LaMotte STH Series - Manual (Page 25)

Green Plant Tissue Tests
Testing an extract prepared from fresh plant tissue provides a
means of verifying suspected nutrient deficiencies during plant
growth. Plant tissue testing is discussed in the LaMotte Soil
Handbook. The necessary information for testing nitrate nitrogen,
phosphorus, and potassium in green plant tissues is given below.
These tests are meant to be used in a comparative manner. It is
important to test tissue from healthy plants as well as those from
problem plants. Interpretations should be based on comparison of
test results from plants of the same species and same age, grown in
the same general environment. Since test reactions may vary from
species to species, at different stages of growth, or under different
growing conditions, it is not possible to accurately quantify test
results. The color charts should be used in a comparative manner.
Relative values from very deficient to abundant have been
assigned to the range of possible test reactions under each factor
below.
Preparation of Tissue Extract
1. Select a small lot of the leaf petioles or succulent portion of
the stem. When testing problem plants, collect tissue from
those areas where the abnormality is most observable.
2. Use a clean, sharp knife or a razor blade to cut the material
into fine bits not more than 1/8" to 1/16" in length and
thickness.
3. Fill an Extraction Tube (0704) to the lower mark with this
material. Do not pack down.
4. Add *Universal Extracting Solution (5173PS) to the upper
mark. Cap and shake vigorously for five minutes.
5. Use a piece of filter paper (0465) and a plastic funnel (0459),
filter the mixture into a second Extraction Tube (0704). This
filtrate is the tissue extract to be used in place of the general
soil extract in the nitrate nitrogen, phosphorus, and
potassium test procedures.
23