Hanna Instruments HI 993310 - Manual (Page 3)

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particularly sensitive to soil activity. They require a lower quantity of
fertilizer because they utilize the reserve of nutrients in the seed. This
is true even for resistant species such as sugar beet and alfalfa.
Later on, plants can grow faster with proper fertilization, particularly
in conjunction with optimum lighting and temperature.
If slow releasing fertilizers are employed, their effectiveness can be
regularly controlled by testing the soil activity.
HIGH SOIL ACTIVITY
Soluble salts are indispensable for plant nutrition. However, when
dosed in excess, they can cause various anomalies as toxicity,
alteration of the nutrient absorption equilibrium, difficulty in absorb-
ing water, changing of the pH value and damaging of the soil
structure. For accurate pH measurements, use the Hanna HI 99121
pH meter, specially dedicated to soil application.
Some types of soils are naturally rich in salts. Apart from these, an
excessive use of fertilizers must be avoided and particular attention
must be paid to the use of water with high salt concentration.
If high values are detected, use the appropriate techniques to reduce
the presence of salts (washing away irrigation, reduction of fertilizer
dosages, addition of gypsum if the activity is caused by sodium, etc.).
IRRIGATION
Low measured values can be due to dry soil. In this case, add
demineralized water to the soil, and then repeat the tests. Even soils
rich in nutrients can give low values if they are not wet enough.
Irrigation schedules can then be made based on the measured value.
In case of waterlogged soil, very high values indicate stressed plants.
Find in the following pages a table with some indicative values for soil
activity required by some common plants.
SOIL ACTIVITY
Plants absorb nutritive elements dissolved in irrigation water. The ion
concentration of the soil solution depends on the type of soil. Soil can
be rich or poor in nutrients depending on its chemical composition
and its property in retaining water and chemical elements. For
example, clay soil retains more water than sandy soil since it holds
more cations and has a greater microporosity, so that there is a
different availability of ions for the roots.
If the soil is dry, fewer ions are at plant’s disposal. This is the reason
why conductivity readings have to be considered referring to water
presence and soil type.
The HI 76305 soil probe makes it easier to control the soil conditions
and to manage the crops.
SOIL PROBE
The HI 76305 soil probe provides a rapid response and an easy way
to test the soil activity in a variety of applications, as fertilization and
irrigation.
How to use the soil probe:
- Insert the probe in the soil where the roots are more dense or
numerous.
- The recommended depth is 10-15 cm (4-6") for lawn and young
plants, 20-30 cm (8-12") for vegetables and small plants.
- For plants with deep roots (e.g. trees, maize, sunflower, etc.), take
measurements at different depths, e.g. 30 and 50 cm (12 and 20").
- Take measurements in more spots to have a representative average.
- The soil has to be wet. If the soil is dry, add demineralized water.
- The probe tip must be in complete contact with the soil. If the
substrate is too soft, press it with your fingers to achieve a proper
contact.
- Wait until the value on the display is stabilized.
FERTILIZATION
By measuring the salt contents in soil and substrates, before and
after the fertilization, it is possible to have information about the soil
fertility and to design an appropriate fertilization plan. Consequently,
the plants will receive the right quantity of nutrients resulting in a
regular and rapid growth, greater resistance to disease and a more
appealing state manifesting their well being.
The younger plants, especially those that have just germinated, are
SOIL ACTIVITY