Low-field magnetic resonance imaging of roots in intact clayey and silty soils
The development of a robust method to non-invasively visualize root morphology in natural soils has been hampered by the opaque, physical, and structural properties of soils. In this work we describe a novel technology, low field magnetic resonance imaging (LF-MRI), for imaging energy sorghum (Sorghum bicolor (L.) Moench) root morphology and architecture in intact soils. The use of magnetic fields much weaker than those used with traditional MRI experiments reduces the distortion due to magnetic material naturally present in agricultural soils. A laboratory based LF-MRI operating at 47 mT magnetic field strength was evaluated using two sets of soil cores: 1) soil/root cores of Weswood silt loam (Udifluventic Haplustept) and a Belk clay (Entic Hapluderts) from a conventionally tilled field, and 2) soil/root cores from rhizotrons filled with either a Houston Black (Udic Haplusterts) clay or a sandy loam purchased from a turf company. The maximum soil water nuclear magnetic resonance (NMR) relaxation time T2 (4 ms) and the typical root water relaxation time T2 (100 ms) are far enough apart to provide a unique contrast mechanism such that the soil water signal has decayed to the point of no longer being detectable during the data collection time period. 2-D MRI projection images were produced of roots with a diameter range of 1.5–2.0 mm using an image acquisition time of 15 min with a pixel resolution of 1.74 mm in four soil types. In addition, we demonstrate the use of a data-driven machine learning reconstruction approach, Automated Transform by Manifold Approximation (AUTOMAP) to reconstruct raw data and improve the quality of the final images. The application of AUTOMAP showed a SNR (Signal to Noise Ratio) improvement of two fold on average. The use of low field MRI presented here demonstrates the possibility of applying low field MRI through intact soils to root phenotyping and agronomy to aid in understanding of root morphology and the spatial arrangement of roots in situ.
- Research Organization:
- Texas A & M University, College Station, TX (United States). Texas A & M AgriLife Research
- Sponsoring Organization:
- USDOE Advanced Research Projects Agency - Energy (ARPA-E)
- Grant/Contract Number:
- AR0000823
- OSTI ID:
- 1615698
- Alternate ID(s):
- OSTI ID: 1799099
- Journal Information:
- Geoderma, Journal Name: Geoderma Vol. 370 Journal Issue: C; ISSN 0016-7061
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- Netherlands
- Language:
- English
Web of Science
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Related Subjects
Agriculture
LF-MRI: Low Field Magnetic Resonance Imaging
HF-MRI: High Field Magnetic Resonance Imaging
MR: Magnetic Resonance
MRI: Magnetic Resonance Imaging
NMR
Nuclear Magnetic Resonance
RF: Radio Frequency
SNR: Signal to Noise Ratio
AUTOMAP: Automated Transform by Manifold Approximation
OD: Outside Diameter
AWG: American Wire Gauge
IFFT: Inverse Fast Fourier Transform
FFT: Fast Fourier Transform