I am digging up a few yards of clay soil for a patio project.
I am hoping to avoid having to throw out this soil and wondering what I can do to it to be useful so i can spread in my garden beds or to grow sod?
Currently my garden beds have triple mix put in but could use more soil to bring the levels up. Is there anything i can do with this soil?
Would be a shame to have to pay to get rid of it if I could use it!
Many regions of Toronto have clay soil so it is a frequent question sent to “Ask a Master Gardener”. You are not alone! And thank you for thinking about how you could augment and use the soil you are removing rather than disposing of it.
This previous post, “How to Fix Clay Soil” on the Toronto Master Gardener website, outlines the differences between clay soil and loamy soil (preferred by gardeners and plants):
“When you have a hand full of regular garden soil you can see how the particles are loosely fit together with spaces for air and water to collect. In clay the particles are a different shape. They are more like flat disks or flakes. When the particles line up the discs of clay fit more snuggly together so there is little or no space for air pockets or space for water to pass through. The more one manipulates the clay the more packed these discs become and what little air and drainage space there was collapse.”
To summarize, the problem with clay soils is the lack of spaces for air and water to pass through and both of these are essential for plant health and for the promotion of beneficial soil micro-organisms.
The horticultural community is in unanimous agreement that adding organic matter to clay soils is the optimal approach. Organic matter not only adds important nutrients, but also works to open up the spaces between clay particles for water, air, and living creatures to use.
This list of types of organic matter, published in a Soil Factsheet from the University of British Columbia, gives you a variety of options you can use:
“well-rotted animal manure, sawdust (do not use cedar), composted garden and kitchen refuse, peat moss, dried seaweed and spent mushroom compost are common organic amendments available to most gardeners.”
Leaving plant leaves, stems, and small branches in your garden over the winter to decompose also adds important organic matter and saves you the job of raking and disposing of this debris in the fall. You might read that sand can be used as well, however, general agreement is that sand can clog whatever pores currently exist in the soil making it even harder to work with.
Your question asks if you can add the clay soil to your already existing garden beds (which contain triple mix) or for growing sod. As these are different uses, I will address them separately.
Triple mix varies in its composition, depending on the manufacturer, but most mixes contain equal portions of sand or peat moss, topsoil, and manure or compost. Adding clay soil to your garden beds is a useful way of repurposing it, providing it is used sparingly, mixed in well and not just added on top of the existing soil. Please also consider adding in extra organic matter before doing this, in order to further break up the clay particles.
In terms of using it for sod, your existing clay soil will need a lot of organic matter to provide a good base for grass. Given that grass is walked on, the soil underneath gets compacted on a regular basis, you might consider augmenting the clay soil with some of the triple mix from your garden beds, or sticking to a higher quality of soil for grass growing. Also take care with watering the sod as clay soils do not absorb water as quickly as other soil types. Again the Soil Factsheet mentioned above gives some specific directions:
“Most lawn sprinklers apply water well in excess of the amount that clay soils can absorb. This results in surface puddling, structure breakdown, reduced air porosity of the soil which will hinder the growth of most seedlings. Add water to a clay soil at less than 0.5 cm/hour to allow absorption.”
I hope these ideas are helpful as you embark on this garden project.