Modelling of soil salinity and halophyte crop production

In crop modelling the soil, plant and atmosphere system is regarded as a continuum with regard to root water uptake and transpiration. Crop production, often assumed to be linearly related with transpiration, depends on several factors, including water and nutrient availability and salinity. The effect of crop production factors on crop production is frequently incorporated in crop models using empirical reduction functions, which summarize very complex processes. Crop modelling has mainly focused on conventional crops and specific plant types such as halophytes have received limited attention. Crop modelling of halophytes can be approached as a hierarchy of production situations, starting at the situation with most optimal conditions and progressively introducing limiting factors. We analyse crop production situations in terms of water- and salt limited production and in terms of combined stresses. We show that experimental data as such may not be the bottleneck, but that data need to be adequately processed, to provide the basis for a first analysis. Halophytic crops offer a production perspective in saline areas, but in other areas long-term use of low quality irrigation water for halophyte production can result in serious soil quality problems. An overview is given of potential problems concerning the use of (saline) irrigation water, leading to the conclusion that soil quality changes due to poor quality water should be considered in determining the areas selected for halophyte growing.

Lysimeter experiment with maize grown under water stressed conditions. Pressure heads are monitored by tensiometers and polymer tensiometers. Soil moisture content is measured by TDR (Photograph: M.J. van der Ploeg).Figure optionsDownload as PowerPoint slideHighlights
► Valuable empirical understanding of crop responses to drought and salinity stress are available, but are difficult to extrapolate to other conditions, like soil, climate and salt composition.
► Basic understanding of how to combine drought, waterlogging and salinity stress is still unavailable.
► Despite advances in crop modelling, relatively little has been done to accommodate halophyte crop modelling.
► Irrigating halophytes with saline water may result in serious soil chemical changes that may lead to nutrient deficiency, element toxicity and almost irreversible soil structure deterioration.
► Saline water irrigation of halophytes on fine-textured soils with swelling minerals should be done only after careful impact assessment regarding soil structure deterioration.