Subsurface Irrigation
Practice Overview
A subsurface irrigation system acts as a comprehensive water management tool, functioning as both a controlled drainage solution and an irrigation system. Using the same pipes used to remove water from the field, a subsurface irrigation system supplies water from a well, ditch, storage pond or other source back into the drainage pipes to deliver water directly to crop roots. This approach ensures the water table is always at an ideal level through drainage of excess water from rainfall and precise subsurface irrigation during dry periods.
Benefits
Subsurface irrigation systems are highly effective at delivering moisture to crops during dry spells. With the added benefit of controlled drainage, this system gives farmers the ultimate control over the water table in their field. There are various benefits for installing a subsurface irrigation system, including:
- Higher and less variable yields
- Reduced nutrient loss
- Less energy and water needed to irrigate compared to other irrigation systems
Components of a Subsurface Irrigation System
Subsurface irrigation systems are made up of the following:
- Drainage system with laterals and main
- Water level control structures
- Water source (e.g. ditch, storage pond)
- Pump
- Irrigation supply lines
How It Works
In a subsurface irrigation system, water is supplied from a pond, well, or other source and pumped back into water control structures. This water flows into the main and lateral pipes, raising the water table to a predetermined level to deliver moisture directly to the crop’s root zone. The water essentially fills up the system to the level of the water control structures. A combination of floats, pumps and automatic valves can be used to monitor and optimize the system.
Since water isn’t pumped overhead, subsurface irrigation systems avoid significant evaporation loss that occurs with above-ground sprinkler irrigation on hot, dry days. This method allows the soil profile to act as a reservoir, offering efficient management of crop stress while maintaining the ability to drain excess rainfall as needed.
Installation Considerations
- Most effective on flat fields
- Lateral spacing should be about 65% closer than traditional drainage
- Soil must have high water holding capacity
- Soil profile must have an impermeable layer to prevent deep infiltration