The Effect of Salinity On Water and Nutrient Uptake: Field and Model Results.

Shortage of clean water and environmental concerns of groundwater pollution have given rise to measures that have immensely widened the range of water quality available for irrigation. At the extremity of low salinity is the nutrient-poor desalinated seawater and the reuse of agricultural effluent forms the upper boundary of irrigation water salinity. The current state of affairs calls for a better understanding of the effect of salinity and leaching fraction on plant yield and nutrient uptake; modeling of these effects and the resulting composition and amount of water leaching beyond the root zone are essential for decision support.

We evaluated sweet bell pepper growth and production for a variety of irrigation water salinities and water application rates. The experimental setup included twelve 900 liter weighing-drainage lysimeters and 64 9 m² field plots. Plants were irrigated for 250 days with twelve treatments composed of 3 salinities and 4 leaching fractions. The nutrient compositions of irrigation water, drainage water, plant biomass and fruit yield were measured at regular intervals. The measured data was modeled in HYDRUS-1D.

Periodic biomass yield measurements and continuously measured evapotranspiration showed that reduction function parameters for plant response to salinity were variable throughout the season. These parameters are part of a system dependant dynamic process influenced by the feedback effects of nutrient and salt uptake. The HYDRUS-1D model enabled a highly accurate prediction of the amount of Cl^- and NO₃^- in the plant and in the leachate water over time and was demonstrated as a valuable agricultural and environmental decision making tool.