Salt Balance for Halophyte Farming

Growing halophytes using Integrated Seawater Agriculture Systems (ISAS) offers a sustainable solution for the generation of biomass feedstock for carbon neutral biofuelshalophytes do not enter the foodchain and they do not compete with food-crops for natural resources. A field demonstration of ISAS in the coastal regions of Abu Dhabi, UAE, scheduled to start in 2013, will likely face a number of region-specific challenges not encountered in past demonstrations of ISAS at coastal locations in Mexico and Eritrea. The arid climate, unique soil chemistry (evaporite deposits, especially gypsum), and hypersaline coastal hydrogeology of Abu Dhabi will affect long-term halophyte agricultural productivity when Arabian Gulf seawater is applied to coastal soils as part of ISAS. Therefore, the changes in irrigation return flow quality and soil chemistry must be monitored closely over time to establish transient salt and water balances in order to assess the sustainability of ISAS in the region. As an initial phase of the ISAS demonstration project, numerical modeling of different seawater loadings onto coastal soils was conducted to estimate the chemical characteristics of soil and the irrigation return flow over time. These modeling results will be validated with field monitoring data upon completion of one year of ISAS operation. The results from this study could be used to (i) determine the optimal saline water loading that the soils at the ISAS site can tolerate, (ii) potential for sodicity of the soil with saline water application, (iii) impacts of land application of saline water on underlying coastal groundwater, and (iv) develop strategies to control soil water activities in favor of halophyte agricultural productivity.
Figure: (A) Halophytes typically require higher (saline) water loading than conventional crops that require fresh water grown under similar climatic conditions, because the water helps dissolve and flush away any salts that might have deposited in the rhizosphere. (B) The water drains away to the water table aquifer, which usually has a lower salinity than the saline water applied to the crops in seawater farming.