How to Best Sample Strawberry Leaves for a Nutrient Analysis - That’s a Berry Good Question!!!
Posted: May 10, 2011
A. In 2003 to 2005, with the help of county extension educators and six growers, we tracked what was going on nutritionally in plasticulture plantings across the state. We collected and analyzed leaf samples (163 of them, thanks to funding from a PDA project) to figure this out.
The concentrations of nutrients in leaves vary widely over time depending on the season and what the plant is doing, no matter what production system you are using. Some nutrient elements can move in the plant after they are taken up (referred to as mobile nutrients) and others stay put in tissue in which they’ve been incorporated. Concentrations are different in leaves of different ages on the same plant, and also vary over time. With strawberries, two key elements that we are interested in are nitrogen and potassium. In similarly-aged leaves, concentrations of both elements increase very rapidly in the spring as the plant starts to grow, then stabilize briefly from early to mid-bloom, and drop again as the fruit forms. Based on the results of the project, in the plasticulture system we recommend taking samples of the most recently fully-matured leaves during early to mid-bloom, as we can interpret the results of leaf samples at that time (i.e., we can make a determination as to whether the nutrients are at optimum levels). If samples are taken at other times or different leaves are used, we can tell whether levels are rising or falling, but we really can’t correlate levels with yields – nutrient levels are simply changing too fast. Petioles (leaf stems) should be removed from the leaves, and just the trifoliate portion sent in as the concentration of nutrient in the petiole is different than the concentrations in the leaves. If you’ve sampled at other times of the season, you may be able to compare results of different plantings on your farm, but we can’t really say whether nutrient levels are normal or not. Also, be aware that results from some labs appear as “% of sufficiency range”. If you see a low number here, it doesn’t mean you are deficient until your nutrient levels are lower than the ones in the sufficient range. Seeing that you have a low “% of sufficiency” should be taken as a “heads-up”, but not necessarily a cause for panic. If you do detect deficiencies, nutrients applied through the irrigation system to correct the problem are detectable in the plant within 48 hours. It’s more difficult to tell what is going on with foliarly-applied nutrients as we can’t tell whether the nutrients are just on the leaf, or in the leaf. By the way, in matted-row production, taking leaf samples (of recently fully-expanded leaves) after renovation when leaves are regrown is still best.
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