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Plant Nutrient Testing Article

Plant Nutrient Testing and Sufficiency Ranges for Florida Watermelons

Mark Warren, UF/IFAS Levy County Extension Agent, Bronson, FL

Many producers and consultants use whole leaf tissue sampling as an important management tool for in-season fertility assessments. Like petiole-sap testing, it is important to recognize that tissue tests are just snap-shot views of the crop at the time the sample was collected. Consider that results can be affected by many factors (time of day, cloud cover, stage of maturity, time since last fertilizer application). Leaf tissue analysis and petiole-sap tests are most valuable when taken consistently, routinely, and then the results considered over time.

Proper sample collection is the most critical part of the process. Representative samples are essential. Avoid taking samples from areas that have symptoms not related to nutrition (disease, cold, insect, drought…) Some tissue testing labs may suggest different sampling protocols (whole plant, petiole, full leaf), but UF research, including the nutrient sufficiency/ deficiency ranges, are based on samples of the “most recently matured leaf” (MRML). Regardless of the lab that you choose, you should submit samples using the MRML (5-6th leaf from tip, see photo) as these will most accurately correlate to the published information for Florida crops and conditions.

· 15-20 leaves

· Full leaf samples collected/ submitted in paper bag

· Petioles for sap testing should be collected, immediately trimmed (petioles only), put in plastic bags, and stored on ice or refrigerator until testing.

Photo: Bob Hochmuth

When nutrient related stress is suspected, it is best to submit a “good” versus “bad” set of samples so that the results can be compared.

Results from different labs can vary in how they are interpreted and presented. Units of measure may differ, graphic elements may be included, and even corrective recommendations may be offered, but all accredited labs using common methods should provide reasonably similar numeric results.

It is important to recognize is that the interpretation of the results (the pretty part of the report) may or may not take your local crops, soils, and conditions into account. While easy to look at, bar graphs may be misleading. Use the values from the table below developed by the University of Florida IFAS to interpret your results and you will have a more regionally accurate indication of your crop’s status.

Adapted from, Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida. HS964.

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