Root growth, water uptake, and sap flow of winter wheat in response to different soil water conditions
How much water can be taken up by roots and how this depends on the root and water distributions in the root zone are important questions that need to be answered to describe water fluxes in the soil–plant–atmosphere system. Physically based root water uptake (RWU) models that relate RWU to transp...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-04-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/22/2449/2018/hess-22-2449-2018.pdf |
| Summary: | How much water can be taken up by roots and how this depends on the root and water distributions in the root zone are
important questions that need to be answered to describe water fluxes in the soil–plant–atmosphere
system. Physically based root water uptake (RWU) models that relate RWU to transpiration, root density, and water
potential distributions have been developed but used or tested far less. This study aims at evaluating the simulated RWU
of winter wheat using the empirical Feddes–Jarvis (FJ) model and the physically based Couvreur (C) model for different soil
water conditions and soil textures compared to sap flow measurements. Soil water content (SWC), water potential, and root
development were monitored noninvasively at six soil depths in two rhizotron facilities that were constructed in two soil
textures: stony vs. silty, with each of three water treatments: sheltered, rainfed, and irrigated. Soil and root parameters
of the two models were derived from inverse modeling and simulated RWU was compared with sap flow measurements for
validation. The different soil types and water treatments resulted in different crop biomass, root densities, and root
distributions with depth. The two models simulated the lowest RWU in the sheltered plot of the stony soil where RWU was
also lower than the potential RWU. In the silty soil, simulated RWU was equal to the potential uptake for all
treatments. The variation of simulated RWU among the different plots agreed well with measured sap flow but the C model
predicted the ratios of the transpiration fluxes in the two soil types slightly better than the FJ model. The root
hydraulic parameters of the C model could be constrained by the field data but not the water stress parameters of the FJ
model. This was attributed to differences in root densities between the different soils and treatments which are accounted
for by the C model, whereas the FJ model only considers normalized root densities. The impact of differences in root
density on RWU could be accounted for directly by the physically based RWU model but not by empirical models that use
normalized root density functions. |
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| ISSN: | 1027-5606 1607-7938 |