OLD : Olla Irrigation (Clay Pot System)

We've been inspired by Fan Sheng-chih Shu. His writings from the first century BC describe a method of irrigation where a unglazed clay pot is buried in the soil. When filled with water the clay pot turns into an amazing high-tech device. The micro-pores of the clay pot allows water to seep into the surrounding soil. A key characteristic is that the water seepage is regulated by the water needs of any nearby plant. When the plant's water demands have been fulfilled and the soil is moist, the water seepage from the clay pot will stop. When the soil becomes dry, water seepage will begin again. This seepage is controlled by soil moisture tension. It's automatic irrigation without timers or electronic sensors!

Water Efficiency Combined with Liquid Fertilizer
Some designs (see below) allow you to bury the olla in the soil or potting mix. This allows the delivery of water directly to the plant's roots. No water is wasted. This is excellent for arid climates like in many parts of Africa. Finally, you may supply the olla with water mixed with liquid fertilizer. You'll only need about 1/4 to 1/2 of the fertilizer you would normally use. Although liquid fertilizer is more expensive than granular, it may end up costing less because of the tremendous efficiency of the delivery of the fertilizer directly to the plant's roots.

Combining Ollas with Global Buckets
Only one bucket is required and the use of power tools for drilling and cutting of buckets is eliminated. It's much more fun to caulk (required for clay pots) than to drill. We've begun (summer 2010) the testing of ollas in Global Buckets. So far we've had excellent results.

How to build your own Olla Global Bucket system:
Step 1: Build the clay pot. It's easy! Just glue two unglazed flower pots together.
Step 2: Bury your clay pot into a bucket with just the top of the clay pot exposed. Use potting mix with dolomite.
Step 3: Keep the clay pot filled with water. After a month of hand watering (boring!), we're designing an automatic watering system (see below).

Step 1: Build an Olla
Seal the hole in what will become the bottom section of the clay pot. We bought a ceramic floor tile from Home Depot for 99 cents and broke it up into little pieces. Apply lots of waterproof silicon caulk around the opening and then stick a piece of the broken floor tile over the hole. We also caulked the other side (pot's exterior) of this hole with more silicon caulk just to ensure that leakage won't be a problem.




Next you'll need to attach the two clay pots together.

If you're using Gorilla Glue (as we do) you'll need to lightly wet one of the pots as shown in this picture.







We first use 100% waterproof Gorilla Glue. We let the Gorilla Glue dry overnight. We then put heavy amounts of silicon caulk over the connection (the Gorilla Glue leaves lots of tiny gaps). The end result is not very pretty, but it's watertight!






The finished product. We painted the top of the Ollas that will be exposed to sunlight with white paint. Since the top is now painted or glazed, evaporation will be greatly reduced. We learned this the hard way.






If you click on these pictures to enlarge them, you'll see where the potting mix is moist from the olla.

Ollas (Clay Pots) in Developing Nations
This is an excellent Phd thesis from a student at the University of Pretoria on the use of clay pots in developing nations. Lots of great information.

This research paper is from the OAS (Organization of American States). It also relates to clay pot's use in developing nations.


Automated Olla Irrigation
(Note: We're still testing this design. No guarantees of success.)

Newest Design : 6-29-10 : Still Testing.....
The goal of this design is simplicity, leak-free smaller ollas and gravity feed (no siphons).

Materials:
a) 1/4" poly pipe
b) 1/4" "T"
c) 1/4" x 1 1/4" Fender Washer
d) Silicon Caulk
e) Plumbing Epoxy Putty (it's waterproof, easy to handle and safe for humans)
f) Terra Cotta Pot and Saucer


We used plumbing epoxy putty for everything, except when we used silicon caulk to attach and seal the saucer to the pot. We used two brands of plumbing epoxy putty. In the pictures, one brand is white and the other is gray.
That's white silicon caulk between the pot and saucer.

This week we'll attach a series of these ollas to a gravity fed 55-gallon barrel for the final testing.



1st Attempt at Automated Olla Irrigation
Result : Leaks!
There appears to be some water leaking where the 1/4" poly pipe enters the 7/32" holes. We're beginning to believe that the silicon caulk doesn't adhere 100% to the slick poly pipe. We are looking into alternatives.










We've modified most of our clay pots to implement our automatic clay pot water refilling system.

Step 1: Drill two holes in what will become the top section of the clay pot. Do this before you glue the two pots together. Use a 7/32" concrete drill bit. Later you'll be inserting 1/4" irrigation tubing into these two holes.

Step 2: You will also need to seal the the top drain hole that exists in the original pot. Do this before you glue the two pots together. Seal it like we sealed the bottom hole (ie silicon caulk and broken floor tile).

Because we modified our top pot after they were glued together (not recommended) they're really ugly!

A 4" clay pot is buried. One 1/4" tube is the water feed. The second 1/4" tube allows air to flow out when the pot is filling with water. Once the clay pot is filled with water, water travels through this second tube to the next clay pot in the series.

The 4" olla is completely buried.









This is a 6" olla. It takes up a large amount of space. We were unable to completely bury it.










This post will be updated throughout the summer of 2010 as we implement the olla system in Global Buckets.

Experimental Design : Colander

Colander Design using One Bucket (click on pictures to enlarge)

You'll need:
A) colander (plastic and approximately 10 1/4" in diameter)
B) 1" PVC (24" in length)
C) 5-gallon bucket (only one is needed)
D) 1/2" poly irrigation pipe (2' length)
E) plastic cutting tools (Best: Drill with 1 3/8" & 3/4" hole saws, Alternative: razor knife, metal shears)


4 Easy Steps to Build
1. Go to a discount store (eg Dollar Tree) and buy a plastic colander with an approximate 10 1/4" diameter (10 1/4" is the width at the bottom of a typical 5-gallon bucket) for about $1.00US. Cut the protruding handles (if any) off the colander.

2. Watering Pipe. To get water into the reservoir use a 1" PVC pipe, 24" in length. With a 1 3/8" hole saw or another cutting tool, drill or cut off 3 or 4 of the plastic strips in the top or near the top of the colander. The watering pipe will go into this hole down into the reservoir. Cut a notch in the end of the 1" PVC pipe so water will easily flow into the reservoir.

3. Firmly push the colander (upside down, like an upside down bowl, so it forms a dome) into the 5-gallon bucket until it reaches the bottom. If it's a tight squeeze, you can cut small inverted V shaped notches in the colander's rim so it can flex and fit better.

4. Water Overflow / Air Holes. You'll have to create a water overflow/air "tunnel" from inside the colander out through the potting mix and out through a hole on the side of the bucket.
Drill a 3/4" hole in the side of the colander about 1/2" to 1" below the top of the colander (see picture with water dyed blue). Next drill a 3/4" hole on the side of the bucket at a height so the poly pipe will be horizontal. Stick a piece of 1/2" poly irrigation pipe (you could alternatively use a McDonalds or similar drinking straw with smaller holes) through the hole on the bucket's wall and into the colander's dome. There should be about a 1/2" to 1" of air space in the dome above the drainage/air pipe. This will provide a layer of 1/2" to 1" of air for the plant's roots. The pipe will serve as the overflow drain and air path. You want to get air in, and excess water out. You may want to repeat this step with a pipe and hole on the other side of the bucket, as seen in the picture, so you'll have a backup air/water overflow hole in case the primary pipe clogs or fails.

You're done! Just fill with potting mix and plant as described in our videos. As you fill the bucket up with potting mix, firmly pack down the potting mix (like in our planting video) surrounding the colander so water will wick well.

Advantages/Disadvantages/Thoughts: Cheap, about $4.00 to $5.00 US. Only one bucket is used and your time spent drilling holes is reduced by 75%. Like the traditional Global Bucket, it does take a lot of time gathering the materials and setting up, but there should be a time saving over the traditional Global Bucket. This colander system will have a smaller air surface for aeration that the traditional Global Bucket. If there is too much wicking (ie soggy soil) for your plants, you can drill a hole(s) in the side of the bucket below your existing poly pipe hole. This should lower the height of the water level and thus a reduction in the wicking area, but your reservoir will be reduced.

Automatic Watering (like in our irrigation videos): Run the 1/4" tube down the fill tube into the reservoir.

Less is More

The following was designed by Bob Hyland at his wonderful website Inside Urban Green.

Required Tools: All you need is a hot tool to poke holes in the plastic containers (milk jugs, juice bottles, nursery flats, etc) and a hot knife to cut a slot in the bottom side of the bottle(s) to allow free flow of water. There is no need for power tools, PVC tubing and complicated fabrication. For larger images, click on the pictures.

Recycled plastics (food containers, nursery flats) create the soil platform, soil wicks and water reservoir. Five milk containers are used here (about 2 1/2 gallon reservoir capacity). Cut large slots on the bottom side of the containers to allow water entry and poke holes in the top side for aeration and drainage of any excess water. An overflow drain hole (top center) prevents over watering. Recycled water bottles create a fill tube.

Potting mix (NO top soil) packed down between the recycled plastics creates the soil wicking system. The water from the reservoirs will rise by capillary action creating a uniform distribution of water throughout the bucket. Simply pour water down the fill tube until you see some water exit the overflow drain hole (top center).

The tote box lid with the center cut out makes a retainer for a sheet plastic mulch cover (not shown). Recycle the soil mix bag, black side up. This prevents weed growth and water evaporation.

One question about this system is the durability of the milk containers and the inverted nursery trays. How will they stand up through a growing season?

The designer, Mr. Hyland, requests that if you do try this design to please send feedback on your results. Once again, his website is Inside Urban Green.

Here are some other pictures from Mr. Hyland using the same concept:

To make the fill tube, simply cut off the bottoms of plastic water or Coke bottles with a box cutter and stack them for any length fill tube.