LaMotte STH Outfit - Manual (Page 20)

20
Green Plant Tissue Tests
Testing an extract prepared from fresh plant tissue provides a means of
verifying suspected nutrient defi ciencies 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 defi cient 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 fi ne
bits not more than 1 /
8
” to 1 /
16
” in length and thickness.
3. Fill an Extraction Tube (0704) to the lower line with this material.
Do not pack down.
4. Add *Universal Extracting Solution (5173PS) to the upper line. Cap
and shake vigorously for fi ve minutes.
5. Use a piece of fi lter paper (0465) and a plastic funnel (0459), fi lter
the mixture into a second Extraction Tube (0704). This fi ltrate is the
tissue extract to be used in place of the general soil extract in the
nitrate nitrogen, phosphorus, and potassium test procedures.