The interaction between wheat roots and soil pores in structured field soil

Abstract

Wheat (Triticum aestivum L.) root growth in the subsoil is usually constrained by soil strength, although roots can use macropores to elongate to deeper layers. The quantitative relationship between the elongation of wheat roots and the soil pore system, however, is still to be determined. We studied the depth distribution of roots of six wheat varieties and explored their relationship with soil macroporosity from samples with the field structure preserved. Undisturbed soil cores (to a depth of 100 cm) were collected from the field and then non-destructively imaged using X-ray Computed Tomography (at a spatial resolution of 90 µm) to quantify soil macropore structure and root number density (the number of roots per cm 2 within a horizontal cross section of a soil core). Soil macroporosity changed significantly with depth but not between the different wheat lines. There was no significant difference in root number density between wheat varieties. In the subsoil, wheat roots used macropores, especially biopores i.e. former root or earthworm channels, to grow into deeper layers. Soil macroporosity explained 59% of the variance in root number density. Our data suggested the development of the wheat root system in the field was more affected by the soil macropore system than by genotype. On this basis management practices which enhance the porosity of the subsoil may therefore be an effective strategy to improve deep rooting of wheat.

A holistic perspective on soil architecture is needed as a key to soil functions

“…In recent years, this research has been extended to other faunal groups than earthworms. Once they have been created by various organisms, the geometry and transport properties of biopores can evolve over time when they are colonized by plant roots (Yang, Varga, Liu, & Scheibe, 2017;Zhou et al, 2021).…”

Perspectives from the Fritz‐Scheffer Awardee 2020—The mutual interactions between roots and soil structure and how these affect rhizosphere processes#

“…On the other hand, improved soil structure through connected biopores can have an important role to overcome limitations of plant growth in compacted soil, as roots can grow into them and thus explore larger soil depths (Ehlers et al., 1983; White & Kirkegaard, 2010). In addition, the importance of macropores for root growth increases with depth, as penetration resistance increases with increasing depth (Gao et al., 2016), and thus even under similar bulk densities, root growth is limited to the use of existing macropores in large depth (White & Kirkegaard, 2010; Zhou et al., 2021). Thus, mean penetrometer resistance seems not to be a good predictor for root growth, as it does not include the effect of macropores.…”

Contrasting ability of deep and shallow rooting rice genotypes to grow through plough pans containing simulated biopores and cracks

“…Macropore properties are different in natural conditions as pore walls can be enriched with organic matter from roots of previous crops or other faunal residues (Kautz et al 2013). Naturally structured soils also have a more tortuous and complex macropore structure, so future research on deep rooting by rice should explore intact soils using X-Ray CT to visualise root-soil interactions, following approaches used for other crops (Pfeifer et al 2014;Zhou et al 2021). Recent years have seen a move from flooded rice to AWD (Ishfaq et al 2020), so pan properties may be more important to consider as deep rooting will benefit crop performance (Fang et al 2018).…”