Soil hydraulic properties affecting root water uptake

Various environmental and plant physiological factors play a role in determining root water uptake patterns. The soil physical properties such as the particle distribution affect the amount of soil water available for plant consumption, and the rate of water transfer from soil to root. Climate conditions determine the evaporative demand that is met by transpiring plants primarily through root water uptake. Steep water potential and hydraulic conductivity gradients have been observed in the vicinity of the root surface due to an increase in the flow resistance from the bulk soil to the soil–root interface. In drying soils, the soil hydraulic properties have a more dominant role in regulating water uptake than the physical properties of roots, and the effect of the soil hydraulic conductivity on root water uptake has recently been shown as much more significant than the soil water potential. Compensatory uptake is one example of how root water uptake patterns are controlled by the soil hydraulic properties in suboptimal conditions. The development of both invasive and noninvasive soil sensors has alleviated much of the difficulty in researching below-ground processes, and has enabled imaging of root development and changes in the soil water content due to root water uptake. While much research has been carried out to examine the effect of drought conditions on root water uptake, the effects of other stresses, such as salinity, oxygen stress, and temperature extremes, as well as the combined effect of multiple stresses, are also important topics of research. Root water uptake studies usually focus on fully developed root zones, thereby taking the root density distribution throughout the soil profile as constant. New experiments should be performed to look at dynamic root water uptake patterns as a function of both variable soil conditions as well as a changing root density distribution. Nutrient uptake as affected by the water flow and nutrient transport in the soil remains another important topic of research, and can help in planning fertigation regimes that maximize root water uptake and the resulting crop yields while minimizing groundwater pollution by leachate.