Within the German-Israeli Cooperation, a hydraulic model was developed, that allows accurate prediction of the onset of crop water stress as a function of climate, soil properties and plant traits. The model can be used to schedule irrigation and design optimal hydraulic phenotypes adapted to particular environmental conditions.

Water shortage is a major constrain for agriculture. There is urgent need to identify plant traits that improve root water uptake and irrigation technologies that maximize the efficient use of water.

In the project “Rhizosphere”, we developed a hydraulic model (https://github.com/GERUlab/Soil-Plant-Hydraulics) that allows to calculate the onset of plant water stress. The model has been tested across a broad selection of crops (including tomato, maize, barley, wheat and millet). The model demonstrates that stomata downregulate transpiration and photosynthesis when the relation between transpiration rate and leaf water potential becomes nonlinear due to a drop in soil hydraulic conductivity. This onset of water limitation can be predicted by the mechanistic model as a function of climatic conditions, soil hydraulic properties, and key and root traits such as length and hydraulic conductance.

The model has two practical applications:

1) To schedule irrigation: Optimally, irrigation should start at the critical soil moisture corresponding to the point when photosynthesis starts to drop. This critical point can be predetermined by the model.

2) To identify the optimal root traits for a given soil and climatic environment. Our model is able to determine three key hydraulic traits that largely control crop water use: maximum stomatal conductance, root length and root hydraulic conductance.