The soil used in container gardening - and particularly in the self-watering GrowBarrels - is very special. GrowBarrels, because they are always moist, must contain a soil that can retain water, but that also has components which will keep the soil from compacting and losing oxygen (because plants need it too). The right amount of nutrients are found in the soil, and a good, fairly neutral pH (not too acidic, not too basic) should be achieved. As always, sustainability is a main consideration for the Como Green Village. Here are some things to think about as you design your own soil in future years!
GrowBarrel 2011: The Soil Choice
Outback Nursery and Landscaping. We were really impressed with their Outback Nursery Mix because it contained many ingredients perfectly suited to GrowBarrels. The soil was:
Sphagnum Peat Moss: The Controversy
Canadian Peat Bog
Spagnum Peat Moss is....complicated. For our purposes, it is really the best material currently available to retain air and water in the GrowBarrels. However, there is a great deal of controversy regarding whether it is really sustainable because it is harvested from peat bogs and is a product of carbon, similar to fossil fuels but not as ancient; it is questionable how quickly the bogs can regenerate after being harvested. We decided to use it for this project despite the ongoing debate for several reasons:
As always, though, SECIA's Green Village is on the lookout for more sustainable options. In the mean time, here are some resources to help you determine whether you think sphagnum peat moss is sustainable or not. Click on the title to see the website or Google Document. The documents can also be downloaded for printing below in the Attachments section.
Canadian Sphagnum Peat Moss Association
Review regulations, research, and industry practices
Of specific interest are their report on the peat moss
industry and the Code of Practice.
Sphagnum: A Keystone Genus in Habitat Restoration
A research article exploring the ecological role of peat bogs.
Sphagnum farming: local agricultural production of a horticultural peat substitute
A research article exploring the possibility of
sustainably farming peat
Greenhouse Gas Emissions
An analysis of GHG emissions from peat harvesting
Resources to Help You Choose Your Soil
******The Main Soil Considerations****
Air and Water!
Soil isn't the particles and matter in it - it's also the air between its components. Plants need this air and space to make a sufficient root system and grow successfully. Therefore, in container gardening it is especially important to design soil so that it does not compact, maintaining the space for the air and water. Here is a suggested recipe and some tips that Ed Smith (author of Incredible Begetables from Self-Watering Containers) provides for designing your own soil:
Tips for Designing your own Soil: