Measurement and heuristic modelling of nitrogen and salt dynamics under Salicornia growing in a hyper-arid region and irrigated with groundwaters of differing nutrient and Salt loadings

Abstract New data highlight the economic value of using nitrogen-rich saline waters, either from groundwater or reject brines from desalination units, to irrigate the halophytic crop Salicornia bigelovii for food, fodder, and fuel in a hyper-arid environment. The greatest benefit was achieved using pressure-compensated drippers. Field measurements of drainage and leaching under the crop showed that all of the salt and nitrogen from the groundwater was returned back to the aquifer as leachate. A simple, heuristic model of groundwater quantity and quality was developed to infer the environmental impacts of irrigating crops with saline and high-nitrate groundwater in a hyper-arid environment. The rise in solute concentration in groundwater is hyperbolic. The parameters needed for this simple model are the fraction of the land that is irrigated, the initial depth of the saturated thickness, the saturated water content, and the annual rate of evapotranspiration. An indicator of the time-rise is the number of years to double the solute concentration. This is Ө A h o /2 ET C , where Ө A is the aquifer’s saturated water content, h o is the original thickness of the saturated layer, and ET c is the annual rate of crop evapotranspiration. The general model is simple and straightforward to parameterise to predict the evapoconcentration of groundwater salinity.