*Disclaimer - The following statements explain my thoughts on how to control the soil moisture content in a homemade self-watering container/self-watering planter, and by no means is the only method for addressing this issue. I only wanted to share what works for me, and certainly do not claim to be omnipotent on the subject, or the "messiah of swc's/swp's." I do not expect credit for any discoveries made, nor do I intend to someday become the leader of a "following" from those that would be helped by my methods. This is what works for ME, and I live by showing - rather than telling. I do not name my swc/swp designs to make them stand out, nor do I place pictures of them onto every gardening forum on the internet. These are my thoughts, of which are freely shared with anyone that might accept them as useful information for their gardening experience.
A few years ago, I stumbled upon a growing movement of gardeners online that displayed pictures of various homemade self-watering containers that they had designed, which grew some of the best looking vegetable plants i'd ever seen grown in a container. Tomatoes, corn, peas, squash, and even pumpkins did well in them. So, I joined the movement by building several of the more popular designs on the 'net. I even told my dad that this would provide the means for growing the most beautiful tomato plants he'd ever seen. Boy...I was excited about it, to say the least.
Little did I know, that each and every design had a major flaw - which was the fact that the excessive wicking characteristics of the soil was to the point that tomatoes would achieve less than ideal results (especially in a humid environment such as mine). Blossom end rot and radial cracking of fruit became so rampant, that I personally considered the end result a complete disaster. So, being the highly educated, analytical (but bonafide redneck) person that I am, I set out to find an answer to the problem that had previously eluded all other self proclaimed swc "experts".
Rather than flooding the internet with an ever-changing design of what worked better (like Rev. 3.1, 3.2, etc.), I opted to run trials and experiment with various ways of controlling the water movement from the reservoir to the mass of soil where the plants live. In other words - I was done listening to people that obviously had more money then sense, because they had done nothing but steered me in the wrong direction, and I decided to use my knowledge and common sense to hopefully succeed where others have repeatedly failed. Being a pretty nice, sensible guy, I even attempted to give input to those that were still seeking the answers - only to be shunned and barely acknowledged. So, I was pretty much on my own, and am considered a "thread killer" anytime I post to one of the threads started by one of the more popular members of Gardenweb....
What I discovered, was that a certain sized orifice between the water reservoir and soil mass would meter the water in such a way that you can literally alter the soil moisture level to fit your needs. Some think that the soil mixture should be altered to control capillary action, but the ingredients are not readily available to everyone in different parts of the country. So, my test was performed with a growing medium that is readily available to all people that have a big box store close by. That would be Miracle Gro potting mix.
With a single 7/64" hole drilled into the wicking cup of my little 4 gallon swp constructed from 2 cat litter buckets, a broccoli plant was grown to maturity in the fall of 2009 with excellent results.Soil moisture was consistently regulated to a reading of 3-4 on the moisture meter, which is right at the beginning of the "moist" range. At that point, I knew that my orifice reduction had worked.
Still, I set out to come up with my own soilless mixture that would enhance the situation even further, by using bulk ingredients to duplicate the highly touted "ProMix BX" growing medium that had brought so many people excellent results in commercially sold Earthboxes. ProMix BX is good stuff, but expensive!
So, I came up with what I call "6:3:1", which is 6 parts peat moss/3 parts perlite/1 part vermiculite. Purchasing the ingredients in bulk is really cheap, and you'd be surprised how many containers can be filled with only $40 worth of stuff from your local farmer's cooperative...
Anyway, here's the following measurements gathered the other day from several of my swp's/swc's currently in service.
Photo below - 16 gallon swc with three 7/64" holes drilled into the bottom of a 6 oz. yogurt cup being used as a wicking basket. This particular swc is being used to grow honeydew melons.
Photo below - 4 gallon swp constructed from a single 5 gallon bucket (as seen on my blog), with a single 7/64" hole drilled into the 6 oz. wicking cup. An early girl tomato plant is being grown in it, and the reading was taken just a few days after the reservoir was initially filled with water. I'll recheck in a few days to see if it has come up any, and would love to get a reading of around 3.5 to 4.
Photo below - 34 gallon swc that has 2 margarine bowls evenly spaced for wicking baskets, and has three 7/64" holes drilled into the bottom of each one. A total of 12 cucumbers are currently planted in here, and the reading of 4 is pretty good, in my opinion.
Photo below - here's a 31 gallon rubbermaid tote with a 9"x 9" pond basket in it for the wicking basket. To reduce the "water to soil" effective area, the entire pond basket has been sealed with foil tape - then eight 7/64" holes punched through this tape for metering the water into it. I'm happy with this reading, as corn is currently being grown in it.
Photo below - Finally, here's one of my swp's constructed from 2 cat litter buckets, and the same single 7/64" hole is being utilized in this planter, too. I have a couple of cucumbers in here, and expect them to do rather nicely.
Since the 4 remaining swc's were just recently planted with tomatoes and filled with water, i'll let them settle for a week or two before taking any readings. They are of course 31 gallon rubbermaid totes that are being used to grow heirloom tomatoes in, and will be the most interesting to watch - to say the least. In reality, they are the biggest concern for me, because this will be the first trial run for this particular wicking basket/soil mixture setup. In the end, i'll certainly show the results - whether they will be good or less than ideal.
*After using them for the season, the mix and orifice combination worked out very well.....
*Update on 6/5/11
My thoughts remain the same toward the mixture being used, but I have incorporated some pine bark (about 2 parts) into each swc for the 2011 growing season. The reason is to increase drainage to offset any heavy rainfalls from over-taking the moisture control so diligently strived for - as well as more airspace into the root zone.. As you might imagine, new growing experiences have brought with them more knowledge about the subject, and incorporating more oxygen into the root zone is what i'm trying to achieve at this time.
I also understand that certain configurations provide different results in various parts of the country. In other words, what works in the Pacific Northwest won't give the same results here - and vice-versa.
Even though I have 20 swc's/swp's currently planted for the 2011 season, my preference of gardening methods would probably be a deep raised bed with the right soil mixture in it. It's much easier to maintain, has less problems with blossom end rot, and certainly looks much better, too.
However, if anyone reading this is contemplating building some homemade swc's for yourself, I hope that the contents of this post will help you in some way. My advice to you is to learn all that you can by reading about other's experiences/trials, then determine what combination works best for you in your location.
Take care, and happy gardening!