Optimizing Irrigation

The main irrigation performance indicators are distribution uniformity, adequacy, application efficiency, and irrigation efficiency. They evaluate different aspects of the irrigation process and have to be used jointly for a comprehensive assessment. A simple model combining the spatial distribution of irrigation with the biomass-transpiration relationship allows the calculation of optimum irrigation amounts. For cheap water, optimum irrigation will seek maximum yield and will depend only on uniformity and the irrigation requirement. As water prices increase, economic factors play a key role in the calculation of optimum irrigation. Irrigation uniformity has a large impact on the spatial variation of N uptake and losses. Conventional N fertilizer applications will lead to higher N losses than fertigation, which can be quantified. The key parameters in the design and management of irrigation systems are the seasonal irrigation requirement and the peak irrigation system capacity. In locations with dry summers, the variability of the seasonal irrigation requirement depends only on rainfall variations, and the variability of peak irrigation is negligible. The dose of irrigation events can be calculated following similar rules for all irrigation methods.