Quantification of water in ginseng roots (Panax ginseng C. A. Meyer) in soil using 3D neutron imaging

The ginseng plant is threatened with extinction owing to the prevalence of soil-borne pathogens and water shortage in field cultivation due to climate change. To optimize water management in controlled cultivation that can sustain ginseng production, a 3D neutron imaging method was developed to quantitatively measure water content of roots growing in soil. It was determined that, according to a Monte Carlo simulation, the neutron penetration rate is 32 %, which allows quantitative measurement of water thicknesses up to 30 mm in aluminum phantom using 3D neutron imaging. In the simulation, the aluminum phantom was buried in soil with 12 % moisture content contained in a 50 mm diameter aluminum pot. In practical experiments, the neutron penetration rate of an aluminum phantom buried in soil with a moisture content of 7.7 % was 18 % at a water thickness of 30 mm. A calibration curve was created to quantitatively measure the water content of aluminum phantom buried in aluminum pot soil with 1.3∼7.7 % moisture. The water content of 3-year-old ginseng roots growing in aluminum pot soil with a moisture content of 7.7 % was quantitatively determined to be 70.0 % (±5 %), 55.0 % (±5 %) and 70.0 % (± 5 %) on the basis of the calibration curve. It is concluded that, the in vivo 3D neutron imaging is a unique way to analyze the hydrology throughout the seedling and culturing stages of plant roots in soil for controlled cultivation. • A 3D neutron imaging (NI) method was developed to measure the water content of plant roots in soil. • 3D-NI is more suitable for determining water content than X-rays, NMR, and 2D-NI. • 3D-NI can be used to quantify the water content of roots and optimize water management of Korean ginseng. • 3D-NI enables the controlled cultivation of root herbs threatened with extinction owing to climate change.