Benchmarking electrical methods for rapid estimation of root biomass

Table 1 Signal frequencies leading to the highest scores for electrical variable depending on the chosen terminal configuration

Electrical variable	Terminal configuration	Sensitivity score	r ²_max	f _max (Hz)
C_p	2T	0.71	0.771***	78
	3T	0.72	0.787***	116
	4T	0.45	0.560	566
C_s	2T	0.48	0.520**	3
	3T	0.69	0.754***	6094
	4T	0.28	0.353	20,000
R_p	2T	0.44	0.657***	78
	3T	0.53	0.797***	841
	4T	0.00	0.377	9056
R_s	2T	0.45	0.642**	9056
	3T	0.54	0.791***	4101
	4T	0.00	0.348	20,000
G	2T	0.52	0.585**	78
	3T	0.68	0.751***	4101
	4T	0.31	0.398	20,000
Z	2T	0.43	0.645***	78
	3T	0.53	0.795***	1857
	4T	0.00	0.357	1,3458
X	2T	0.46	0.653**	20,000
	3T	0.55	0.794***	6094
	4T	0.00	0.330	20,000
θ	2T	0.05	0.331	20,000
	3T	0.10	0.752***	20,000
	4T	0.26	0.374	0.5

The sensitivity scores, the maximum of the coefficient of determination with root dry mass (r ²_max ) and the maximum determination frequency (f _max, in Hz), for parallel capacitance (C_p), serial capacitance (C_s), parallel resistance (R_p), serial resistance (R_s), conductance magnitude (G), impedance magnitude (Z), reactance (X) and phase angle (θ), in 2T, 3T and 4T configurations averaged for the three soil types studied
*** Linear regression is significant at the 0.01 level
** Linear regression is significant at the 0.05 level

ISSN: 1746-4811