Plant Analysis: A Diagnostic Tool for Monitoring Nutrient Status of Perennial Fruit Crops

Published: July 1, 2011

Plant analysis has proven to be a very effective means of predicting fertilizer needs for perennial fruit crops, and 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, etc.), plant analysis is the best way to monitor the plant's nutrient needs. Plant analysis can be used to fine tune the efficiency of a fertilizer program before nutrient deficiency symptoms occur and is very useful in improving the fruit quality and yield. Fertilization practices can be monitored by sampling leaves or petioles mid-season, and making adjustments for the following year.

Foliar samples for perennial fruit crops are typically taken once the plants start bearing regular fruit. Plant tissue samples are 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 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. For plant nutrient analysis for orchards, the leaf sample should be collected between July 15th and August 15th. Table 1 lists the proper time and plant parts to sample for perennial fruit crops.

Submitting Plant Samples for Analysis
When submitting plant samples, 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. Wash dusty plants before air-drying. Fresh plant samples should not be placed in closed plastic bags unless the tissue is air-dried or the 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 regular plus micronutrients analysis package which includes nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron(Fe), zinc(Zn), manganese (Mn) or the complete nutrient analysis package which includes all the above tests plus boron (B), molybdenum (MO) and sulfur (S). The University of Missouri soil and plant testing lab offers regular plus micro nutrient analysis for $23 per sample and the complete nutrient analysis package for $30 per sample. All the samples submitted should be accompanied by duly filled sample information form and check written out to "MU Soil Testing" for the amount due. Counties and firms that have accounts with the lab can provide county code and firm number in the sample submission form so that they can be billed. Sample information forms can be downloaded from: http://soilplantlab.missouri.edu/soil/forms/index.aspx. Additional 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/