When growers send in strawberry leaves for a nutrient analysis, should the petioles remain attached or be removed?
Whether you are in matted-row or plasticulture production, please be sure to remove the petioles from strawberry leaf samples that you send in to labs.
The standards were developed from leaf blades without the petioles. The next question is, “But does it matter?”
Here is a shortened repeat of an article from 2003 when we had analyzed many samples (nearly 200) to answer questions regarding strawberry tissue analyses.
Instructions included with plant analysis kits do state to remove the petioles, but a discussion with lab personnel at the Penn State Plant Analysis Lab revealed that nearly all strawberry samples received from growers have consisted of the leaf petiole plus blade.
We collected samples of separate petioles and blades to determine whether this discrepancy makes a significant difference in sample results (i.e., could cause incorrect diagnoses). There was a significant difference in the nutrient concentrations in petioles and leaves, plus the petiole is a fairly large proportion of the dry weight, so incorrect interpretations could easily result due to a failure to remove the petioles from samples sent in for a nutrient test.
The nitrogen concentration in the petioles was half that in the leaf blades, while the potassium concentration was double. Other elemental concentrations which varied widely between petioles and leaf blades were manganese and the micronutrients manganese, iron, copper, boron, and zinc. The percentage of dry weight of the sample that the petiole comprised ranged from 12% with ‘Earliglow’ in samples early in the season, to 30% with ‘Sweet Charlie’ in samples taken later. Therefore, if the petiole is included as part of the sample, it would be easy for deficiencies to be diagnosed that don’t exist, or to be missed when in fact present.
(Source – http://www.farms.com/news/sampling-strawberry-leaves-for-nutrient-analysis-93570.aspx)