Mathematical modelling of water and solute movement in ridged versus flat planting systems

Abstract

Summary We compared water and solute movement between a ridge and furrow geometry and that of flat soil with a mathematical model. We focused on the effects of two physical processes: root water uptake and pond formation on the soil surface. The mathematical model describes the interaction between solute transport, water movement and surface pond depth. Numerical simulations were used to determine how solutes of varying mobility and rates of degradation penetrated into the two soil geometries over a growing season. Both the ridge and furrow or flat soil geometries could reduce solute leaching, but this depended on several factors. Rain immediately after a solute application was a key factor in determining solute penetration into soil. In cases with delayed rain after a solute application, solutes in ridge and furrow geometries collected adjacent to the root system, resulting in reduced solute penetration compared to the flat soil geometry. In contrast, substantial rain immediately after a solute application resulted in ponding where water infiltration acted as the dominant transport mechanism. This resulted in increased solute penetration in the ridge and furrow geometry compared to the flat soil geometry. Highlights We studied solute movement controlled by ponding in ridge and furrow and flat fields. We found the ridged soil could impede or increase leaching compared to the flat soil. Solute hot‐spots formed in ridge and furrow soil because of root water uptake. Time between solute application and rainfall is a key factor for solute penetration.

Significance of root hairs at the field scale – modelling root water and phosphorus uptake under different field conditions

“…We note that the saturation form Richards' equation is valid only for unsaturated homogeneous soil, which applied to the simulation conditions modelled in this paper. Extending the model to either very dry or flooded soils would be possible by using the more complex potential form Richards' equation (Duncan et al 2018).…”

“…where H S (S) is a smoothed Heaviside step function that turns off the flux as the domain approaches saturation (Duncan et al 2018).…”

“…Individual plant roots grow through soil following beneficial mechanical and moisture gradients in order to obtain water and nutrients (Colombi et al 2017;Eapen et al 2005). By applying localized suction around the root-soil interface, plant roots pull water towards them (Duncan et al 2018). Root exudates could alter the mass flow of nutrients as they are known to augment water retention and transport processes (Ahmed et al 2014;, stimulate synergistic micro fauna (Kuzyakov and Blagodatskaya 2015), temporarily reduce soil impedance during growth (Bengough and Mullins 1990;Naveed et al 2017), and even dissolve less-mobile nutrients (Masaoka et al 1993).…”

Rhizosphere modelling reveals spatiotemporal distribution of daidzein shaping soybean rhizosphere bacterial community

“…Analyses of carbon and nitrogen with autoradiography or Positron Emitting Tracer Imaging System revealed the presence of the rhizodeposits within a few millimetres from root surface as well (Holz, Zarebanadkouki, Kaestner, Kuzyakov, & Carminati, ; Kuzyakov & Razavi, ). In addition, advection–diffusion (dispersion) equation has been used to simulate the distribution of mineral ions and water contents in soil surrounding roots (Duncan, Daly, Sweeney, & Roose, ; Vereecken et al, ; Zarebanadkouki, Fink, Benard, & Banfield, ; Zarebanadkouki, Kroener, Kaestner, & Carminati, ). Although the simulation of the distribution of metabolites could provide valuable insights in the rhizosphere interactions, it has not been employed to analyse the distribution of metabolites in soil, at least partly because of the instability of root‐secreted metabolites and the difficulty of the measurement in rhizosphere.…”

Modeling Two-Dimensional Infiltration with Constant and Time-Variable Water Depth

“…Border irrigation was simulated by coupling the Saint-Venant equations and a one-dimensional Richards' equation. Duncan et al [4] presented a mathematical model that describes the movement of water and solutes in a ridge and furrow geometry. They focus on the effects of two physical processes: root water uptake and pond formation in the furrows.…”