If you’ve ever grown a garden, you’ll understand that plants need healthy soil to grow. But just what is soil?
Soil is a living ecosystem made up of sand, silt and clay particles, as well as minerals, organic matter and pockets of moisture and air. Soil organic matter consists of both decaying plant material and living organisms that make their home in the soil. This includes small mammals and insects, as well as tiny microorganisms that turn decaying plant material into food for plants.
Did you know that soil is the most diverse habitat on earth? It is teeming with life. One small handful of healthy soil contains more living organisms than the entire population of humans on Earth!
Why is healthy soil so important?
Healthy soil supports plants, animals and human life. Farmers rely on healthy soil to be able to grow food for Canadians and to export to consumers in other countries around the world. Soil is the most critical factor in our ability to grow nutritious plentiful food. It also plays a major role in helping reduce greenhouse gases and improve water quality.
It all comes down to carbon, which is part of all organic (living) organisms and one of the key components of healthy soil.
All plants use the sun’s energy to break down carbon dioxide (CO2) and water (H2O) to build the molecules they need for growth. This process is called photosynthesis and it’s what makes life on earth possible. When carbon compounds are returned to the soil through photosynthesis, it increases the amount of organic matter in the soil, thereby improving soil health. This process also contributes to a healthier environment by removing greenhouse gases (GHGs) – like CO2 – from the air.
In 2019, soil used for agriculture activities in Canada removed approximately 4.2 million tonnes of CO2 from the atmosphere.
Soil organic matter also is an indication of the amount of carbon in the soil. It improves nearly all functions of soil by:
- Regulating water supply. It helps to filter water during floods and stores water during drought.
- Holding soil particles together and creating soil pores (spaces between solid particles). These pores can be filled with water or air which allows for the movement of nutrients. Pores give plants a place to grow their roots which means better plant growth.
- Containing essential nutrients like nitrogen, phosphorus and sulphur necessary for plant growth.
- Providing the energy that soil microorganisms require to be able to break down plant matter into nutrients that the plants can use.
Do all farms have the same soil?
The answer is no. No two farms in Canada have the same soil makeup. Soil types vary from region to region in Canada. For example, soil on a Prince Edward Island farm is different from soil on an Ontario farm. Soil can even vary within a single field.
All soil is made up of parallel horizontal layers called horizons. The first horizon layer is about 10-25 cm deep and is called topsoil. It is this layer that contains the organic matter, nutrients and water that are essential for sustaining life.
Maintaining soil health
Regardless of type of soil, farmers across the country recognize the importance of keeping soil healthy. Some of the farming practices that improve soil health include:
- Increasing the soil’s organic matter by leaving crop residues (the remains of last year’s crop) in the field. Some farmers also add organic matter to fields, like manure from farm animals or compost.
- Minimizing soil disturbance by practicing conservation tillage, a seeding technique where soil isn’t worked before planting. Roots and organic matter from the previous crop hold the soil in place, preventing soil erosion and enhancing soil’s ability to hold water.
- Adding other plants to the ecosystem can increase organic matter and reduce soil erosion. This can be done by planting trees or shrubs around fields or growing perennial plants like forages, which are crops like alfalfa used for animal feed.
- Incorporating cover crops, which are crops that are inter-seeded with the main crop but remain unharvested. Cover crops protect the soil by providing erosion control, improving soil water storage, increasing soil nutrients and supplementing organic matter.
We’ve come a long way when it comes to understanding soil health and the farming practices that contribute to it. It takes a sustained effort to ensure that soil remains healthy to be able to produce food for an ever-growing world population, and in ways that continue to support the health of our water and the environment.