My new garden experiment

One of the problems with growing vegetables in the dry tropics is that salad vegetables thrive in the winter, but tend to struggle in summer. Thus I have spent a bit of time this year looking into watering systems and have settled on wicking beds as a good line of inquiry. The inventor is an Australian, his webpage is http://waterright.com.au/index.html. While he has some interesting ideas about the politics of food and climate science, he does explain the theories behind his invention well.

Basically, it relies on the fact that soils with good structure carry water upwards. If a reservoir can be created that allows water to be stored under the plants and a continuous system of pores is established, water rises about 25-30 cm. If this is done well, plants can be watered continuously (according to their needs) from below and the surface of the bed remains dry. This means that the system is water efficient and also less susceptible to weed invasion (limited water on the surface lowers weed germination).

While there are lots of interesting ways to structure a wicking container bed, but I prefer the method that uses the soil as the reservoir medium as it lowers both expenses and complexity.

Does it work? Here is a photo of a tomato plant after we were away for a week of heatwave: we got someone from the congregation to top up the water after five days but she didn't have to add much water at all.

 

 The plant at the front is using the simplest form of wicking bed I have made (I use buckets for plants that will spread out broadly, but have a tub for more compact plants), and I made another one today to plant some seeds I received from Ipswich City Uniting Church on Sunday.

What is needed:

A drill with 10mm bit
Tape measure
A tall bucket (preferably 40-50 cm high)
Shadecloth
50 cm piece of hose (wide enough to be poured into with a bucket)

Measure several holes at a consistent height about 30 cm from the top of the bucket, and drill. These limit the height that water can rise up the bucket in rain events and set the height of the reservoir. This stops the soil from getting waterlogged and allows air into the soil.

Line the bucket with the shadecloth to cover the holes. This stops soil leaking our when the reservoir is filled and prevents mosquitoes and other pests from entering through them.

Make up a mix of 50% potting mix and 50% compost - I also added a little horse manure as the species I am planting are rather vigorous. This pot uses about half a bag of each.

Place a little of the soil on the base of the pot and insert the watering pipe.

Fill the rest of the pot with soil.

Fill the reservoir with water (fill until water flows through the holes), use another pot to provide a cover for the watering hose and then you're ready to plant.

These are a simple bed but it is important to remember they are closed systems - it is important to let them dry out occasionally and also it is good for them to get a thorough drenching occasionally. It is also necessary to be careful about additions of fertilisers, the lack of runoff means that nutrients can build up to harmful levels. I am planning to double up our tub bed by using a worm farm in it to process compost into soil that can be used to fill up the bucket beds.