LaMotte STH Series - Manual (Page 20)

Nitrite Nitrogen
Nitrites are formed as an intermediate step in the production of
nitrates. Soils that are well drained and aerated contain only small
amounts of nitrite nitrogen. Excessive nitrites, which are toxic to
plants, may result from soil conditions unfavorable to the
formation of nitrate, such as inadequate aeration. High nitrite
readings may also be encountered in soils with large amounts of
nitrates, where a portion of the nitrate nitrogen decomposes to
form nitrites.
Procedure:
1. Use a transfer pipet (0364) to add 5 drops of soil extract to a
large depression on a spot plate (0159).
2. Add 1 drop of *Nitrite Nitrogen Reagent 1 (5151PS).
3. Add 1 drop of *Nitrite Nitrogen Reagent 2 (5152PS). Mix
with a clean stirring rod.
4. Add 3 drops of *Nitrite Nitrogen Reagent 3 (5153PS). Mix
with a stirring rod. Wait 1 minute.
5. Match sample color to a color standard on the Nitrite
Nitrogen Color Chart (1310). Record as ppm nitrite nitrogen.
6. If sample color matches, or is deeper than, the highest
standard, repeat test on a diluted sample. Transfer one drop of
soil extract to a large depression on a spot plate. Add 4 drops
of *Universal Extracting Solution (5173). Follow Steps 2-5.
Multiply final result by 5. Record as ppm Nitrite Nitrogen.
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