User manual

7
2 pH-Meter Soiltester (english)
2.1 Purpose of the Soiltester
To make the soil suitable for the absorption
of fertilizer, acidic soil must be neutralized
with lime or a lime-based fertilizer. However,
if too much lime or lime fertilizer is used, the
result will be a manganese deficiency caus-
ing complete infertility of the soil. Therefore,
if a lime treatment of the soil is required, it is
recommended first to determine the degree
of acidity, i.e. the pH of the soil to have a ba-
sis on which to decide how much lime must
be added. This can be simply done with the
pH-Meter Soiltester which has already been
successfully used by many market garden-
ers.
2.2 How to use the Soiltester
a) The electrode is very vulnerable and should
carefully be cleaned with water and dried
with a clean cloth before and after use. This
is very important since otherwise the read-
ings are not correct. After cleaning, the elec-
trodes should not get in contact with any-
thing, not even with your hands since these
always give off some transpiration, however
slight, and this would adversely influence the
vallue.
b) Fill the soil holder with the soil under test and
pack the soil as to be sure that the complete
electrode are completely covered with soil.
Then turn the instrument two times about its
longitudinal axis to ensure good contact be-
tween soil and electrodes.
Black earth, clay, loam etc. should have a
moisture content (shown on the meter) be-
tween 50 % and 70 %. If the soil is too dry,
the pH can not be measured; in that case it
should first be moistened with distilled wa-
ter; readings can then be taken after about
two hours.
c) To measure the moisture content in the soil,
press the white button; the moisture content
can be read off immediately. After use, clean
the electrodes carefully with water and wipe
off with a cloth. Normal soil used for cultiva-
tion will rarely have a moisture content be-
low 30 % as it is the dase e.g. with dry sand.
d) It takes the needle about three minutes to
get stabilized. The the pH can be read off.
DO NOT allow the meter to stay in the soil for
more than five minutes. This will prevent un-
due corresion of the electrodes.
e) A perfectly neutral soil has a pH = 7; the in-
strument should always indicate this value
before taking any readings.
2.3 Advantages of the Soiltester
a) Since the instrument generates its own cur-
rent when in contact with the soil, no chemi-
cals, distilled water and/or externat source
of current, such as battery, are required.
b) Measuring is extremely simple: just insert the
electrode into the soil and the ph can be read
off after a few moments.
c) The instrument is compact, of attractive de-
sign and easy to carry along.
2.4 Practical hints:
a) A fluctuating needle may have any of the fol-
lowing causes:
– The soil does not completely cover the
electrodes.
– High salt content in the soil.
– High iron, magnesium content etc.
– The soil has recently been manured so
that you actually measure the manure.
b) Keep the electrodes clean and free from rust.
Rusty electrodes can carefully be cleaned
with sandpaper (article 3023). Surface cor-
rosion will detrimentally affect the sensitivity
of the instrument which in that case will no
longer indicate reliable pH and moisture val-
ues. After cleaning, wait at least half an hour
before taking readings.
c) H.T. masts or other sources of stray currents
in the neighbourhood of the soil to be mea-
sured are likely to cause the instrument to
give too high pH and moisture values. In such
places accurate readings are impossible.
d) Since the operation of the instrument is
based on current generation through contact
with the soil, the readings depend to some