How to get your tree nutrition right in the 2013 season?
Mario Miranda Sazo, Cultural Practices
Lake Ontario Fruit Program
Work on apple tree nutrition has shown that (1) fruit harvest removes significant amounts of potassium from the orchard every year, (2) sandy or gravel soils have low potassium supply power, (3) NY soils generally have low potassium levels, and (4) low organic matter leads to low potassium supply. Potassium has the highest concentration in fruit and more than two thirds of the total tree K requirement is found in fruit. Apple trees have a constant demand for potassium from bloom to fruit harvest and about 55 to 60 lbs of potassium is removed at a fruit yield of 1000 bushels/acre. This number increases to about 75 to 80 lbs at a fruit yield of 1500 bushels/acre, which is equivalent to about 100 lbs of K2O. Therefore, it is critical to have a maintenance program to make up for the K removed from your orchards even if your soil K levels are adequate. In anticipating a heavy crop this year, the trees will need a significant amount of K. If you use regular ground application, put down the K in the spring if you have not applied any K last fall.
There are two windows for regular soil nitrogen application that would fit the tree nitrogen demand pattern: one is from budbreak (early April) to the beginning of rapid shoot growth (late May) and the other is late season when soil N application no longer affects fruit quality (just before or shortly after fruit harvest). Nitrogen applied early in the season contributes directly to rapid leaf area development (both spurs and shoots), fruit set, and fruit growth in the current season while nitrogen applied late in the fall helps to build up nitrogen reserves. Therefore, soil application of nitrogen between budbreak and petal fall is probably the best way to meet the tree nitrogen demand early in the season. For orchard soils in NY and the Northeast, the amount of fertilizer N required is anywhere between 0 and 80 lbs, which would contribute 0 to 30 lbs of actual nitrogen to the trees, assuming the fertilizer uptake efficiency is between 30 to 40%. If more than 40 lbs actual N per acre is to be applied, a split application, half at a couple weeks after budbreak and the other half at petal fall or shortly thereafter, is recommended. Optimum growth of apple trees is associated with leaf nitrogen values of approximately 1.8 to 2.6 percent depending on tree age, type of fruit, and the intended market. For example, rapid growth of young trees is highly desirable for developing the canopy to capture sunlight for promoting early cropping. The optimum leaf N for young apple trees is approximately 2.4 to 2.6 percent. As trees mature, less vegetative growth is desired and the “satisfactory†level of nitrogen is generally reduced to improve color development and fruit firmness. Consider early foliar N spray for fruit set and early fruit growth when leaf analysis shows less than 2.2 percent leaf N the previous year. Foliar N spray can extend the effective pollination period and promote fruit cell division.
Lime and its benefits: Thorough incorporation of adequate amounts of lime prior to planting a new orchard is essential. The topsoil (0-8 inch depth) should be adjusted to pH 7 and subsoil (8-16 inch depth) to pH 6.5. An adequate liming program based on soil tests should be the first consideration in developing orchard fertilization plans. Lime is the most economical source of calcium and magnesium. Regulation of soil pH through liming is also necessary to achieve optimal response to other nutrient elements.
Placement of lime: Time required for lime to act is influenced by method of placement (i.e. soil contact) and by fineness of the material. In preparing soil before planting a new orchard, maximum benefit is obtained by thoroughly harrowing or rototilling the lime into the surface soil, and then plowing to work it as deeply as possible into the soil. If large quantities of lime are required it should be applied in split applications. Working one-half to two-thirds of the total amount of lime into the soil as indicated above, plus thoroughly harrowing the remainder into the topsoil after plowing, is often suggested as an appropriate method for liming during preplant soil preparation. With some fine-textured soils that require large quantities of lime, application of about two-thirds of the total lime required in such a manner, followed by biennial surface applications of additional lime may be necessary to achieve the desired goal.
Surface applications of lime in established orchards move slowly into the soil and must be considered as long term corrective or maintenance programs. Regularly scheduled applications of lime of 2 tons per acre every two years, as predicted by soil and leaf analysis, represent the best available means of maintaining pH values of 6.0-6.5 and calcium and magnesium supplies in the soil. The type of lime (i.e., calcitic or dolomitic) should be determined by the need for magnesium. In most cases, even if soil magnesium is fairly high, dolomitic lime is suggested for orchards. Dolomitic lime generally has a greater neutralizing value than calcitic lime.
Tree Fruit Nutrition Summary: Fertilizer programs in NY are based on supplying just-enough nutrition to optimize cost and production. Here are some guidelines on fruit nutrition from Steve Hoying, Horticulturalist at Cornell’s Hudson Valley Lab.
Determining nitrogen needs of apples is best done using leaf analysis combined with examination of last year's shoot growth and crop. Cornell apple leaf N recommendations are: (1) 2.4-2.6% for young non-bearing apples, (2) 2.2-2.4% for young bearing apples, (3) 1.8-2.2% for mature soft variety types (like Cortland, Honeycrisp, Jonamac and McIntosh), (4) 2.2-2.4% for hard varieties (like Red Delicious, Empire, Gala, Rome).
In the absence of last year’s leaf analyses, infer N need based on last year's shoot growth and fruit condition, and on older nutritional analyses: (1) Bearing trees with low N status may have terminal shoot growth less than 8 inches long, and may have produced highly-colored, early-maturing fruit. However, trees that did not receive adequate supplemental irrigation may also show limited shoot growth, (2) Bearing trees with excessive N status have shoot growth over 18" and poorly-colored fruit, (3) Also, consider leaf and soil analyses from 2 or more years ago. Combined with growth observations, older nutritional data will give useful, if not ideal, indications of N needs. Plan to do leaf analyses this year if you find yourself relying on older data, (4) The optimal timing for N application may be green tip through bloom, or a split application at green tip followed by a second between bloom and petal fall. Avoid application of N after shoot growth begins because it may contribute to higher fruit N levels. Another strategy would be to apply N shortly before harvest or right after harvest to provide higher reserve N levels for the next year.
A "standard" fertilizer program for bearing apples where leaf analysis shows no major deficiencies and no deficiency symptoms are visible could include: (1) a soil application of 20-40 lbs of actual N; 50-80 lbs KCL; 2 lbs B, (2) at green tip - 4 lbs C-O-C-S or Kocide per 100 gal, (3) at tight cluster to pink - one spray of 3 lbs. feed grade low biuret Urea plus 1 lb. Solubor per 100 gal, (4) At first cover - foliar spray of Zn-EDTA at label rate, (5) at petal fall, first and second cover - 3 sprays Epsom salts per 100 gal., especially on McIntosh to reduce drop, (6) beginning at 1st or 2nd cover, 3 foliar sprays of 1-2 lbs calcium chloride per 100 gal, (7) during the period of shoot growth - 3 more calcium chloride sprays at 3-4 lbs per 100 gal.; Bitterpit-susceptible varieties should receive 6 or more calcium sprays per season, and (8) after harvest - supplemental potassium as needed; 2-3 tons dolomitic lime every 2-3 years.
Recommended Leaf N Levels for Stone Fruit: (1) 2.4-3.4% for apricots, cherries and plums, (2) Above 3.0% and closer to 4.0% for peaches, (3) The best peaches are produced on pencil-sized one-year old wood. The presence/absence of adequate amounts of such wood is another way to determine how your N fertilizer program should be adjusted.
Stone fruit nutrient needs are similar to apple but have important differences: (1) The common apple orchard broadcast fertilizer mix (1-0-2 of N-P-K plus B) is not recommended for stone fruit. Do not apply higher rates of custom-mixed apple fertilizer blend to stone fruit in order to meet their higher N needs, (2) Unlike apples, stone fruit do not require a large amount of potassium. Careful analysis of leaf samples is important to judge the amount of potassium needed. In addition, stone fruit are very sensitive to chlorides; the sulfate form should be substituted for the muriate form when large applications of K2O are called for in the leaf analysis, (3) Both excess and deficiency of Boron can reduce fruit quality in stone fruit. Rates of boron for soil application in stone fruit orchards should not exceed 1 lb per acre (equals 1/2 of the rate suggested for apples and pears) unless both soil and leaf analysis results indicated that greater amounts are required.
For more in-depth information on orchard nutrition programs, review the 2013 Cornell Crop and Pest Management Guidelines (Chapter 10: Nutrient Management of Apple Orchards) and your old copy of Orchard Nutrition Management; Bulletin 219 CCE published by Stiles and Reid.
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