User Guide

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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.