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Leaf Analysis Time is Approaching

Posted: June 27, 2011

This past winter at some of the fruit schools, I talked about the need to determine the nutrient status of your orchards through leaf analysis. Unlike vegetable crops, tree fruit and small fruit are not replanted every year and their roots are capable of absorbing nutrients any time the conditions are favorable. There is also a considerable amount of nutrient recycling. Nutrients in leaves that fall to the ground or brush that is cut from the trees and chopped in the orchard are recycled and made available again to the trees. Only a small portion of the nutrients are removed in the form of the fruit. Leaf analysis also can determine micronutrient levels in the tree. Soil tests for micronutrients are very difficult to validate.
Dr. Rob Crassweller, Penn State Pomologist

For leaf analysis to be of value for predicting the nutritional status of your orchard you must follow certain procedures. First, nutrient levels in fruit trees are most stable from mid-July to mid-August. Samples of leaves are therefore collected during this period. Earlier in the season, some nutrient levels are very erratic and do not provide a true gauge of their levels. Samples taken after mid August can be influenced by the natural development of hardening off for winter.

Fully expanded leaves should be collected midway on the current season’s growth. Collect only healthy looking leaves that are free of disease and insect damage. The best sample is one collected from a single variety on a single rootstock. The next best sample is of a single variety. Never combine multiple varieties in a sample. Some varieties have different nutrient requirements especially nitrogen. Select leaves from shoots that are about chest high, and randomly walk in a zigzag pattern through the block collecting no more than 2 leaves from any one tree. Leaf samples should consist of 50 to 60 leaves. Place the leaves in a brown paper bag and set somewhere inside to dry out. Never place leaves in a plastic bag where they might mold.

There are a number of commercial laboratories that provide leaf analysis services. Many of the laboratories formerly run by the universities have been closed. Fortunately, we still have the Ag Analytical Services Lab in operation at Penn State. Beginning last year the lab has the capability of sending results via a pdf document over email. If you would like this service, be sure to include your email address near your mailing information. For those that send in samples to Penn State, I look at all the results and then send them back to the lab with specific recommendations when needed. You may obtain sample kits from your local county extension office or print the plant tissue submission form found at http://www.aasl.psu.edu/plant_tissue_prog.html. Current price for the Penn State testing kit is $24.00. The standard analysis includes the macronutrients N, P, K, Ca, Mg, plus the micronutrients Mn, Fe, Cu, B, Al, Zn, Na and S.

One thing I would like to stress is the importance of providing as much information on the data sheet as possible. Many times we can detect problems that are not related to nutrient deficiencies. The information is also utilized to give a more thorough recommendation.