Grade 7 Agriculture & Nutrition Study Notes

Causes of Soil Pollution

Cause 1: Wastewater

Wastewater is dirty water that has already been used — for example, water from washing clothes, mopping floors, or washing dishes. It contains soaps, detergents, and other chemicals.

Common household activities that produce wastewater include washing clothes, mopping floors, washing dishes, and bathing — making this one of the most frequent sources of soil pollution right at home.

When wastewater is poured directly onto soil, those chemicals soak into the ground. Over time they build up and damage the soil, making it harder for plants to grow.

Conservation of Resources

Conservation of resources means using natural resources wisely to avoid wastage, destruction, or depletion. Conservation ensures there are enough resources for future use.

What this strand covers

• Controlling soil pollution
• Constructing water retention structures
• Conserving food nutrients
• Growing trees

This first lesson begins with Sub-Strand 1.1 — understanding what soil pollution is and what causes it.

What is Pollution?

Pollution is when harmful substances are introduced into the environment, making it dirty or unsafe.

The environment includes the air, water, and soil around us. Any of these can be polluted when harmful substances enter them. In this sub-strand, we focus on soil.

Cause 2: Excessive Use of Artificial Fertilisers

Artificial fertilisers are manufactured chemical products that farmers add to soil to help crops grow. They come in bags as granules or powder.

When used in the correct amounts, they help crops. When used excessively — far more than needed — the extra chemicals build up in the soil. This build-up harms the soil and can make it toxic to plants over time.

What is Soil Pollution?

Soil pollution happens when harmful substances contaminate the soil, making it unhealthy for plants, animals, and humans.

Healthy soil is dark brown, loose, and crumbly. It contains air spaces, moisture, and tiny living organisms that help plants grow. When soil is polluted, harmful substances mix into it — the soil may become pale, compacted, or stop supporting plant growth.

When soil is polluted, crops grown in it produce less food and may be unsafe to eat. People, animals, and the organisms that keep soil healthy are all harmed — which is why preventing soil pollution matters.

Cause 3: Improper Use of Agricultural Chemicals

Agricultural chemicals are products used on farms to control pests, diseases, and weeds. They include pesticides (which kill insects and other pests) and herbicides (which kill weeds).

These chemicals pollute the soil when used in the wrong amounts, or when their containers are left lying on the ground after use. Chemical residues seep from discarded containers into the surrounding soil.

The Four Causes of Soil Pollution

There are four main causes of soil pollution you need to know:

• Wastewater — dirty water from household activities
• Excessive use of artificial fertilisers — too much manufactured fertiliser applied to crops
• Improper use of agricultural chemicals — pesticides and herbicides used wrongly or disposed of carelessly
• Plastic waste — plastic bags, bottles, and containers discarded on or in the soil

When you see soapy water poured on soil, fertiliser applied carelessly, pesticide containers left in a field, or plastic scattered in a garden — you are looking at one of these four causes.

Cause 4: Plastic Waste

Plastic waste refers to discarded plastic objects — including plastic bags, bottles, containers, and packaging. These are common in homes, markets, and gardens.

Unlike leaves or food scraps, plastic does not break down easily in the soil. It can stay in the ground for many years. While there, it blocks water and air from moving through the soil to plant roots. It can also release harmful chemicals into the surrounding soil.

Summary: The Four Causes and How They Harm the Soil

Soil pollution has real consequences. Crops grown in polluted soil grow poorly and may be unsafe to eat. Animals that graze on polluted land can fall ill. Humans who eat food from polluted soil are also at risk. Recognising these effects is what makes it worth acting on.

Controlling Soil Pollution

Controlling soil pollution means stopping harmful substances from getting into the soil. It also involves improving soil that has already been polluted.

There are different ways in which soil pollution can be controlled:

• Disposing of wastewater safely
• Reusing plastic containers
• Taking plastic waste to a recycling centre
• Practising safe farming methods
• Creating awareness messages

Of these, the wastewater rule is the simplest to remember: soapy or dirty water must always go into a toilet or latrine — never onto garden soil.

Responsibility means not waiting for someone else to act. Every time you carry wastewater to the latrine, pick up a plastic container instead of leaving it on the ground, or remind a classmate to dispose of waste correctly — you are controlling soil pollution.

Disposing of Wastewater to Control Soil Pollution

Why Soapy Water is Harmful to the Soil

Soapy water contains chemicals that are harmful to the soil and to plants. These chemicals come from the soaps and detergents used during washing. Even a small amount poured repeatedly onto the same patch of soil causes damage over time.

This is why how you get rid of wastewater matters — not just the amount, but where it goes.

Disposing of Plastic Waste to Control Soil Pollution

Method 1: Reusing Plastic Containers

One way to deal with plastic waste is to reuse it. Instead of throwing a plastic bottle or container away — where it could end up in the soil — it is given a new purpose as a plant pot for growing crops.

The course book shows learners who have collected plastic containers and are using them to grow crops. This keeps plastic out of the soil and creates more growing space.

How to Reuse a Plastic Bottle as a Plant Pot

1. Collect a clean plastic bottle or container.
2. Make small drainage holes in the base.
3. Fill the container with soil.
4. Plant your seedling inside and water it.

The Correct Way to Dispose of Wastewater

The course book uses the example of Kerubo, who has just finished washing her clothes and needs to dispose of the soapy water responsibly.

The correct rule is: dispose of soapy water in a toilet or a latrine.

A toilet or latrine connects to a waste system that keeps the chemicals away from garden soil and from water that people and animals use.

Method 2: Taking Plastic Waste to a Recycling Centre

Plastic that cannot be reused should be taken to a recycling centre — not burned, not buried, and not left on open ground.

At a recycling centre, plastic is collected, sorted, and processed into new materials. This keeps it permanently out of the soil.

What the Control Practices Look Like

The course book shows four practices side by side. Here is what each one involves:

How to Dispose of Wastewater — Step by Step

The course book asks learners to practise this at school. Here are the steps:

1. Collect the wastewater in a bucket or basin.
2. Put on gloves and gumboots before carrying it.
3. Carry the bucket to the toilet or latrine.
4. Pour the wastewater in carefully.
5. Rinse the bucket with a small amount of clean water and dispose of that rinse water the same way.
6. Wash your hands with soap and clean water afterwards.

Why Proper Plastic Disposal Matters

Proper disposal of plastic waste matters because plastic that ends up in soil stays there for many years. It prevents water and air from reaching plant roots, reducing crop yields. When animals eat or drink near polluted land, the chemicals released by plastic can harm them. Humans who eat crops from such soil are also affected.

Reusing and recycling plastic breaks this chain before the harm begins.

Remember: Controlling soil pollution protects the health of plants, animals, and humans. Always wear protective gear when carrying out soil pollution control practices.

Protective Gear

Always wear protective gear when handling wastewater or chemical containers. Protective gear protects you from the harmful substances and organisms in wastewater that could cause illness.

• Rubber gloves — protect hands from chemicals and germs
• Gumboots — protect feet and lower legs

Making this a habit — at school and at home — is what it means to demonstrate responsibility in preventing soil pollution.

Safe Farming Methods to Conserve the Soil

Safe farming methods are ways of farming that protect the soil from pollution and damage. They involve being careful about what goes into the soil and how farm inputs are handled and disposed of.

Safe farming methods are important because every harmful substance that enters the soil through farming affects not just that one farm — it can move through water flow to neighbouring land, harm the crops and animals of other families, and eventually reach the food and water that people in the community depend on.

Safe Farming Methods — Matched to Each Cause

Each safe farming method directly addresses one of the causes of soil pollution already studied:

Adopting safe farming methods means making these practices your own — not as a once-off classroom exercise, but as the normal way you farm at home and at school. Start with what is within your control: apply fertiliser correctly, never leave chemical containers in the field, and manage plastic waste properly.

Creating Awareness Messages Against Soil Pollution

An awareness message is a short, clear communication that tells people about a problem and what they should do about it. Awareness messages help inform and remind the community to act responsibly.

For soil pollution, awareness messages help people understand what causes soil pollution and what they can do to stop it.

Each learner who makes and shares a poster, or talks to a neighbour about wastewater disposal, becomes part of the change. One person informing five people — who each inform five more — spreads the message further than any single teacher or authority could. That is why your role matters.

A Soil Conservation Poster

The course book shows a poster made by a Grade 7 learner carrying the message: "Stop soil pollution — Save Earth."

A poster is one of the most effective ways to spread an awareness message. It uses bold text and simple visuals so that any reader can understand the message at a glance.

Topics for Awareness Messages

The course book identifies three specific topics that awareness messages should address:

How to Make a Poster

What makes a message effective is that it is short and direct, names one specific action, and uses plain language anyone can understand. A message that is too long or too general will be ignored.

Include these three things in your poster:

1. A clear, bold headline — the main message, readable from a distance
2. A short message — one or two sentences on the problem or the action needed
3. A simple image or symbol — to help people understand even without reading all the words

Share the completed poster with classmates — spreading the message is the whole point of making it.

Key Points — Sub-Strand 1.1: Controlling Soil Pollution

• Pollution is the introduction of harmful substances into the environment, making it dirty or unsafe.
• Soil pollution happens when harmful substances contaminate the soil, making it unhealthy for plants, animals, and humans.
• The four causes of soil pollution are: wastewater, excessive use of artificial fertilisers, improper use of agricultural chemicals, and plastic waste.
• Wastewater from household activities contains chemicals that damage soil when poured onto it — it must go into a toilet or latrine.
• Excessive fertilisers cause chemical build-up in the soil when used in amounts greater than recommended.
• Agricultural chemicals pollute the soil when used incorrectly or when containers are left in the field after use.
• Plastic waste does not break down easily — it blocks water and air in the soil and may release chemicals for many years.
• Controlling soil pollution means stopping harmful substances from entering the soil and improving already polluted soil.
• Control practices include: safe wastewater disposal, reusing plastic containers to grow crops, taking plastic to a recycling centre, and safe farming methods.
• Always wear protective gear — gloves and gumboots — when handling wastewater or chemical containers.
• Safe farming methods directly match each cause: correct fertiliser amounts, proper container disposal, managed plastic waste, and wastewater directed to a latrine.
• Awareness messages — such as posters — communicate what people should and should not do. They work best when they are short, direct, and name a specific action.
• Every learner has a role to play — at school, at home, and in the community.

Use of Surface Run-off in Gardening

Surface run-off is water that flows over the ground after it rains. Instead of soaking into the soil, it flows along the surface and is often wasted. Run-off water can come from rain, springs, and streams.

Water retention structures hold this run-off water and allow the soil to absorb it slowly. This keeps the soil moist for longer and supports the growth of plants in gardening.

Without water retention structures, surface run-off flows away and is lost — the garden misses out on water that could have helped crops grow.