This study has investigated the possibility to monitor simultaneously and continuously the relationship between the macroscopic crop response and the evolution of water content, electrical conductivity and root density along the soil profile during the whole growing season of a tomato crop under different salinity treatments. Water storages measured by TDR sensors were used for calculating directly the actual water uptake by the root system along the soil profile under different salinity levels. During irrigation with saline water the salt content increased along the whole profile but tended to accumulate quite uniformly below 20 cm in the case of the 4 dS/m treatment and at a depth between 15 and 25 cm in the 8dS/m treatment.
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Compared to the reference freshwater treatment, the evapotranspiration under saline treatments started to decrease at a threshold value of soil water EC of about 3dS/m. Based on soil and plant monitoring, the root uptake process was simulated by using a model for water and solute flow in the soil-plant-atmosphere continuum. Hence, the root activity reduction at each depth-node was calculated as a function of the salt (and/or water) stress. This enabled relating the distribution of higher/lower activity of root uptake along the soil profile in response to the actual salt distribution.
