Sub-irrigation (SIPs) = Simple Hydroponics

In a prior post about the TEDxManhattan How to Cultivate a Logo video, I called the TEDx logo planter a hydroponic lettuce grower. How come? As revealed in the video it is clearly a sub-irrigated planter aka SIP (prior posts).

Actually, it’s both. The logo planter is a SIP as well as a simple form of hydroponics without an air pump. If the public is confused by all of the terminology used for various forms of food growing systems it is no surprise.

We have an overabundance of names for a variety of systems for growing plants. Pared down to the basics however, just about all of them are variants of hydroponic growing even though we use different names for them. It is a language and education issue rather than the “engineering” of the methods.

Sub-irrigation (aka SIPs) is an accurate term for systems that use solid (i.e. soil) media contained over the top of a water and oxygen reservoir system. Up to now, I have refrained from calling it hydroponics in the consumer market for a couple of reasons.

1. Hydroponics implies complexity and the need for plug-in power for oxygenation. SIPs are simple to make and do not require power. You do not need to be a rocket scientist to understand how they work

2. In the past, hydroponics has been heavily associated with marijuana growing. I have shopped in many hydroponics retail stores over many years and observed the traffic and the conversation. It is mostly a male clientele and they’re not talking about growing lettuce. This will change over time and these stores will become more family and children friendly.

With the emerging popularity of aquaponics (prior posts), hydroponics is gaining a more family-friendly image. Millions of people will be raising fish and vegetables in home aquaponics systems in the future. Much like the evolution of personal computers and mobile phones, these systems will become more affordable, less complex and user-friendlier. Currently they are not a mass-market product, but I predict they will be.

Back to hydroponics SIPs. These photos reveal what is going on in the hidden zone of a typical sub-irrigated planter. It happens to be a window box SIP that grew lettuce on my fire escape. Obviously, this is a healthy and robust root system. The upper zone in the soil media contains a soil-media root system but look at the mass of white roots that were growing in the water/oxygen chambers. They are “water roots” that have a different cellular structure than "soil roots".

Plants roots are incredibly aggressive in finding water. It is a matter of survival!

Clear SIPs help immeasurably in understanding this. While capillary action is elevating water from the reservoir, the roots are making a beeline down to find it. This is why these systems work so well even when the physical height limitation of capillary action is exceeded.

Only time will tell how affordable aquaponics systems will become. At this time however, various forms of sub-irrigated planter hydroponics represent the best choice for millions of city dwellers around the world.

Photo reveals the inverted (recycled) nursery flat that forms the water & oxygen reservoir. Bottom of fill pipe (recycled water bottle) lower right. The window box is a typical planter found in big box stores. It is too small as demonstrated by the root mass. Wider and half again or twice as deep would be much better.

 

Comments

[John]

Hi, I've been enjoying your site, but I honestly am having trouble really understanding what a SIP is, and how to construct one properly. Perhaps you could address the following:

1)What is the advantage of a SIP, aside from less frequent watering?
2)Is there nutrient solution in the water below?
3)What material do you use for capillary action?
4)Is it not a problem to have roots sitting in stagnant water?
5)What is really going on in the last picture in this post? Is that soil-less root mass below the first visible line?
Are the roots a solid mass, or growing around a plastic planter?

[Al]

Wiki:

"Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk."

Subirrigation is NOT the same. You are not mixing nutrients into the water.

That means all nutrients are derived from the soil. OR you may be using a fertilizer strip. In this case, the soil depth cannot exceed capillary action. Otherwise the top of the soil will dry out & so will your fertilizer strip.