Table 1 Soil and sample properties and scanning parameters for X-ray computed tomography

Cultivation parameters

Experimental conditions

Pot experiment (controlled conditions)

Samples collected in situ in the field

Samples collected in situ in the field

Samples collected in situ in the field

Soil type

Klein-Altendorf: Haplic Luvisol, sieved

Eschikon: Eutric Cambisol; Reckenholz: Pseudogleyed Cambisol

Eschikon: Eutric Cambisol

Reckenholz: Pseudogleyed Cambisol

Plant age (months)

0.5

8

8

24

Cylinder internal diameter (cm)

6

3.4

10

3.4 (small samples) and 10 (large samples)

Cylinder material

PE

PVC

PVC

PVC

Number of plants per cylinder

4

1

1

>1

Acquisition parameters

Height of scanned part of root system (cm)

16

15

10

15 (small samples) and 10 (large samples)

Height of analyzed part of root system (cm)

4

15

10

15 (small samples) and 10 (large samples)

Voxel size (mm)

0.05

0.044

0.120

0.120 (large samples) and 0.044 (small samples)

Binning

1 × 1

2 × 2

2 × 2

2 × 2

Current (µA)

450

350

450

450 (large samples) and 350 (small samples)

Voltage (kV)

180

120

120

120

Number of images per subscan

3000

1600

1600

1600

Averaged images

3

1

1

1

Skipped images

1

0

0

0

Filtering

0.1 mm copper

0.1 mm copper

0.4 mm copper

0.4 (large samples) and 0.1 mm (small samples) copper

Observation ROI option

yes

yes

yes

yes

Exposure time per image (ms)

200

131

1000

131 (small samples) and 1000 (large samples)

Scan duration (min)

120

41

30

30

Multiscan and number of subscans

Yes (3)

Yes (3)

No

Small samples: yes (3), large samples: no

Reconstruction parameters

Downscaling to unsigned 16 bit

Yes

Yes

Yes

Yes

Reference ROI

Yes

Yes

Yes

Yes

Auto scan optimizer

Yes

Yes

Yes

Yes

Beam hardening correction

Assuming different materials, value 4

Assuming different materials, value 3.6

Assuming different materials, value 3.6

Assuming different materials, value 3.6