Wheat root system architecture and soil moisture distribution in an aggregated soil using neutron computed tomography

Abstract

Non-invasive techniques are essential to deepen our understanding of root-soil interactions in situ. Neutron computed tomography (NCT) is an example of such techniques that have been successfully used to study these interactions in high resolution. Many of the studies using NCT however, have invariably focused on lupine plants and thus there is limited information available on other more commercially important staple crop plants such as wheat and rice. Also considering the high neutron sensitivity to hydrogen (e.g. water in roots or soil organic matter), nearly all previous in-situ NCT studies have used a relatively homogeneous porous media such as sand, low in soil organic matter and free from soil aggregates, to obtain highquality images. However to expand the scope of the use of NCT to other more commercially important crops and in less homogenous soils, in this study we focused on wheat root growth in a soil that contained a considerable amount of soil organic matter (SOM) and different sized aggregates. As such, the main aims of this research were (1) to unravel wheat (Triticum aestivum cv. Fielder) root system architecture (RSA) when grown in an aggregated sandy loam soil (<4 mm) with 4% SOM content, (2) Map in 3D, soil water distribution after a brief drying period and (3) to understand how the root system interacts with soil moisture 2 distribution brought about by soil structural heterogeneity. To achieve these, wheat seedlings were grown for 13-days in aluminium tubes (100 mm height and 18 mm diameter) packed with soil and imaged for the first time at the IMAT neutron beamline (in the Rutherford Appleton Laboratory, UK). To the best of our knowledge, this is also the first study to use NCT to study wheat root architectural development. Our study proved that NCT can successfully be used to reveal wheat RSA in a heterogeneous aggregated soils with moderate amounts of SOM. Lateral root growth within the soil column was increased in regions with increased finer soil separates. NCT was also able to successfully map water distribution in a 3D and we show that large macro-aggregates preferentially retained relatively higher soil moisture in comparison to the smaller soil separates within our samples (Fig. 1). This highlights the importance large macro-aggregates in sustainable soil management as they may be able to provide plants water during periodic dry spells. More in situ investigations are required to further understand the impact of different aggregate sizes on RSA and water uptake. Figure 1: NCT image of a 13-day old wheat seedling root growing in an aggregated sandy loam soil. The colour map indicates water distribution within the soil column.

Controlled Environment Neutron Radiography of Moisture Sorption/Desorption in Nanocellulose-Treated Cotton Painting Canvases

“…The direct interaction between neutrons and hydrogen makes them ideally suited for imaging moisture transport. The study of this interaction has led to a variety of applications and includes soil and plant water distribution, which have been readily imaged. , Other work involved mapping the water uptake and vapor diffusion through wood adhesives . In conservation research studies, neutrons have been used to study water uptake in painting canvases and preparation layers and to visualize the spatial distribution of moisture in paintings .…”

Quantification of root water uptake and redistribution using neutron imaging: a review and future directions

“…The smallest detectable root diameter depends on the soil moisture (determining the transmission signal and the image contrast between root and soil) and the spatial resolution of the respective measurement. For plant containers with a diameter of 3 cm, the detection limit at moderate soil moisture usually ranges between 0.1 and 0.2 mm (e.g., Mawodza et al., 2020; Zarebanadkouki et al., 2019). Much finer roots (e.g., ≤0.05 mm) can be detected using high‐resolution detector setups.…”

Effects of freeze-thaw cycles and soil moisture content on soil available micronutrients on aggregate scale in natural grassland and Chinese pine forestland on the Loess Plateau, China

“…Along these lines, Wang et al (2017b) found that freeze-thaw cycles caused the enrichment of available Cd in > 2000 μm aggregate. Considering the high resistance of soil aggregates, most plant roots grow on the aggregate surfaces, especially the large macro-aggregates (Mawodza et al 2020). The increase and redistribution of available micronutrients caused by freeze-thaw cycles could contribute to the alleviation of available soil micronutrient deficiencies during the winterspring seasons, which would benefit plant growth and quality in the next growing season.…”

“…The volume of water expands during freezing when the liquid water becomes ice, thus increasing the disruption of aggregates, which is likely to increase desorption and release available micronutrients from soil minerals and soil organic matter (Li et al 2008). Therefore, in most cases, the influence of FTCs on bulk soil and aggregate-associated available micronutrients was enhanced by increased soil moisture content, especially in large macro-aggregates, which preferentially retained relatively higher soil moisture (Mawodza et al 2020). Notably, ongoing global warming is decreasing the thickness and duration of snow covers and accelerating the snow melts during winter and spring seasons, especially at temperate regions (IPCC 2007; Makoto et al 2014).…”