Plant Nutrition

Nutritional requirements of fruit trees differ from those of agronomic crops, cover crops, and orchard sod. Growers may estimate fruit trees’ nutritional needs through leaf and soil analysis, tree growth and cropping, and past experience. Since fruit trees are a perennial crop, leaf or foliar analysis is the most accurate way to determine nutritional status of an orchard. Factors such as rootstock, crop load, soil type, and weather conditions influence whether or not trees are absorbing enough nutrients to produce maximum yields of high-quality fruit.

Foliar analysis can also be of value in diagnosing the cause(s) of abnormalities in plant growth or fruit development. While only a single sample may be needed, paired samples, one from normal foliage and one from abnormal foliage, are frequently helpful. Foliar analysis, particularly if done over a period of years, can warn of an approaching deficiency or toxicity before the plant shows any visible symptoms.

Soil analyses, on the other hand, are not nearly as accurate in determining the nutritional status of an orchard. They do, however, play an important role in fertility programs when used in specific situations. In established orchards the main value of a soil test is to monitor soil pH. A soil test should also always be taken before an orchard is planted, since it is much easier to adjust nutrient levels before the trees are established. Renovating older orchards disturbs the subsoil enough to alter the soil test results. Therefore, when removing an old orchard for replanting, it is best to collect a soil sample after all the roots have been removed and any grading or soil disturbance has been completed.

Occasionally, soil and leaf analyses may offer opposing recommendations for fertilizing with phosphorus, potassium, and magnesium. If this occurs, follow the recommendations listed on the leaf analysis. However, if the soil analysis recommends lime, lime should always be applied.



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