Monitoring and modeling root-uptake salinity reduction factors of a tomato crop under non-uniform soil salinity distribution

This study has investigated the possibility for monitoring simultaneously and continuously the relationship betweenthe macroscopic crop response and the evolution of water content, electrical conductivity and root density along thesoil profile during the whole growing season of a tomato crop under different salinity treatments. Water storagesmeasured by TDR sensors were used for calculating directly the actual water uptake by the root system along thewhole soil profile under the different salinity levels imposed during the experiments. It was observed that duringirrigation with saline water the salt content increased along the whole profile but that it tended to accumulate quiteuniformly below the 20 cm in the case of the 4 dSm-1 treatment and at depth between 15 and 25 cm in the case of the8dSm-1 salinity treatment. Compared to the reference freshwater treatment, the evapotranspiration under salinitytreatments started to decrease at a threshold value of the time-depth average electrical conductivity (EC) of soil waterof about 3dSm-1. Based on the results of soil and plant monitoring, the root uptake process was simulated by using amodel for water and solute flow in the soil-plant-atmosphere continuum. This way, the root activity reduction at eachdepth-node was calculated as a function of the salinity (and eventually water) stress. This enabled relating thedistribution of higher/lower activity of root uptake along the soil profile in response to the actual distribution of salts.