Submitted By: Egan Davis, Principal Instructor (UBC Botanical Garden)
To learn more about soil quality, you need to use your senses by looking, touching and smelling it. This summary overviews some of the simple ways you can test the soil quality in your home garden. To read the full article, see here.
Assessing Soil Quality – Look, Feel and Smell
- Make sure you have an adequate soil sample – the larger the area, the more collections you should take.
- A balanced blend of fine and coarse mineral materials with a good percentage of organic material is ideal.
- Are there healthy plants growing in the soil already? “If it ain’t broke, don’t fix it”.
- Is there mulch or a groundcover of plants on the surface of the soil? Soil cover provides habitat and nutrient-recycling materials, limits weed growth and reduces root competition between plants.
- What colour is the soil? If the soil is dark in colour, it is likely rich in organic material. Red and orange colours may indicate highly aerated, oxygen-rich soils. Soils that are grey (or bluish-grey) may have low oxygen levels.
- Is the soil well-structured? Most plants thrive in porous soil.
- The Soil Ball Test – Moisten a ball of soil and roll it gently between the palms of both hands. Is it easy to roll the ball without it falling apart? Now gently toss the ball up and down in your hand, letting it fall against your open palm. Does it break apart on the first toss? If the ball crumbles easily, the soil is quite sandy. If the ball sticks together well, the soil has fine particles such as slit, clay or organic humus.
- The Worm Test – Try to roll a moistened sample in between your palms into a worm shape. If you can roll the soil into a worm, this indicates the presence of fine particles.
- The Grittiness Test – Rub a moistened sample between your thumb and index finger. A gritty feeling is an indication of sand particles. A slick feeling is an indication of finer particles of silt, and a greasy feeling indicates the presence of clay. If you feel both textures, your soil might have a mix of particle sizes.
- The Ribbon Test – Try to push out a ribbon of soil over your index finger with your thumb. It is impossible to form any ribbon at all with sandy soils. If the soil has fine particles like silt, you can start a ribbon but it breaks as soon as it protrudes past your finger. With a clay soil, you can make a ribbon that holds together for a significant length as you push out the material past your finger.
- An organic soil will smell like mushrooms. You can often smell the rusty smell of iron in mineral soils. Acidic soils will smell sour. A sulfuric, rotten egg smell indicates a very poorly-aerated soil.
Work with What You Have
If you understand the type of soils you are working with, it is easier to choose plants that suit the site. Where you think you have a challenge, you might actually have an opportunity!
Working with Compacted Soil
Soil can be damaged very quickly if it is walked on, especially when it is wet. Repetitive digging, cultivating and weeding also damage structure, which can compact soils. A helpful way to decompress compacted soil is to it simply stick a garden fork into the depth of the prongs and rock the tool back and forth, fracturing and lifting the soil. Follow up by mulching the soil with leaves or compost – focus on developing a rich surface layer that somewhat mimics the complex surface layer of debris in a forest.
It is important to understand soil quality when making decisions in the garden. Soil needs to breathe, water needs to move through it, and it has to be a healthy environment for a complex food web of insects, worms and micro-organisms. Organic matter improves all of these qualities and it can be added to soil as a mulch. Try to emulate natural systems in your garden – have fun and get your hands dirty!