Page 96 - Plant-Based Remediation Processes

5 Impact of Metal/Metalloid-Contaminated Areas on Plant Growth 85

manganese on plants. On the other hand, the excess of this cation in soil limits the
availability of potassium, magnesium, iron, and, in particular, of zinc, manganese,
and phosphorus. High soil copper content reduces possibilities of uptake by plants
of iron, zinc, and manganese. In turn, zinc, manganese, and boron enhance the
absorption of potassium and limit magnesium availability. In heavily limed soils,
we observe low concentrations of boron in plant biomass, whereas shortages of
molybdenum usually occur in plants cultivated on acid soils rich in iron (Czuba
1996). In the course of plant growth, it is possible to evaluate possibilities of their
supply with nutrients contained in the soil in relation to the real state of nourish-
ment by (Czuba 1996):

• Determination of plant available forms of macro- and microelements in the soil
• Determination of constituents in plants
• Observation of plants during different stages of their growth and development
(identification of visible deficiencies)
Foliar application of fertilisers is one possible method of supplementation of the
basic soil fertilisation. In such case, urea is used as a source of nitrogen, magnesium
sulphate heptahydrate as a source of magnesium, and multi-component liquid
fertilisers are applied as a source of many microelements.

5.3 Changes of Soil Parameters as Factors of Growth
Stimulation or Inhibition

Apart from soil nutrient availability (macro- and microelements), there are a
number of other soil parameters affecting plant growth and development or inhibi-
tion. They include properties that were inherited by soils from their parent material
and which are relatively stable as well as anthropogenic properties resulting from
geomechanical, hydrological, and chemical transformations. The most important
soil parameters determining plant growth and development are physical
parameters: soil texture, bulk density, porosity, as well as structure and water
capacity. With respect to chemical parameters, the most important are content of
organic matter, sorption, reaction, and buffer capacities. The most important,
unchangeable soil character inherited from the parent material is soil texture. It
refers to the size of individual soil grains (fractions) and their percentage composi-
tion in the soil solid phase. The most important role is played by clay fractions made
up of clay minerals (silicates and aluminosilicates) which exert a decisive influence
on nearly all soil characteristics. On the basis of texture, the following soils can be
distinguished: sandy, loamy, clayey, and silty (Fig. 5.2). From among the above-
mentioned mineral soils, the most advantageous for the majority of crop plants are
silty formations followed by loamy and clayey soils; sandy soils are the worst in this
regard (Mocek and Drzymała 2010). Soil bulk density expresses the ratio of the
solid phase to total soil volume. In the case of top layers of mineral soils, this
1
parameter can fluctuate in the range of 0.9 to 1.9 g mL , although most frequently