Subirrigation: a good way to provide containment

JJohn W. Bartok Jr.

Q: Sub-irrigation: a good way to provide containment

There are several areas of concern covered under runoff regulations, including water from greenhouse roofs, runoff from driveways and parking areas, excess interior irrigation water and leaching from exterior growing areas. Subirrigation is one method that contains irrigation water. Instead of letting leachate drip from benches or ground beds into the soil, the water is collected, stored and recirculated.


Containment advantages
Besides the benefit of reducing runoff, there are several other advantages:

• Less labor. Most of the time needed for the setup and operation of an irrigation system is eliminated.
• Uniform plant growth. Every plant gets the amount of water it needs.
• Less water is needed. A savings of 50 percent or more of water can be realized.
• Less fertilizer is needed. Without leaching, fertilizer rates can be reduced by 25–50 percent.
• Lower humidity. Because the foliage remains dry, there is less evaporation.
• Less disease. As there is little water movement between containers, spread of disease is limited.
• Increased space efficiency. With the use of bench and floor systems containers can be spaced more efficiently.

Containment system concerns
Challenges to ebb-and-flood irrigation include:

• Greater system cost. Depending on the system installed, cost can be $10-$20 per square foot of growing area.
• Learning curve. Production techniques are different than conventional production with overhead irrigation.
• Greater monitoring of irrigation solution. Electrical conductivity and pH have to be monitored on a regular basis.