Drip & Sub-Irrigation Systems Explained

Drip irrigation supplies water to the top of the soil. Sub-irrigation systems utilize the same components of a drip system, but supply water from within or below the soil. They are both highly efficient systems for greenhouses and outdoor plant cultivation. Other systems such as overhead sprinklers and hand watering produce a lot of wastewater because they are imprecise. Automated drip irrigation and sub-irrigation systems can connect moisture sensors to computerized timers and controllers so water is only applied when needed. Large-scale growers commonly use automated irrigation systems because they eliminate a lot of manual labor and waste less water. 

How Drip Irrigation and Subirrigation Works

Drip irrigation systems conserve water and nutrients by slowly applying water drip by drip to the soil. Whether drip irrigation systems are placed above the soil, or under it, they allow the roots to absorb water slowly with less chance of waterlogging. When properly utilized, drip irrigation delivers water directly to the plant’s root zone with minimal evaporation. 

Advantages and Disadvantages of Drip Irrigation and Subirrigation with Drip Systems

Advantages Disadvantages
Can be used with recycled wastewater (complies with regulations against spraying). Drip irrigation and sub-irrigation systems can be very costly and require knowledge for proper installation and use.
Delivers water uniformly directly to the root zone where it is needed without loss from evaporation. Plant leaves remain dry when irrigated from below the leaves which reduces disease exposure. Drip and sub-irrigation do not accommodate water-activated herbicide use on top of the soil. 
Drip irrigation systems inhibit time-released fertilizers but work well with fertilizers mixed into the water supply. Drip irrigation and sub-irrigation reduce the total use of fertilizer since it is delivered right where it is needed in the root zone. Subsurface systems may not provide enough moisture to germinate seeds sowed at shallow depths.
Water loss from evaporation is prevented by using drip irrigation and sub-irrigation, and water containing chemical fertilizers or pesticides is inhibited from entering groundwater. Drip tape can be damaged by sun and rodents and required extra clean up labor and disposal cost after crop harvest (large outdoor crop application).
Uniform application of water is possible with drip and sub-irrigation systems.
Pulsed drip irrigation systems reduce water usage further because they are even more precise and deliver small amounts of water at regular intervals.
Flexible drip tape accommodates uneven and irregularly shaped growing surfaces.
Soil erosion is prevented through the use of drip and sub-irrigation systems since large amounts of water are not running off the surface of the soil.
Drip irrigation and sub-irrigation reduce weed growth, water costs, and required less labor.

Components of Drip Irrigation Systems

Irrigation tubing can be placed on top of the soil or woven into it. In greenhouses, drip trays can be used to collect any runoff. Runoff should be minimal when systems are properly installed and used, but if present, it can be collected and recycled. Sufficient plant spacing and ventilation are important to ensure plant health when utilizing drip irrigation systems.

  1. Pump or other pressurized water source and water filter (optional) to prevent clogging and remove impurities
  2. Control valves for backwash and pressure (manual or operated by a controller)
  3. Fittings to connect valves, tubes, and hose
  4. Timer or controller for automation(optional)
  5. Hose Types
    1. Distribution Line: Larger diameter pipe that connects to secondary lines and fittings
    2. Lateral Tubing: Smaller diameter polyethylene tubing
    3. Drip Tape: Recyclable and reusable flat plastic perforated hose, available in thin to thick-walled varieties. Thicker versions are best for more permanent placement below the soil. Thinner versions are disposable and good for temporary but high-value crops.
    4. Drip Line: Similar to drip tape but has thin-walled drippers
  6. Emitter/Dripper: Available in various sizes, openings where water exits hose, spray heads are also available
    1. Emitting Pipe: Drip tape with emitters pre-installed
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