Salinity is a major threat to irrigated agriculture. Estimates indicate that one third of all the irrigated lands are already badly affected by salinity or are expected to become so in the near future. How can simulation models help to understand soil-water-salt-plant relationships and explore options for improved management practice?
Traditionally, field trials have been used to analyze and test optimal soil-water-salt-plant practice. However, some important limitations of those field experiments are evident:
- validity is limited to the area and the physical conditions under which the experiments have been conducted
- field trials are often conducted over a short period of a couple of years, ignoring a very important topic in salinity-related problems: the long-term effects
- the number of scenarios to be studied by field experiments is bound to a limit, given practical applications as labor input, available fields, and noticeable expenses
Simulation models can be applied as an extension of field tests to overcome these restrictions of field experiments. Nowadays, well-tested and validated simulation models are available and are ready to be applied to answer questions related to salinity. The SWAP model was used to test the options to understand better soil-water-salt-plant relationships and to explore options for improved management.
Figure 1. Water (top) and salinity (bottom) profiles in the soils resulting from SWAP simulations.
Result and conclusions
The output of the SWAP model has been used to understand processes involved in salinization. Figure 1 shows the water and salt balance in the soil according to conditions with a shallow groundwater and a cotton crop. The impact of different amount of irrigation water and/or different water quality on crop yield and the water and salt balance is presented in Figure 2. These results have been used to sustain research and soil-water-salt-plant management practices.
Figure 2. Impact of water quantity and quality applied as irrigation on crop yields and water and salt balance.
Droogers, P., M. Akbari, M. Torabi. 2001. Exploring field scale salinity using simulation modeling, example for Rodasht, Iran. Irrigation and Drainage 50: 77-90. Droogers, P. and M. Torabi. 2002. Field scale scenarios for water and salinity management by simulation modeling. IAERI-IWMI Research Reports 12.
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