Page 97 - Plant-Based Remediation Processes

86 M. Mleczek et al.

Fig. 5.2 Percentages of sand, silt, and clay in the major soil textural classes

it assumes the value of about 1.5 g mL 1 (Mocek and Drzymała 2010). Optimal
values of this soil feature for selected crop plants are collated in Table 5.2. It can be
concluded on the basis of the data presented in Table 5.2 that potatoes and sugar
beets (only at the beginning of vegetation) have relatively weak root systems
requiring extensive space for growth. Together with the increase of soil density,
1
compaction of the surface soil layer takes place, which, once it exceeds 1.8 g mL ,
makes growth and development of plant root systems impossible (Puchalski and
Prusinkiewicz 1990). Soil density changes during the vegetation period, and as a
rule, it increases with the passage of time, reaching a maximum at the beginning of
autumn. Increasing soil compaction can be attributed to many factors, the most
˛
important of which include (Rzasa and Owczarzak 2004):
• Natural (gravitational) settling of soil after ploughing
• Compaction of soil during field preparation for sowing as well as in the course of
performing agrotechnical operations
• Compacting action of soil water (mainly capillary)
• Ploughing at high soil water content
• Excessive proportion of root crop plants in the applied rotation system
accompanied by lack of structure-forming plants