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

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

Presenters: Georgina Pita and Rose Paia

Soil

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.

 

Selecting Plant Materials

Now that we know how important the soil is, we also need to think about selecting plant materials.

What do we mean by planting materials?

Planting materials refer to the part of plant that will go into the soil and grow into food crop. Seeds, cuttings and suckers are all examples of planting materials.

Here are guidelines that will help you select suitable planting materials so that your crops grow successfully. Ensure the planting material…

• Comes from plants that grow well in specific soil and climatic condition of your site
• Is healthy
• Is resistant to pests and diseases
• Matures early
• Produces high yield, or large amount of food crop

Sowing seeds

Direct sowing

Some food crops are sown or planted directly as cuttings (refers to part of plant that will be planted to make new plant). Another way to plant food crops is to sow seeds (from some crops like beans, corns and peanuts, have seeds that are sown straight into planting bed where they will germinate and grow. This is called direct sowing.

Direct sowing is best used for food crops that meet the following requirements/conditions;

• Have big seeds
• Germinate easily
• Grow and establish easily
• Would be difficult to transplant

The plots or planting beds, where food crops will grow must be prepared before the seeds are sown. The seeds must be planted in holes. When the seeds are sown directly, ensure the seeds are planted at the correct depth, and with enough space between the seeds. Ensure 2 seeds are sown in each planting hole.

Starting a seedling nursery

Not all types of food crops can be sown directly into the site where they will grow. Some food crops must be raised in a separate area as seedlings, then transplanted to the field or area where they will grow and develop. A place where we sow and raise seedlings is called a nursery.

When choosing a site for your seedling nursery, ensure it is;

• Near a source of water
• A short distance from garden site
• Free from pests
• Close to the house
• Flat area
• Well drained soil

Recap: we have just learned about two ways of sowing seeds: direct sowing, and nursery. In direct sowing, seedlings, such as beans, corns, water melons, and peanuts, are planted directly into the soil. In seedling nursery, crops are raised in nursery beds before they are transplanted into the main garden beds.

 

Home take away activity

Copy the following questions into your exercise book. Then answer the questions.

1. List important factors that must be considered when choosing a site for growing food crops.
2. Why do you think a site is suitable or not suitable for growing food crops?
3. If a site is not suitable, are there ways you can still grow food crops in the area?
4. Why do you think some food crops are grown through direct sowing and some are not?

 

English Activity:

Last week, you were asked to identify or select a local food, eaten and grown in your village or community and write a set of instructions on how to grow and care for that particular vegetable or root crop (eg. beans, chinese cabbage).

For our sample, we chose beans.

Growing Beans:

1. Firstly, prepare planting beds for direct sowing.
2. Then dig a hole and make sure it is of correct depth.
3. Now place two seeds inside the planting hole.
4. Finally, ensure there is enough space between the seeds.

You can see that we have written 4 clear instructions on how to grow beans. Looking at these instructions, identify the parts of the instructions that have been put together:

• verbs – action words – the actions you take to grow the beans
• nouns or noun groups – the things you need to have to grow the beans
• words such as firstly, secondly, etc. to describe when to do each step (these are a type of adverb)

Read your own instructions and check that you have these kinds of words.

Imperative commands are used in these instructions. They can also be used in recipes and other explanations of how to do a range of processes.