Modeling potato root growth and water uptake under water stress conditions

Potato (Solanum tuberosum L.) is considered a drought sensitive crop. Accurate simulation of root growth is critical for estimating water uptake dynamics. However, data required to build and test advanced potato root simulation approaches is lacking. Previously unpublished data from our soil-plant-atmosphere-research (SPAR) chambers was used to evaluate a new two-dimensional diffusive root growth module linked to the existing potato model SPUDSIM. The root module consisted of diffusive parameters controlling the direction of root growth in horizontal and vertical directions, and an additional convective term for vertical growth within the soil. This modified SPUDSIM was tested against observed SPAR data which consisted of root distribution in the soil profile and organ dry weights (DW) at harvest, plus daily water uptake patterns for each of six different irrigation treatments. The difference between simulated and observed DW data was within two standard errors for most plant organs-root DW was over-predicted for well-watered plants. Spatial and temporal patterns of root distribution and water contents were reproduced well. However, the model tended to over-estimate water uptake from soil layers closer to the surface. Differences in simulated root growth patterns among irrigation treatments were the result of fluctuations in soil water status, bulk density, and root density which, in turn, affected the amount of carbon allocated to the roots in different soil layers and the value of the convective term. These results suggest the new module will provide more reliable predictions of potato water uptake for improved agricultural decision support tools.