  Irrigation decision systems and water need models have been important
research topics in agriculture since 90s. They improve the efficiency of crop
yields, provide an appropriate use of water on the earth and so, prevent the
water scarcity in some regions. In this paper, a comprehensive survey on water
need models depending on crop growth and irrigation decision systems has been
conducted based on mathematical maodelling. The following outcomes and
solutions are the main contributions. Crop growth models and correspondingly
water need models are suffer from un-modeled dynamics of the environment and
lack of sensory devices. Literature review with the latest developments on
water need models, irrigation decision systems, applied control methods and
discussions are expected to be useful for the future strategies.
