boron: Typical boron levels for different soil textures are given in Table 25. If soil test shows boron levels are in the low to medium range, then 2 to 3 lb. of boron is recommended for preplant soil preparation.
|
Soil Group |
CEC (me/100g |
Ca (lb./acre) |
Mg (lb./acre) |
K2O (lb./acre) |
|||||||
|
topsoil |
subsoil |
topsoil |
subsoil |
topsoil |
subsoil |
topsoil |
subsoil |
||||
|
25 |
17 |
7800 |
4600 |
950 |
550 |
520 |
300 |
||||
|
II |
20 |
13 |
6200 |
3700 |
750 |
450 |
450 |
260 |
|||
|
III |
18 |
12 |
5600 |
3300 |
700 |
400 |
430 |
250 |
|||
|
IV |
16 |
11 |
5000 |
2900 |
600 |
350 |
400 |
240 |
|||
|
V |
12 |
8 |
3700 |
2200 |
450 |
250 |
330 |
200 |
|||
Table 24. Soil test phosphorus values and rates of phosphate (P2O5) application for orchards
|
Soil test value P (lb./acre) |
Amount of P2O5 to apply (lb./acre) |
|
|
|
Pre-planting |
Established orchards* |
|
<1 |
120 |
60 |
|
1-3 |
100 |
60 |
|
4-8 |
60 |
30 |
|
>9 |
40 |
0 |
|
* Do not apply phosphate to established orchards unless leaf analysis also indicates a need. |
||
Table 25. Boron soil test levels for soils with different textures
|
Relative Soil Test Levels |
Loamy Sand |
Sandy Loam |
Loam & Silt |
Rate of boron (lb./a ) |
|
Very High |
>0.60
ppm |
>0.90
ppm |
>1.20
ppm |
0 |
|
High |
0.36-0.60
ppm |
0.61-0.90
ppm |
0.81-1.20
ppm |
1 |
|
Medium |
0.20-0.35
ppm |
0.30-0.60
ppm |
0.40-0.80
ppm |
2 |
|
Low |
<0.20
ppm |
<0.30
ppm |
<0.40
ppm |
3 |
Note: Soil test results for boron should be judged in relation to leaf analysis results. Leaf analysis is considered to be a better indicator of boron status.
Fertilization Program for Young Trees
When new trees are planted in the spring, immediate supply of adequate water is essential to settle the soil around the roots, but application of nitrogen fertilizer is not recommended. This is because the initial tree growth is mainly supported by the nutrient reserves within the tree and the uptake of nutrients from the soil is often delayed due to the damaged root system. In addition, applying large amounts of dry fertilizers at planting may cause damage to the roots. The first application of nitrogen fertilizer should be made at budbreak. Applying weekly liquid fertilizers through a drip irrigation system (fertigation) is the most efficient and effective method of application. This is especially true with large feathered trees which do not have an adequate root system to support the tree and thus show a very large improvement with fertigation. Apply 0.5 ounces per tree per week for 8 weeks or alternatively apply 100 ppm N in all water applied through the drip system over the first 8 weeks. If fertigation is not possible then soil applied liquid nitrogen fertilizers are preferred beginning at bud break at a rate of 0.6 to 1.0 ounce of actual nitrogen per tree. If dry fertilizers have to be used, make sure to avoid any contact with the trunk. Apply a second soil application at the same rate 4 weeks after budbreak. To improve early season tree growth, 2 to 3 sprays of 6 lbs of urea per 100-gal water is recommended at 10 to 14-day intervals beginning at 3 weeks after budbreak. In early October, 2 sprays of foliar urea at 25 lbs per 100 gal are also suggested.
In the second year, when new shoots begin their rapid growth (early to mid-May), continue fertigation with 100ppm N or if fertigation is not available then apply 0.1 to 0.2 pounds of actual nitrogen per tree and a similar foliar N spray program as in year 1. If trees have a substantial crop and the variety is susceptible to bitter pit, a foliar calcium program is recommended.
Fertilization Program for Established Orchards
Leaf analysis indicates the concentration of nutrients that are present in the foliage. If leaf samples are taken correctly and the results are interpreted properly, it provides a good tool for developing an effective fertilization program. Leaf analysis standard for fruit trees are listed in Table 26.
Table 26. Leaf analysis standards for tree fruits (dry weight basis).
|
Element |
Crop |
Desired level |
|
Nitrogen |
Young nonbearing apples and pears Young bearing apples and pears Mature soft apples and pears Mature hard apples and processing Cherries, plums, prunes Peaches |
2.4-2.6% 2.2-2.4% 1.8-2.2% 2.2-2.4% 2.4-3.4% 3.0-4.0% |
|
Phosphorus Potassium Calcium Magnesium |
All crops All crops All crops Apples and pears Stone fruits |
0.13-0.33% 1.35-1.85% 1.3-2.0% 0.35-0.50% 0.40-0.60% |
|
Boron
Zinc Copper Manganese Iron |
Apples and pears Stone fruits All crops All crops All crops All crops |
35-50 ppm 30-40 ppm 30-50 ppm 7-12 ppm 50-150 ppm 50+ ppm |
Leaf samples should be collected between 60 to 70 days after petal fall, which generally corresponds to late July and early August. Mid-shoot leaves should be sampled from current season terminal shoots on the periphery of the tree. Sample trees should represent the general conditions of the orchard in terms of vigor, crop load, etc. Each sample should consist of about 100 leaves collected from several trees in the area being sampled. Do not mix leaves from different varieties, soil conditions, tree vigor, or crop load. Record observations on terminal shoot length, thickness, crop load, and fruit size. Leaf samples can be sent to: Cornell Nutrient Analysis Lab, 804 Bradfield Hall, Cornell University, Ithaca, NY 14853, Phone 607-255-4540, Fax 607-255-7656.
It should be recognized that leaf analysis has its limitations. First, leaf samples are taken relatively late in the growing season. Even if you can get the leaf analysis results back immediately, you may not have enough time left during the season to correct mineral deficiencies if there are any. Secondly, routine leaf analysis cannot detect the transient nutrient demand by certain physiological processes early in the season. For example, trees have a large transient demand for boron at bloom. Finally, even if leaf analysis shows no mineral nutrient deficiency, you still need to have a maintenance program in place to replace the amount of nutrients that is lost in harvested fruit and fallen leaves every year. Therefore, two fertilization programs are suggested here for established trees. One is a maintenance program. The other is a corrective program for trees with nutrient deficiency.
1. Maintenance program: This program is suggested when leaf analysis shows no nutrient deficiency or no deficiency symptoms are observed.
|
Timing |
Foliar Sprays |
Ground Applications |
|
Green tip |
One spray of 2 to 4 lbs of a fixed copper product per 100 gal (C-O-C-S or Kocide). |
|
|
Tight cluster to pink |
One spray of tank mixed 3 lbs of urea and 1 lb Solubor/100 gal |
Apply 20 to 40 lbs of actual nitrogen/acre to soil. |
|
Petal fall to early cover sprays |
One spray of Zn-EDTA at label rate at second cover. Plus One spray of 3 to 4 lb of calcium chloride/100 gal at third cover. Plus Two sprays of 10-15 lb of Epsom salt/100 gal at petal fall, and second cover. |
Apply 40 to 60 lbs of potassium/acre to soil at petal fall. |
|
End of shoot growth to harvest |
Three to four sprays of 3 to 4 lbs of calcium chloride/100 gal at 14-day intervals for bitter pit susceptible varieties. |
|
|
After harvest |
|
Apply 40 to 60 lb of potassium/acre to soil. Plus Every 2 to 3 years, apply appropriate amount of lime determined from soil analysis. |
2. Corrective program: This program is suggested when leaf analysis shows nutrient deficiency, or deficiency symptoms are observed. Match fertilizer applications to specific nutrient deficiency.
|
Timing |
Foliar Sprays |
Ground Applications |
|
Green tip |
One spray of 2 to 4 lbs of a fixed copper product per 100 gal (C-O-C-S or Kocide) |
|
|
Prebloom period |
Two sprays of tank-mixed 1 lb of Solubor, 3 lbs of urea, and Zn-EDTA at label rate per 100 gallon, one at 1/2" green and the other at tight cluster to pink |
Apply 40 to 60 lbs of actual nitrogen/acre to soil. |
|
Petal fall to early cover sprays |
Two foliar sprays of 5 lbs of urea/100 gal at petal fall and first cover. Plus Two sprays of Zn-EDTA at label rate at petal fall and second cover. Plus Two foliar sprays of 1 lb of Solubor/100 gal at first and third cover. Plus Three sprays of 10-15 lbs of Epsom salt/100 gal applied at petal fall, first and second covers. Plus One foliar spray of 3 to 4 lbs of calcium chloride per 100 gal at third cover. |
Apply 60 to 150 lbs of Potassium/acre to soil at petal fall. |
|
End of shoot growth to harvest |
Five to six sprays of 3 to 4 lbs of calcium chloride/100 gal at 14-day intervals. |
Apply 60 to 150 lbs of potassium to soil at the end of shoot growth. |
|
After harvest |
Two sprays of 25 lbs of urea/100 gal at 7 to 10-day intervals. Plus One spray of 1 lb of actual copper/acre as copper sulfate. |
Soil application of 60 to 150 lbs of potassium/acre as sulfate of potash-magnesia. Plus Soil application of dolomitic lime to increase calcium and magnesium supply based on soil and leaf analyses.
|
Special Considerations in Foliar Application of Nutrients
To minimize the number of sprays applied in the orchard, it is frequently desirable to combine various nutrient materials or to add them in tank mixes with pesticides. Before doing so, however, one needs to make sure they are compatible.
Generally, urea, Solubor, and Zn-EDTA are compatible. Urea, Solubor, and Zn-EDTA have been used together safely in prebloom sprays on apples and pears. A tank mix of urea and Epsom salts has sometimes injured young apple foliage; if both are required, they should be applied separately. Epsom salts and some of the boron products listed in Table 30 may increase the pH of the tank mix, and if used with pH-sensitive pesticides, pH of the tank mix should be tested and adjusted by using a suitable acidifying agent. Solubor and presumably other forms of boron should not be tank-mixed with any pesticide contained in water-soluble plastic packages because it inhibits the dissolution of the plastic. In general foliar nutrients should not be mixed with oil. Solubor in particular should not be tank-mixed with oil.
Although Epsom salts, Solubor and Zn-EDTA are compatible for use in postbloom sprays, many orchardists prefer not to add all three to one tank. A petal fall spray may then contain Epsom salts alone or with Solubor; the first cover spray a combination of Epsom salts and Solubor; the second cover spray a combination of Epsom salts and Zn-EDTA; and the third cover spray a combination of Solubor and Zn-EDTA.
Calcium chloride may be physically incompatible with Epsom salts, resulting in plugging of sprayer nozzles. Calcium chloride cannot be tank-mixed with Zn-EDTA because some of the dissolved calcium may displace Zn, causing phytotoxicity.
It should be pointed out that some Zn-chelate products contain a large percentage of unchelated Zn, which may cause injury to foliage and fruit. Therefore, before using a new Zn product in your orchard, test the product by spraying a few trees at the label rate to see if any phytotoxicity occurs.
More detailed information concerning nutrient management for orchards can be found in Cornell Cooperative Extension Information Bulletin 219, Orchard Nutrition Management by Warren Stiles and Shaw Reid. See the section on “Tree Fruit Reference Materials” at the end of this publication for ordering information.
Prepared by Lailiang Cheng, Dept. of Horticulture, Ithaca, and Terence Robinson, Dept. of Horticultural Sciences, Geneva.
Characteristics of Commonly
Available Fertilizers
Table 27. Nitrogen fertilizers
|
Common name |
% N |
Pounds per |
Acidity or Basicity (lb CaCO3/lb |
|
|
Acidity |
Basicity |
|||
|
Ammonia, anhydrous |
82 |
1.22 |
1.8 |
— |
|
Ammonia, aqua |
20 |
5.00 |
1.8 |
— |
|
Ammonium nitrate |
33.5 |
2.98 |
1.8 |
— |
|
Ammonium polyphosphate |
12 |
8.33 |
4.1 |
— |
|
Ammonium sulfate |
20.5 |
4.88 |
5.4 |
— |
|
Calcium nitrate |
||||