Below the surface: using soil moisture observations and simulations to optimize installation and operation of subsurface drip irrigation systems in southern Alberta

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Subsurface drip irrigation (SDI) is an extremely water-efficient irrigation technology that delivers water at very low rates right into the root zone where plants can take it up. SDI systems can be used on irregularly shaped fields, can be fully automated, and can deliver nutrients as well as water, which creates an opportunity to increase crop yields without increasing water use. These aspects of SDI systems are fueling an increasing interest in SDI technology in southern Alberta. Lethbridge College and Southern Irrigation are partnering in a project that explores management of subsurface drip irrigation systems in terms of water and nutrient use efficiency. **The project combines laboratory, field, and computer experiments. In the extensive laboratory experiment, we will construct three wooden bins with common southern Alberta soils and seed alfalfa as a test crop. In each bin, two SDI systems with different emitter spacing will be installed at two depths for a total of four systems per bin. We will evaluate the ability of each system to deliver water to the crop under various irrigation management schedules with > 40 soil moisture sensors. In a second phase of the project, we will also evaluate the ability of the SDI systems to deliver P fertilizer to the crops. The insights gained in the laboratory experiments will be applied in the irrigation management of SDI systems in real fields during the growing season of 2018. Complementary computer simulations will help us explore what-if scenarios of irrigation water management in soils and weather conditions other than those experienced in the lab and field. The large setup in the laboratory creates a unique opportunity to test an irrigation technology destined for field crops in an indoor setting. Because of this, we can run experiments outside of the growing season and experiment with a large range of water management schedules without compromising a producer's yield and profit. The integration of the laboratory, computer model, and field results will allow us to generalize our findings into better SDI installation and management strategies for producers in western Canada. **********