136
Subtle Agroecologies
capacitance can, in some circumstances, be correlated with root mass, it is not a direct assay of root
mass (Figure 12.2).
In 2015, Koppert Biological Systems performed a dedicated propagation trial with cucumbers
grown in perlite to validate the fndings of Dietrich (2013) and Cseresnyés et al. (2013) in a greenhouse situation (Moerman and Weber, unpublished research, 2015). Measurements of the phase
angle and dry root weight of 2 groups of 25 plants taken on 4 and 9 March 2015 confrmed the
FIGURE 12.2 Resistance–capacitance (RC) circuits according to the revised model: (a,c) diagrams of barley
plants with fve root tips, (b,d) electrical equivalent networks of the root systems showing the location of the
RC components, (a,b) RC circuits for a completely submerged root system and (c,d) RC circuits for a partly
submerged root system. The sub-circuit that largely determines the capacitance is ringed to emphasise its
importance. Note that the individual RC components can have different values.