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Back 2 Basics Part 7!

© a.k.a. MBR

The term "sub-irrigation" describes the vast numbers of hydroponics growing methods which focus on increasing their production efficiency by delivering the required nutrient solution directly to the plants' roots; "sub" referring to the application occurring under or below the media surface (in the rhizome).

The delivery of the solution directly to the plants' roots can dramatically decrease the amount of water lost through evaporation, thereby increasing the dry weight to evapo-transpiration production yield ratio.

Many different styles of hydroponics growing fashions involve variations of sub-irrigation techniques and could be classified as such, but this article is specifically oriented towards describing the use of such items as "soaker"-hoses, drip-lines, etc. that are implanted below the surface.

Sub-irrigation systems are usually designed in a similar way as to the previously described hydroponics drip systems in that the delivery apparatus is designed to move fertilizer nutrient solution from a reservoir to the plants roots as efficiently as possible. This usually involves the use of a pump and various types of delivery lines. Please refer to the diagram that shows a basic configuration.

Recently polymers and other new materials have been developed that allow for inventions such as micro-pore tubules and precision drippers that can be useful depending on circumstances.

The main benefits of using the various sub-irrigation techniques are the increased water conservation potential requirement during nutrient delivery and the ability to have optimal control over nutrient and water utilization.

Drawbacks of sub-irrigation arrangements can be the variability in uniformity with time due to sub-surface root blockage and salt buildup, and the detrimental implementation complexity associated where large plant numbers are to be grown. Some manufacturers are supplying emitters that have been treated with pesticide to prevent root blockage. Blockage can be prevented using mechanical barriers and maintenance.

Sub-irrigation can also be difficult when using any insoluble or particulate or organic nutrients and/or supplements due to the possibility of clogging occurring.