Land Preparation – SS1 Horticulture and Crop Production Lesson Note (Third Term)

Land preparation is the work done to make the soil a good bed for seeds to grow. It has four stages: land clearing, ploughing (primary tillage), harrowing (secondary tillage) and ridging.

Behavioural objectives

1. Define land preparation and give four reasons for doing it.
2. Describe the methods of land clearing used in Nigeria.
3. Explain ploughing (primary tillage) and harrowing (secondary tillage).
4. State the reasons for making ridges.
5. Name the manual and mechanical tools used at each stage of land preparation.

Why is land prepared before planting?

Land is prepared to turn bush or a harvested field into soft, clean, well-drained soil where seeds can germinate and roots can grow.

• Weed removal: clearing takes away weeds and bushes that would compete with crops for water, light and nutrients.
• Soft soil: loose soil lets tiny roots push down easily, but hard soil stops them.
• Better drainage: water sinks in properly and does not stand on the surface to drown the plants.
• Pest control: turning the soil exposes insect eggs and larvae to the sun and to birds, which kills many of them.
• Air in the soil: broken soil lets air reach the roots and soil organisms.
• Easy planting: a levelled, fine soil makes sowing, weeding and harvesting easier.

What is tillage?

Tillage is the breaking up and turning of the soil with tools to prepare it for planting.

• Primary tillage: the first, deep cutting and turning of the soil, called ploughing.
• Secondary tillage: the later, lighter work that breaks clods and levels the soil, called harrowing.

What are the stages of land preparation?

There are four stages of land preparation: clearing, ploughing, harrowing and ridging, done in that order.

Stage 1: What is land clearing?

Land clearing is the removal of trees, bushes, grass and old crop remains from the farm site.

Methods used in Nigeria:

• Manual clearing: cutting grass and small trees with cutlasses, axes and hoes.
• Bush burning: setting dry bush on fire. It is fast and cheap, but it is not the best method.
• Mechanical clearing: using bulldozers or tractor-mounted equipment to push down trees and bush on large farms.
• Chemical clearing: spraying herbicides to kill weeds before cultivation.
• Stumping: removing tree stumps and big roots left in the soil. It must be done before tractor ploughing, or the plough can be damaged.

Effects of bush burning:

• Advantage: it is quick and cheap.
• Advantage: it kills some pests and the ash adds a few nutrients to the soil.
• Disadvantage: it kills useful soil organisms such as earthworms.
• Disadvantage: it destroys organic matter and leaves the soil bare, so erosion is easier.
• Disadvantage: it causes air pollution and the fire can spread to other farms.

Stage 2: What is ploughing (primary tillage)?

Ploughing is the first deep cutting and turning of the soil after clearing.

What ploughing does:

• Buries weeds: they rot underground and add organic matter to the soil.
• Brings up fresh soil: soil from below comes to the surface.
• Breaks the hard crust: air and water can enter the soil.
• Exposes pests: eggs and larvae in the soil are brought to the surface.

Tools for ploughing:

• Manual: a heavy hoe used to dig deep.
• Animal-drawn: a plough pulled by oxen, used in parts of northern Nigeria.
• Mechanical: a tractor with a disc plough, which has large circular blades.

Stage 3: What is harrowing (secondary tillage)?

Harrowing is the breaking of big lumps of soil (clods) left by the plough into smaller, finer particles.

Why harrow:

• Smooth seedbed: small seeds such as pepper and lettuce touch the soil on all sides and take in water well.
• Levelling: level ground stops rain from washing seeds to one corner of the farm.
• Weed control: it uproots small weeds that have sprouted after ploughing.

Tools for harrowing:

• Manual: a hoe or rake used to break clods and level the soil.
• Mechanical: a tractor with a disc harrow. Its discs are smaller and set closer together than those of a plough.

What is the difference between ploughing and harrowing?

Ploughing is the first, deep turning of the soil. Harrowing is the later, shallow breaking of clods into fine soil.

Stage 4: What is ridging?

Ridging is the making of long, raised lines of soil called ridges, with furrows (gutters) between them.

It is common for yam, cassava, sweet potato and maize.

Reasons for making ridges:

1. Easy tuber growth: deep, soft soil lets tubers such as yam grow big and straight.
2. Erosion control: ridges made across the slope stop rain from washing away the topsoil.
3. Easier weeding: weeds in the furrows between ridges are easy to see and remove.
4. Better drainage: extra water runs into the furrows and away from the roots.

Tools for ridging:

• Manual: the traditional Nigerian hoe.
• Mechanical: a tractor-mounted ridger.

What tools are used at each stage of land preparation?

Each stage has a manual tool for small farms and a mechanical tool for large farms.

Evaluation

1. What is land preparation?
2. Give four reasons for preparing the land before planting.
3. Why is bush burning not the best method of land clearing?
4. What is the difference between ploughing and harrowing?
5. State three reasons for making ridges.

Assignment

List the four stages of land preparation in order. For each stage, name one tool used and state its main goal.