Student Worksheet

Test Your Topsoil - Activity Instructions

Soil and the nutrients it contains are essential for all living things. Have you ever heard of a gardener described as having green thumbs to compliment their wonderful and productive garden? It may be more correct to say they have brown thumbs because it all comes down to what’s in the soil. In this activity you are going outside and getting dirty to find out what the soil is like in your area.

The properties of soil determine the vigour and health of plants. There exists a number of simple soil tests that allow the quality of soil to be determined. The soil quality can then be adjusted to suit the desired plants, be it leafy spinach or a feature plant within a landscaped garden.

Soil moisture and nutrients are two types of soil properties. Being able to investigate soil properties is a neat form of backyard science that anyone can do. What’s more, this is data that can be fed into your family quite literally when the information is used to improve your vegie patch. So it's time to put on a sun hat and break out the gardening gloves as you venture outside.

Safety advice: Conduct a risk assessment of the site. Examples of potential dangers outside: large trees with dead/dying limbs, stinging, biting insects, sunburn and dehydration. Remember, it’s always best to be prepared by having a phone and first aid kit handy.

Part A: Which Ten Soil Properties Are Easily Tested?

Step 1.

With the help of an adult check out a safe location outside such as your backyard or nearby park where you can investigate soil.

Note: Some parks don’t allow digging because they are concerned about damaging landscaping, so try to find a place where you won’t be causing any problems if you dig. And once you’ve finished digging and testing your soil, fill your hole back in and try to leave the area as undisturbed as possible.

Step 2.

Before beginning your soil testing, make sure you have all your equipment, including your notebook to record your observations. You can record soil data using the same headings as each of the steps below.

Soil structure: Make sure the soil is not too wet or dry and dig a hole 25 cm deep. Separate a soil clump with your fingers. Is it cloddy, powdery or granular? Ideally, soil should hold together in small crumbs. This tells us if the soil has decomposing plant and animal material called organic matter. Organic matter allows water and oxygen through the soil which is good for healthy root growth.
Compaction: Plunge the straightened coat hanger wire into the soil. Mark and measure the depth at which it bends. The sooner it bends, the more compact the soil; 30 cm or more of easily penetrated soil is ideal. Compact soil reduces circulation and the movement of important soil animals such as earthworms.
Workability: Use a small hand-held garden fork to try to dig through the soil to turn it over. If it's cloddy the workability is low. This in turn reduces water movement to roots and prevents healthy root growth.
Soil organisms: Dig a hole 30 cm deep and 30 cm, making more nutrients available for healthy plant growth.
Earthworms: Dig a hole 30 cm deep and 30 cm wide. Look for worms. Three are good, however, five are better. An absence of worms means there is not enough organic matter that worms feed upon in the soil. Worms aerate soil and add nutrients.
Organic matter: Look both in the soil you have dug and around the hole/s for recognisable parts of plants. Dark-coloured spongy soil is created by organisms decomposing the organic matter. This organic matter and fast decomposition is another sign of healthy soil.
Plant vigour: Vigour means physical strength and good health. Look for healthy colour and even growth. Plant vigour indicates good soil structure, workable soil and a healthy population of soil organisms.
Root development: Dig gently around a weed you won't miss. Once you’ve loosened the soil around the weed, pull it up. Check for good root development, searching for fine strands with a white, healthy appearance. Brown, mushy roots indicate drainage problems, while stunted roots might indicate disease or pests. Without air, water, soil organisms and crumbly soil to grow in, roots can't do their job.
Water infiltration: Use the can with the bottom removed and push it into the soil until just 8 cm remains above the surface. Fill the can with water, marking the water height and how long it takes for the water to be absorbed into the soil. Repeat this several times until the rate of absorption slows and your times become consistent. Anything slower than 1 to 2 cm per hour is an indication of compacted soil. Good infiltration gets water to the roots, prevents runoff and erosion, and lets air move more easily into soil spaces.
Water availability - OPTIONAL: Wait till a soaking rain has occurred and see how long it takes for the plants to show signs of being in need of watering. If the plants need very frequent watering then there may be a problem with the soil.

Part B: What Matter Is Soil Made From?

Step 1.

Take a sample of soil 10 cm x 10 cm using a trowel and place the soil into a glass jar with a lid.

Step 2.

Add sufficient water to cover the soil by 5 cm. Shake vigorously.

Step 3.

Allow to settle for about 10 minutes.

Step 4.

In your notebook describe the amount and type of organic matter floating on the top.

Step 5.

Can you see layering of sediment on the bottom? Identify the types of sediment, for example, gravel, sand and silt.

Step 6.

In your notebook draw a labelled diagram to show the results.

Taking Action

Become involved as an active gardener. Check out the kids garden projects.

https://www.handyman.net.au/4-kids-garden-projects

Test Your Topsoil (home learning)

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