Saturday, January 9, 2010

Results in Roof Growing 2009: Emptying Your Sub-Irrigated Planter

In this link, we show you how to make a two-bucket SIP, or sub-irrigated planter. But what happens when the growing season ends?

You pull the top bucket out and get to view plant behavior underground. In this photo, the lefthand bucket grew greens with shallow roots. On the right, a tomato.

Note the tomato roots have plunged all the way down
to the wicking cup
and out its slits into the water reservoir.
This year we tried something new with buckets. While a majority of our SIPs are made from 5-gal in 5-gal recycled food-grade buckets, last spring Art ordered a bunch of 6-gal and 7-gal food-grade buckets to make sets with larger reservoirs.

Click the photo to see the height of the overflow hole
in these 5-gal SIP sets.

Now check the height of the overflow hole
in this 6-gal in 7-gal set.

We haven't measured exactly how much more water the larger bucket set holds, but it's considerable. You don't need a larger bucket set. It just cuts down on the frequency of watering at the height of summer, especially for the heavy drinkers, tomatoes and eggplant among them.

We also wondered if these same veggies might benefit from the extra space for growing medium--obviously more potting mix fits in a 6-gal bucket than in a 5-gal bucket. I'm not sure we saw any difference, but summer weather was very odd this year so it's tough to compare.

I thought you'd be curious to see the root system in the larger buckets. To make the wicking cups for the larger SIPs sets, we used recycled two-liter pop bottles with the top cut off and slits downs the side.

Look at the density of eggplant roots
in the two-liter wicking cup.

These ropey eggplant roots
know where to head for water.

A long view.

The Official Earthbox™ Planting Guide says you can re-use potting mix year after year without emptying the boxes, but I don't do that with my two adopted earthboxes. I believe any type of SIP needs emptying, airing, and drying out to limit the chance for disease.

With bucket SIPs, because the plants so completely occupy the growing space, you need to extract the roots at season's end and toss them away to compost somewhere. Your goal is to pull out as much of the organic matter as possible.

Pulled root mass with potting mix
shaken off for re-use.
We combine used potting mix with fresh mix in a large bin and use it again to plant the following spring. Our blend contains mostly peat and perlite with a little coir. Mea culpa: we're going to try to use less peat next season and boost the coir--coconut fiber that's vastly more renewable than peat.


Jeff Vandiver said...

Could you tell me where Art ordered those 7 gallon buckets? I'd like to find some pretty cheap. Thanks!

H2 said...

Hi Engineered:
The buckets came from US Plastics, link below.

I should also note that I mis-identified the bucket size and am fixing above. For the larger sets, we used 6-gal in 7-gal SIPs.

Jeff Vandiver said...

h2 - thanks! i'll check that site out.

Unknown said...

Pretty big roots, no wonder you got so much tomatoes :)

LeAnn said...

This looks great. I've never seen anything like this.

H2 said...

It's an easy way to grow your own food, LeAnn. Check out the tutorial in the upper right column if you want to try it.

LeAnn said...

OMG! Now that I read enough to understand what you guys are doing, this is awesome. I seed start in my greenhouse and garden in raised beds with a drip system, but I see the benefits. I even think I know someone who has done it! Last summer, I watched a guy down the road plant in buckets. I thought he was crazy because he would never keep them well watered during warm days, but was surprised to see healthy plants at the end of summer.

H2 said...

Thanks much for your comments and enthusiasm. January is a perfect time to make some SIPs, ahead of the growing season. Now you can ask the guy down the road if he's using this system...