Fertilizer and Manure Application – SS1 Horticulture and Crop Production Lesson Note (Second Term)

Fertilisers and manures are materials added to the soil to supply the nutrients plants need to grow.

Behavioural objectives

By the end of the lesson, students should be able to:

1. state the functions of nitrogen, phosphorus and potassium in plants;
2. name four types of organic manure and give one use of each;
3. name common inorganic fertilisers and state their advantages and disadvantages;
4. describe the four methods of fertiliser application;
5. state the rules for applying fertiliser safely.

What are fertilisers and manures?

Manures are organic materials from plants and animals, while fertilisers are inorganic materials made in factories.

• Nutrient: a chemical element that a plant needs in order to grow and stay healthy.
• Manure: organic material from plant or animal waste, such as poultry droppings and compost.
• Fertiliser: a factory-made chemical product that supplies plant nutrients, such as NPK and urea.
• NPK: the three main nutrients, nitrogen (N), phosphorus (P) and potassium (K).

Why do we feed plants?

We feed plants because crops remove nutrients from the soil, and these nutrients must be replaced.

• Horticultural crops are grown intensively, so they use up soil nutrients quickly.
• Rain washes some nutrients out of the soil (leaching).
• Soil that lacks nutrients gives a poor harvest.
• Fertilisers and manures put the nutrients back.

What are the three main plant nutrients (NPK)?

The three main plant nutrients are nitrogen, phosphorus and potassium.

What is organic manure?

Organic manure is a plant nutrient source made from the remains or waste of living things, plants and animals.

What are the types of organic manure?

Four common types of organic manure are poultry droppings, cow dung, compost and green manure.

• Poultry droppings: very common in Nigeria and rich in nutrients, especially nitrogen.
• Cow dung: improves the soil’s ability to hold water.
• Compost: made from kitchen waste, dried leaves and grass that have rotted into dark, rich soil.
• Green manure: a crop such as beans, ploughed into the soil while still green to rot and feed the soil.

Notes on poultry droppings

• Fresh droppings are very strong.
• Allow them to cool and decompose before use.
• If used fresh, they can burn the plants.

What are the advantages of organic manure?

• Long effect: it releases nutrients slowly and keeps feeding the soil for more than one season.
• Soil structure: it makes the soil soft and crumbly.
• Water holding: it helps the soil keep water.
• Low cost: it is cheap or free if you keep animals or have plant waste.
• Safety: it has a low risk of burning crops.

What are the disadvantages of organic manure?

• Slow action: it does not cure a hungry plant quickly.
• Bulky: large amounts are needed, so it is hard to carry and spread.
• Variable content: the amount of nutrients is not the same in every batch.

What is inorganic fertiliser?

Inorganic fertiliser is a chemical plant food made in factories, often called chemical fertiliser.

What are the common inorganic fertilisers?

Three common inorganic fertilisers are NPK 15-15-15, urea and sulphate of ammonia.

• NPK 15-15-15: the most popular in Nigeria, with equal amounts of nitrogen, phosphorus and potassium.
• Urea: white granules that are very high in nitrogen and make leaves greener.
• Sulphate of ammonia: supplies nitrogen and sulphur, and tends to make the soil more acidic.

What are the advantages of inorganic fertiliser?

• Fast action: it works quickly on plants showing hunger signs.
• Easy to carry: it is sold in bags and needs little space.
• Known content: the bag states the amount of nutrients.

What are the disadvantages of inorganic fertiliser?

• Easily washed away: heavy rain carries it out of the soil.
• Risk of burning: too much can scorch and kill crops.
• No soil improvement: it does not improve soil structure as manure does.
• Cost: it must be bought.

What is the difference between organic manure and inorganic fertiliser?

Organic manure comes from plant and animal matter, while inorganic fertiliser is made in factories from chemicals.

What are the methods of fertiliser application?

There are four methods of fertiliser application: broadcasting, ring application, row (side) dressing and foliar application.

1. What is broadcasting?

Broadcasting is scattering fertiliser evenly over the whole field by hand.

• Best for: grains or crops planted very close together.

2. What is ring application?

Ring application is placing fertiliser in a circular trench around a plant.

1. Dig a small circular trench a few centimetres away from the stem.
2. Put the fertiliser in the trench.
3. Cover it with soil.

• Best for: tree crops such as orange and cocoa, and single plants such as pepper.

3. What is row or side dressing?

Row or side dressing is applying fertiliser in a straight line along the rows of a crop.

• Best for: crops planted in clear lines, such as maize and okra.

4. What is foliar application?

Foliar application is spraying fertiliser dissolved in water onto the leaves.

• Best for: giving a quick boost to flowers and vegetables.

What are the rules for applying fertiliser safely?

Four rules for safe fertiliser application are keep it off the stem, use water, apply little and often, and cover it with soil.

1. Keep it off the stem: fertiliser is salty and burns the plant. Only foliar spraying is applied to leaves.
2. Use water: fertiliser must dissolve before roots can take it up. Apply to moist soil or water the plants straight after.
3. Little and often: two small doses are better than one large dose.
4. Cover it with soil: this reduces loss by rain runoff and, for nitrogen fertilisers such as urea, loss into the air as gas.

Evaluation

1. State the function of nitrogen, phosphorus and potassium in plants.
2. Why must poultry droppings be allowed to decompose before use?
3. Give two advantages and two disadvantages of inorganic fertiliser.
4. Name the method of application best suited to (a) orange trees and (b) maize planted in rows.
5. Why should fertiliser be covered with a little soil after application?

Assignment

1. List four types of organic manure with one use of each, then write a short comparison of organic manure and inorganic fertiliser under speed, cost and risk.