Student Learning Continuity Program

11th June, 2020: Session 6

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This is the sixth session of the Student Learning Continuity Program for Years 7-9.

Topic: Growing food for health, self-reliance and food security

Presenters: Adrian Dorovia, John Kela, Vissy Tupou, and Georgina Pita

 Recap of Soil from last week

Today’s Focus is on ‘Soil’. It follows on from our lessons on Photosynthesis and Growing Food. For more information about these, see our previous lessons.

Opening Scenario: 

I would like you to think about two different scenarios: – the same plant was sown on two different soil types.  When the plants grew, one came out with thick green and wide leaves and another with thin narrow pale leaves. In which case would you consider photosynthesis be better?

Answer: the one with green thick and wide leaves will be better. This means the rate of plant growth and the rate of photosynthesis can be affected with the type of soil we select for our food gardens or crops.

Let us continue our study on soil then. Remember that soil is very important for plant growth and photosynthesis.

What is soil?

Soil is the loose upper layer of the Earth’s surface where plants grow. Soil consists of a mix of organic material (decayed plants and animals) and broken bits of rocks and minerals formed through the process known as weathering.

How is soil formed?

Soil is formed over a long period of time by a number of factors. It can take up to 1000 years for just an inch of soil to form. Besides time, other factors that help soil to form include:

• Living organisms – This includes organisms such as plants, fungi, animals, and bacteria.
• Topography – This is the relief or slope of the surface of land where the soil is forming.
• Climate – The overall climate and weather where the soil is forming.
• Parent material – The parent material is the minerals and rocks that are slowly disintegrating (broken down) to form the soil.

Why is soil important?

At first you may think of soil as just dirt. Something you want to get rid of. However, soil plays a very important role in supporting life on Earth.

Here are some important facts about soil:-

• Plants – Many plants need soil to grow. Plants use soil not only for nutrients, but also as a way to anchor themselves into the ground using their roots.
• Atmosphere – Soil impacts our atmosphere releasing gasses such as carbon dioxide into the air.
• Living organisms – Many animals, fungi, and bacteria rely on soil as a place to live.
• Nutrient cycles – Soil plays an important role in cycling nutrients including the carbon and nitrogen cycles (You will learn more about this in Year 10).
• Water – The soil helps to filter and clean our water.

Properties of Soil

Soil is often described using several characteristics including texture, structure, density, temperature, color, consistency, and porosity (absorbency – how slow or hard for water to pass through the soil particles). One of the most important properties of soil is the texture. Texture is a measure of whether the soil is more like sand, silt, or clay. The more like sand a soil is the less water it can hold. On the other hand, the more like clay a soil is, the more water it can hold.

Interesting Facts about Soil Science

• The process by which minerals move down through soil is called leaching.
• In a teaspoon of good soil there will typically be several hundred million bacteria.
• The average acre of good cropland will be home to over 1 million earthworms.

It is possible to over-farm soil and remove so much of its nutrients and organic matter that plants will no longer be able to grow in it.

Activity:

1. Write the chemical equation for photosynthesis and balance the equation. (Form 3 students only).
2. Write down the meaning of the term weathering.
3. Name the four soil types.
4. Write down some important facts about soil that you have just learnt and discuss this with your friend.

Recap – Starting a food garden

1. Select or choose a site or space that is suitable for growing food crops:
   

   Soil that is well drained and rich in organic matter, also where plants can access sunlight and water for healthy growth. If the soil is not fertile, use compost (is a low cost fertilizer that everyone can make from household waste such as vegetable peelings, fruit skins, grass cuttings, leaves, wood ash, manure etc)to improve the soil. Plants need good soil to grow well.

2. Prepare the garden for planting. You need to have the right tools to use:
   

   Clear land of tall grass, bush & weeds Level the ground if there are big holes, then fill in with fertile or good soil Make drains in suitable places so water can run easily when it rains, but does not wash away the good soil. Plan position of the garden beds, add compost or manure to enrich the soil. If it needs protection from animals, build a small fence around it.

3. In caring for the garden, the steps that you need to follow are:
   

   Water the plants daily or every evening. Give your plants enough water to reach the roots and give plenty of water especially in dry weather. Remove weeds as soon as you see them. Put grass cuttings and leaves on top of the garden around the plants to stop soil from drying up and gives food back to the soil. This is called mulching. Plants such as beans & tomatoes need to be tied to a stick. This is called staking. Use insecticides made from natural local materials to prevent pests and insects destroying the garden.