Sub Irrigated Raised Beds experiment

[Dudeness]

Hello gardeners! I am still new to gardening in north Texas, 2019 was year 1 for me and it was a huge eye opener compared to the gardening I had been doing in Nebraska. The biggest issue, water. In NE, I could easily get by on rain and a 55 gallon rain barrel, but here, we can easily go 4 or more weeks with no rain and 100+ temps. To avoid the miserable native clay, I installed raised beds. So far, I can keep my plants alive through the summer, but they certainly aren’t thriving.

This year I am converting three of them into sub irrigated beds. The theory sounds great, having a reservoir in the bed to keep more consistent moisture through the bed. So I am putting in a small pond liner into the bottom of the bed, placing some pots with holes in the bottom into the base, and about .5" of pea gravel. Then I wrap in a corrugated drainage tube (the ends of the tube are covered with landscape fabric and zip-tied to the tube). A hole is cut into the top and a piece of 1.5" PVC is slipped in on one end to be used as a fill tube (the inserted end is cut at a slant with holes drilled into it around the bottom 2"). Then to the other end, a smaller hole is cut in the tube as well as the bed. This smaller hold is for a 3/4" PVC tube that is for drainage (don’t want standing water getting up to the soil). The pots are then filled with sand, and I add in some drainage rocks to the void space to fill up about 3/4 of the way to the top of the drainage pipe. I then add in sand to be about 1/2" above the pipe. This all acts as the reservoir and the sand should wick the water upwards.

From here I found conflicting opinions if you should put down landscape fabric or not. I am opting not to, and then top off the bed with about 6-8" of potting mix. Once I get my initial plants in, I plan to put some mulch on top to help keep evaporation down.

Does anyone have experience with sub irrigated beds? Any advise or opinions on making the system better? I know that for initial plantings and seeds I will still need to water the top of the beds, but my goal, is that by the time the drought gets here, I won’t need to top water and I can just fill the reservoirs once or twice a week.

[marknmt]

Sounds good. It’ll be interesting to learn how it works out. I know that with my raised beds keeping them watered is an issue.

[Dudeness]

Here is what i have so far. The three up front will be the sub irrigated beds, 2 of them are essentially done, with the one on the right in progress (too muddy right now to finish digging to get it level.

Here is the tube that i lay out in the bottom with landscape fabric coving the end:

and finally, i have planted out one of the beds with lettuce and bok choy on one end and radish seeds sown on the other end.

[JimmyM]

Wow! Fancy raised beds. Corrugated steel? That irrigation setup looks like it should work awesome. How deep to the top of the pipe?

[Dudeness]

yes on the steel. Cedar at the local lumber yard and big box stores was getting pretty pricy. This was only a few dollars more per bed, and should last longer (I will be kicking myself if it doesn’t). it should be about 9" from the top of the soil to the top of the pipe.

[Dudeness]

Just an update here, got some of the beds planted out. So far no real difference between the sub irrigated and the standard raised bed, but I kind of expected that, the key is it should do better in the summer time heat and drought.
Sub:

Reg:

Almost time to start harvesting some bok choy and lettuce.