Thursday, January 12, 2012

A Little Winter Project....

Building an Inexpensive  Capillary Mat Table

As part of lowering the inputs the Farm has been purchasing, we have made a conscious effort to eventually move all our seedlings and transplants into the soil block system instead of plastic plug trays.  Soil blocks have many long term advantages (I'll post on this at a later time) but one of the issues always bugging us was the use of overhead watering and the effect on the block from dripping water before the plants reached a size that block integrity wasn't impacted by overhead watering.  

So we decided to build a  Capillary Mat Table.  Our propagation house is a small and unheated hoop house with  two 4'X16' tables inside.  We decided to take one of these existing tables and convert it to a Capillary Mat Table to grow the soil blocks on for 2-3 weeks before moving them to another area with overhead watering to finish them off before field transplant.

 The picture to the left shows the basic table. Real basic..hog wire panel, posts & blocks for support.  Each table also has a drip mister setup for automatic overhead watering. we also use a black 3/4" polypipe set of hoops to suspend our frost protective Agribon.

To create a flat insulating and somewhat water resistant base to the capillary mat, we chose to use 1 5/8"Styrofoam insulation board.  This is sold in 4X8 panels at most hardware or home center stores and goes for about $17-18 per panel.  For this table we purchased two panels.  We cut the panels into 4X4 size mostly for ease of transport and table installation.
From this view we have laid down approximately half the base of the table. Each panel is adjusted with a cut out for the drip misters and the hoops to suspend Agribon fabric cloth for frost protection.  For extra stability we put some thin wood stripping under the panels on top of the hog wire base.
This shot shows the the base of the table down and the hoop and mister cutouts completed.  The next step is attaching a wicking water source to feed the Capillary Mat.

What we decided on was to use an inexpensive vinyl gutter.  We purchased this 10' gutter and ends for about $12.50.  The bottom of the gutter is supported by four  2X4 braces with the top of the gutter attached directly to side of the table using basic dry wall bugle type screws.  The gutter is centered so that only 3' of the table at each end does not have gutter next to it.  Note the roll of Capillary Mat in the background.  The cheapest I found was at Farmtek 4'X100' roll was the smallest size, delivered cost was $116 or about $.29 per sq ft.   
The mat was rolled out to a 16' length then cut from the roll and folded in half on the table.  The next step was to cut holes in the mat for the misters and for the Agribon hoops on the edges.  

The next step was to cut the mat which wicks from the water source to the table mat.  I cut three 2' lengths from the 4' roll of mat. One of the pieces I re-cut into a 2X2 piece.  The three pieces in total now will fit the length of the 10' gutter.   We then laid one end of each piece about a foot and half under the table's mat, with the gutter end covering the bottom of the gutter.  Note the mat cut outs for the hoops.

 The table is now complete and ready for loading! The total cost of this table was $39 for the insulation board, $12.50 for the gutter & $25.50 (cost of mat used on table only) or about $77 total, $1.20 per sq ft.  If you include the cost of the total roll of capillary mat then total out of pocket cost for this is $167.50.
So let's fire this Bad-Boy up! 

We add water to the wicking tray and we manually apply water to the top of the mat on the table to get it good and moist.  The wicking action depends on the moisture in the mat being drawn into the soil blocks.  This pressure draw allows the wicking water in the gutter to be "pulled" through the mat to the plants on a continuous basis.  We then started putting the trays down on the mat. Its important that the trays lay as flat as possible on the mat giving maximum contact between the blocks and the mat.

So that is it! It took about 2 hours max. to get this table up and  rolling(depending interruptions.)  Now we can get even watering of our plants for those critical early stages of growth and transplant.  As part of our philosophy of keeping what we do transparent to all who follow us or buy from our sustainable farm I'm glad to answer any question. You can contact me at

Tony Gaetz


  1. Dang, what a great idea!!!
    I too hate all of the plastic trays.This looks like a really neat solution.
    As always thanks for sharing your great tricks :)

  2. Neat idea! I'm glad I found your blog, I enjoyed your stand at the Saturday Market in Corvallis this summer. Thanks!

  3. Thanks for the kind words! We will report how well it works in the next few weeks as we load it up with seedlings.

    ErikaJean - We will be back in the Corvallis market for our 10th season this year, stop by and say Hi. We would love to meet you!

  4. You two are always coming up with great solutions to farming problems! I'm so inspired! I was already planning to build a "hot box" (was in Growing for Market recently) in my hoop house to use for germinating trays and now I think I'll add this concept to the plans as well...that insulation though may keep the heat from below rising up into the trays. Do you think the capillary mats would work just as well if I left some cracks between the insulation for heat to rise through? Or perhaps I could drill holes...? What are the bottoms of the trays like that you are using to hold the soil blocks? Mesh, grid, solid? Seems like that would make a big difference for the wicking.

    I couldn't tell from the photos - how are the hoops kept in place? I was thinking some big nails pounded in the table would do the trick but would love to know what Tony's come up with. :-)

    And finally, while I'm picking your brains, can you pretty please report back on how often you have to fill the gutter with water? Another challenge for me is that I don't live on my farm so regular watering of seedlings has been a bit challenging. Would love to know if this system could get them through a day or two without my help.

    Thank you!!!

  5. Hi, I found you on Erin's blog. I've been considering soil blocks and your post has me solidly convinced! I'm looking forward to browsing through your old posts - I'm new at this, and in a totally different climate. I so envy all the things ya'll can grow way out there!

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