Leaf analysis (also called tissue analysis or foliar anaylsis) is an excellent means of monitoring plant nutrient levels. With perennial fruit crops, leaf analysis is even better than soil tests for determining an optimal fertilization program. While soil tests reveal the quantity of certain nutrients in the soil, leaf analysis shows exactly what the plant has succeeded in taking up. However, soil tests are necessary for determining soil pH and thus lime (or sulfur) recommendations. If nutritional problems are suspected in a given planting, it's a good idea to take both leaf and soil tests.
Leaf analysis is helpful for detecting nutrient deficiencies (especially of minor nutrients) before they effect plant health or yield. The best tissue analysis for berry crops comes from green, healthy, whole leaves. Do not submit plant tissue that has disease, leaf burn, insect or hail damage. Keep the material in a cool place (insulated chest) or refrigerate before mailing. Record all foliar sprays in case the results are influenced by nutrient or pesticide applications.
A minimum of 50 leaves from raspberries or strawberries, and 80 to 100 leaves from blueberries should be selected for each analysis. Do not mix leaves from fields with different soil types or management histories. Do not combine leaves from healthy plants with plants that are not growing well. Strawberry samples should be taken from the first fully-expanded leaves after renovation, about July 15 to August 15. Raspberry samples should be leaves from non-fruiting canes taken between August 1 and 20. Blueberry samples should be leaves taken during the first week of harvest, from July 15 to August 15.
Place samples in sealed paper bags, clearly labeled with field names. For information on Land Grant University labs in the Northeast that perform plant tissue analyses, see the University of Vermont Ag Testing Lab's web site http://pss.uvm.edu/ag_testing/
Here are the tables from the New England Small Fruit Management Guide
showing desired ranges of nutrient concentrations in small fruits. Vermont
growers can ask the lab to send me a copy of their test results, and then
contact me for specific fertilizer recommendations: firstname.lastname@example.org