Take the following steps into account when collecting leaf samples: Avoid the outer rows of the greenhouse. Also avoid the first and last 10 meters of a row. Sample leaves with an average leaf quality. Sample abnormal plants with e.g. deficiency symptoms separately. Might a deficiency be present in the young or old leaves of the total crop, then sample these leaves regularly as a young or old leaf sample.
Take into account the sunny and shady side of the plant. Always consistently sample the same side.
Time of sampling
It is strongly recommended to take the samples before 9:00 AM. The plant will then have enough leaf-tension with proper moisture conditions.
For a young leaf sample, pick the youngest, fully developed leaves, about 50 - 100 cm. from the top of the plant (depending on the growing stage of the plant). Also pick (separately) the oldest, but still vital leaves. This is the l11 or 2nd vital leaf from the lowest part of the plant (see pictures 1-4). Stack the leaves for each sample and remove the petioles, as they will not give a good indication and influence the sample.
For an average, representative sample about 10 leaves are needed. Of course sample size can vary, depending on leaf type (size and thickness). Might you doubt about the sample size, please feel free to contact us.
Packing the leaf samples
Please pack the young and old leaf samples separately, these will be two different samples. To assure fluent processing please stack the leaves, fold the leaves if needed, and put them in a plastic zip-lock bag carefully. Make sure all air is out, so any leaf evaporation is excluded. See pictures below (tomato leaf as an example).