Plant analysis has proved to be a very effective means of predicting fertilizer needs for perennial fruit crops. It has been used as a diagnostic tool for many years. To determine nutrient deficiencies, most growers rely primarily on visual symptoms, plant tissue analysis and soil analysis. Plant analysis and soil testing go hand in hand. A soil test provides an index of the nutrient that is potentially available for the crop. Plant analysis tells how much of that potentially available nutrient is actually taken up by the plant.
For perennial fruit crops (blueberries, strawberries, apples, grapes, peach, nectarine, etc.), plant analysis is the best way by which to monitor the plant's nutrient needs. Fertilization practices can be monitored by sampling leaves (apples, peaches and nectarines) or petioles (grapes and blueberries) during mid season and making adjustments for the following year.
Foliar samples for perennial fruit crops are typically taken once the plants start bearing regular crops. Plant tissue sample is taken from plants when the nutrient levels in the leaves are relatively stable. The analysis and interpretations are of little value without the use of standard and consistent sampling procedures. In general, plant samples for perennial fruit crops are taken at midseason. Usually the leaf plus petioles or just the petiole alone is sampled for plant nutrient analysis. If the level of the nutrients falls outside the optimum range, the corrective measures should be taken. Optimum nutrient ranges are based on samples collected at a particular growth stage. Since the results of the plant analysis will be compared to known standards, it is important that parts of plants are sampled at a certain stage of development.
The leaf nutrient concentrations vary throughout the growing season. The general nutrient status of grape vines and orchards should be evaluated annually. This will help in evaluating the response for applied fertilizer. July to August is the best time to monitor the nutritional status of grapes, apples, pears and nectarines to make adjustments in the fertilizer program to avoid nutrient deficiency and to improving the fruit quality and yield for the following season. For plant nutrient analysis for orchards, the leaf sample should be collected preferably between July 15th and August 15th. Table 1 lists the proper time and plant parts to sample for perennial fruit crops.
Table 1: How and When to Sample Perennial Fruit Crops?
|Crop||Stage of Growth||Plant Part /Location on Plant||Number of samples|
|Apples||July 15 – Aug. 20||Fully-expanded leaf from middle of current terminal shoot.||30 leaves and petioles|
|Blueberries||First week of harvest||Young mature leaf from current season’s growth.||30 leaves detach petioles|
|Brambles||Aug 1 –Aug 21||Select the most recent fully expanded leaf blade of each primocane.||30 leaves detach petioles|
|Fruit Trees (Peach, nectarine, plums, etc.)||July 15- Sept 1||Select shots at eye level from around the outside of the tree. Select shoots that make a vertical angle of 45-60 degrees to the ground. Remove 1 or 2 leaves from the mid portion of current season’s growth.||30 leaves and petioles|
|Grapes||Veraison*||Petiole from most recently matured leaf on shoot (1 petiole per shoot). * Veraison stage refers is the time when grape berries begin to soften and change color from green to red, blue, or yellow.||30 petioles|
|Raspberries||First week in Aug.||Leaf 18 inches from tip.||30 leaves|
|Strawberries||Mid Aug.||Mature leaves from new growth at flowering.||20 leaves|
Do not include plants affected by insects, disease or pesticide damage. Where a deficiency is suspected, take samples from normal plants in an adjacent area as well as from the affected area. It is important to take a soil sample from each area. Comparing soil and plant analysis results can greatly assist in the interpretations. Collected plant tissue is very perishable and requires special handling to avoid decomposition. Therefore, fresh plant tissue should be placed in clean paper bags left open; partially air dried if possible or kept in a cool environment during shipment to the laboratory. Wash dusty plants before air-drying. Fresh plant samples should not be placed in closed plastic bags unless the tissue is either air-dried or bag and contents are kept cool. Air-drying of fresh plant tissue can be done by placing the plant tissue in an open, dry environment for 12 to 24 hours. Air dried samples can be placed in a clean brown bag or envelope and mailed to the lab. Request a complete analysis of each plant sample including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sulfur (S), zinc (Zn), and boron. The University of Missouri soil and plant testing lab offers this service for $30 per sample. You can also request for regular analysis (N, P, K, Ca, mg for $17 per sample) or regular plus micro nutrients analysis (N, P, K, Ca, Mg, Cu, Fe, Mn and Zn for $23 per sample). Information on submitting samples to the lab and sample information forms can be obtained from the lab’s website at: http://soilplantlab.missouri.edu/soil/
REVISED: July 2, 2012