Nieuwkoop DM-5 Mode D'emploi page 5

Purpose of the pH-meter
To make the soil suitable for the absorption of fertiliser, acidic soil must be neutralised with lime or a lime-
based fertiliser. However, if too much lime or lime fertiliser is used, the result will be a manganese deficiency
causing 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 basis on which to decide how much lime
must be added. This can be simply done with the pH-meter which has already been successfully used by many
market gardened. A perfectly neutral soil has a pH = 7; the instrument should always indicate this value before
taking any readings.
How to use the pH-meter
1. Take the instrument out of its case and check that the needle indicates pH 7 (fig.1). If this is not the case it
can be very simple adjusted. Remove the cover and glass window from the instrument and carefully turn the
adjusting screw clockwise or counter-clockwise, as the case may be.
2. The electrode is very vulnerable and should carefully cleaned with water and dried with a clean cloth before
and after use (fig.2). This is very important since otherwise the reading is not correct. After cleaning, the
electrodes should not get in contact with anything, not even with your hands since these always give off some
transpiration, however slight, and this would adversely affect the readings.
3. Fill the soil holder with the soil under test and pack the soil so as to be sure that the complete electrode
surface will be in contact with it. Insert the instrument into the soil until the silver-coloured electrodes are
completely covered with soil. Then turn the instrument two or three times about its longitudinal axis to ensure
good contact between soil and electrodes (fig.3).
Black earth, clay. loam etc. should have a moisture content (shown on the meter) between 50 and 70%.
If the soil is too wet, the water should be pressed out until the moisture content is at a minimum 50%. Humus-
rich soil may have higher moisture content, even exceeding 100% as is often the case. If the soil is too dry, the
pH cannot be measured; in that case it should first be moistened with distilled water; readings can then be taken
after about 2 hours.
4. 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 thoroughly with water and wipe off with a dry cloth (fig.2).
Normal soil used for cultivation will seldom have a moisture content below 30% as is the case e.g. with dry
sand.
5. It takes the needle about three minutes to get stabilised. Next the pH can be read off (fig.4). DO NOT allow
the meter to stay in the soil for more than 5 minutes. This will prevent undue corrosion of the electrodes.
Plus points of the pH-meter
1. Since the instrument generates its own current when in contact with the soil, no chemicals, distilled water
and/or external source of current, such as a battery, are required.
2. Measuring is extremely simple: just insert the electrode into the soil and the pH can be read off a few
minutes later (clean instrument with water before and after use).
3. The instrument is compact, of attractive design and easy to carry along.
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