Soil, Compost and Watering

What’s under a Lethbridge yard

The prairie around Lethbridge grew some of the best natural soil in the country. Alberta Agriculture describes the Dark Brown Chernozemic soils of this part of the province as having a dark brown surface layer about 12 to 15 cm thick, with roughly 4 to 6 per cent organic matter. To the southeast, toward the drier country, the soil becomes Brown Chernozemic, with a thinner surface layer and less organic matter.

Your yard may not have much of that, though. When a neighbourhood is built, the topsoil is often scraped off, the ground is levelled and packed by heavy equipment, and a thin layer of soil goes back on top before the sod. What’s left in many city yards is:

Three soil tests you can do at home

1. The squeeze test (is it ready to work?)

Take a handful of moist soil and squeeze it hard in your fist, then open your hand.

• It falls apart right away: sandy soil. Drains fast, dries fast.
• It holds its shape, then crumbles when you poke it: good loam, and ready to dig.
• It stays a sticky, shiny lump you could shape like modelling clay: clay, and too wet to work. Wait a few days and try again.

2. The jar test (what’s it made of?)

1. Collect soil from about 15 cm down, pick out stones and roots, and fill a clear straight-sided jar about one-third full.
2. Add water until the jar is nearly full, plus a teaspoon of dish detergent to help the particles separate.
3. Shake hard for a few minutes, then set it somewhere it won’t be bumped.
4. Mark the layers. Sand settles in about a minute. Silt settles over the next couple of hours. Clay can take a day or more, and the water may stay cloudy for days if you have a lot of it.
5. Compare the thickness of each layer. Roughly equal sand, silt and a smaller amount of clay is loam. A thick top layer of clay, and water that won’t clear, tells you why your yard puddles.

3. The drainage test (where does the water go?)

1. Dig a hole about 30 cm deep and 30 cm wide where you want to plant.
2. Fill it with water and let it drain completely. This wets the surrounding soil.
3. Fill it again and measure how far the water drops in an hour.

A drop of 2.5 to 5 cm an hour is good drainage for most plants. Much slower means compacted clay or a hard layer below; plan on raised beds or plants that tolerate wet feet. Much faster means sandy soil that will need more frequent watering and plenty of compost to hold moisture.

Fixing clay: compost, not sand

It sounds logical: clay is too fine, so mix in something coarse. But the University of Saskatchewan’s gardening program warns against it. Mixing small amounts of sand into clay can make something close to concrete, and you’d need to add roughly as much sand as there is soil to change the texture. The real problem with clay isn’t the size of its particles. It’s that the particles are packed together with no structure: no crumbs, cracks and pores for air, water and roots.

Structure comes from organic matter and the living things that feed on it. Worms, fungi and soil microbes glue clay particles into crumbs. Feed them, and they’ll fix your soil for you.

• Add compost every year. A layer of 3 to 5 cm on vegetable beds each spring or fall is a good habit. Spread it on top; the worms will take it down.
• Dig less. Rototilling breaks up crumbs and, over the years, tends to compact clay further, especially if it’s done when the soil is wet. Once a bed is established, loosen it with a fork instead.
• Never work wet clay. Do the squeeze test first. Digging or walking on wet clay squashes out the air and can ruin its structure for the season.
• Stay off the beds. Make beds narrow enough to reach the middle from a path, about 1 to 1.2 m wide, so you never have to step in them.
• Mulch. A permanent layer of wood chips on paths and around shrubs feeds the soil from above, year after year.

Raised beds

If your soil is poor fill, very heavy clay, or drains badly, a raised bed lets you start fresh on top of it.

• Height: 20 to 30 cm is enough for most vegetables. Taller beds are easier on the back and knees.
• Fill: a mix of good topsoil and compost, roughly two parts soil to one part compost. Loosen the ground underneath with a fork first so roots can keep going down.
• Watch the drying: raised beds warm up earlier in spring, which is a real advantage here. But in our wind and sun they also dry out faster than in-ground beds, so mulch them and check moisture more often.
• Materials: untreated wood, stone, brick or metal all work. Avoid old railway ties and treated wood of unknown age around food crops.

Mulch

If you only change one thing about your Lethbridge garden, mulch it. A layer of mulch keeps soil moist and cool, stops wind from blowing the topsoil away, smothers weed seedlings, and keeps clay from crusting after rain. Organic mulches also feed the soil as they break down.

Composting in a dry, windy climate

Composting is the same everywhere: mix “greens” (kitchen scraps, fresh plant trimmings, coffee grounds) with “browns” (dry leaves, straw, shredded cardboard), keep it damp and give it air. But in Lethbridge, the most common reason a pile doesn’t work is simple: it’s too dry. Wind and sun pull the moisture out, and a dry pile just sits there for years.

1. Pick a sheltered, partly shaded spot out of the worst of the west wind, on bare soil so worms can move in.
2. Use a closed bin or cover the pile. A lid, an old tarp or a piece of carpet holds moisture and keeps the pile from blowing around.
3. Aim for about two parts browns to one part greens by volume. Save bags of fall leaves to mix with summer’s kitchen scraps.
4. Keep it as damp as a wrung-out sponge. In summer, that may mean adding water every time you add material. Wet the browns as you add them.
5. Turn it every few weeks if you want faster compost. If you don’t, it will still get there, just more slowly.
6. Keep out meat, bones, dairy and oily food (they draw animals), diseased plants, and weeds that have gone to seed. The City’s green cart takes those things instead.

Watering: deep, early, less often

Roots grow where the water is. Water lightly every day and you train plants to keep their roots in the top few centimetres, which dry out by mid-afternoon on a hot, windy day. Water deeply and less often, and roots follow the moisture down to where the soil stays cool and damp.

• Treat 2.5 cm a week as a starting point, not a rule. In a hot, windy week in July, many gardens need more. In a cool, showery June, they may need none.
• Measure it. Set a straight-sided tuna can or a rain gauge under the sprinkler and time how long it takes to collect 2.5 cm. You may be surprised.
• Check, don’t guess. Push a finger or a trowel into the soil. If it’s dry 5 cm down, it’s time to water.
• Water in the morning. Mornings here are usually calmer and cooler, so more water reaches the roots, and leaves dry off during the day, which helps prevent disease.
• Water the soil, not the leaves, wherever you can.
• On clay, water slowly or in two rounds. Clay soaks water up slowly, so fast watering runs off. Water until it starts to puddle, wait half an hour, then water again.
• Pots and hanging baskets are different. In July they can need water every day, sometimes twice.

Catching rain and snowmelt

In a city that gets only about 375 mm of precipitation a year, every bit you catch counts. And plants prefer rainwater: it’s soft, at air temperature, and free of the chlorine in tap water.

• Rain barrels: one barrel on a downspout fills surprisingly fast. A summer thunderstorm on a typical roof can fill it in minutes. The City of Lethbridge has offered rebates on rain barrels through its Environmental Incentive Program in recent years, and posts a guide to building your own. Check lethbridge.ca for what’s on offer this year.
• Use it up between storms, so the barrel has room for the next one. A full barrel catches nothing.
• Cover it with a screen to keep out mosquitoes, leaves and curious children and pets.
• Snowmelt: shovel clean snow onto garden beds and around shrubs and trees rather than onto the driveway or street. It insulates plants through cold snaps and soaks in when it melts. Avoid snow from the street or sidewalk, which carries salt and grit.
• Empty and store barrels before freeze-up in October, or they can crack.

Drip lines and soaker hoses

Sprinklers throw water into the air, where Lethbridge wind can carry a good share of it into the neighbour’s yard or the street. Drip lines and soaker hoses put water right at the soil, slowly, where clay can actually soak it up.

Sources

• Alberta Agriculture, Agricultural Land Resource Atlas of Alberta: Soil Groups of Alberta (Dark Brown and Brown Chernozemic soils).
• University of Saskatchewan, Gardening at USask, “Adding sand to clay soils is not recommended”.
• City of Lethbridge, Water conservation page and news release on curbside organics and compost giveaways (2026).
• Lethbridge Herald, “City offers rebates for toilets, rain barrels”, April 2025 (Environmental Incentive Program).
• University of Alberta, Department of Biological Sciences, Alberta earthworm research project, “How do earthworms spread?”
• Environment and Climate Change Canada, Canadian Climate Normals 1991–2020, Lethbridge Airport (annual precipitation).