Hanna Instruments HI 99121 User Manual
Instruction Manual
HI 99121
Soil pH
Test Kit
SPECIFICATIONSSPECIFICATIONS
SPECIFICATIONS
SPECIFICATIONSSPECIFICATIONS
ISO 9000 Certified
Company since 1992
http://www.hannainst.com
Dear Customer,
Thank you for choosing a Hanna Product. Please read the instruction manual
carefully prior to use. It will provide you with necessary information for the
correct use of the kit.
Remove the test kit from the packing material and examine it carefully to make
sure that no damage has occurred during shipping. If there is any noticeable
damage, notify your Dealer or the nearest Hanna office immediately.
Each kit is supplied with:
• HI 991000 portable pH meter
• HI 1292D pH electrode
• HI 721319 soil drill
• HI 7051M soil preparation solution
• HI 70004 buffer solution pH 4.01 (1 pc.)
• HI 70007 buffer solution pH 7.01 (1 pc.)
• HI 721312 hard carrying case
• HI 740036 100 ml plastic beaker (1 pc.)
Note: Any damaged or defective item must be returned in its original packing
materials.
Note: Read the HI 991000 instruction manual to ensure correct use of the
meter.
SOIL SOIL
SOIL
SOIL SOIL
pH is the measure of the hydrogen ion concentration [H+]. Soil can be acid,
neutral or alkaline, according to its pH value.
Fig. 1 shows the relationship between the scale of pH and types of soil. Most
plants prefer a pH range from 5.5 to 7.5; but some species prefer more acid or
alkaline soils. Nevertheless, every plant requires a particular range of pH, for
optimum growth.
Fig. 1. T ypes of soil according to the pH value
pH strongly influences the availability of nutrients and the presence of microorganisms and plants in the soil.
For example, fungi prefer acidic conditions whereas most bacteria, especially
those supplying nutrients to the plants, have a preference for moderately acidic
or slightly alkaline soils. In fact, in strongly acidic conditions, nitrogen fixing and
the mineralization of vegetable residual is reduced.
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HH
p
H
pp
HH
2
Plants absorb the nutrients dissolved in the soil water and the nutrient solubility
depends largely on the pH value. Hence, the availability of elements is different
at different pH levels (Fig. 2).
Each plant needs elements in different quantities and this is the reason why
each plant requires a particular range of pH to optimize its growth.
For example, iron, copper and manganese are not soluble in an alkaline
environment. This means that plants needing these elements should theoretically
be in an acidic type of soil. Nitrogen, phosphorus, potassium and sulfur, on the
other hand, are readily available in a pH range close to neutrality.
Fig. 2. Solubility of the elements according to varying pH values
Furthermore, abnormal pH values, increase the concentration of toxic elements
for plants. For example, in acid conditions, there can be an excess of aluminum
ions in such quantities that the plant can not tolerate.
Negative effects on chemical and physical structure are also present when pH
values are too far from neutral conditions (break up of aggregates, a less
permeable and more compact soil).
Management of the soil in relation to the pH value
Once the pH value is known, it is advisable to choose crops that are suitable for
this range (e.g. in an acid soil, cultivate rice, potato, strawberry).
Add fertilizers that do not increase acidity (for example urea, calcium nitrate,
ammonium nitrate and superphosphate) or lower alkalinity (e.g. ammonium
sulfate).
It is recommended that a cost evaluation is made prior to commencement of the
soil pH modification. Corrective substances can be added to modify the soil pH,
however, the effects are generally slow and not persistent. For example, by
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