Land preparation refers to the practice of making land ready and suitable for crop growth. Its aim is preparation of a seedbed. A seedbed refers to a piece of land that is prepared in order to receive the material to be planted.
LEARNING OBJECTIVES
By the end of this lesson, you should be able to:
- Explain the reasons of land preparation
- Explain operations involved in land preparation
- Discuss factors to consider while selecting implements for cultivation
- Describe the importance of minimum tillage
REASONS FOR PREPARING LAND
The following are some major reasons of land preparation:
- To facilitate subsequent farming operations
- To destroy pests and diseases
- To kill weeds
- To improve soil aeration
- To incorporate organic matter into the soil
- To improve water infiltration into the soil
- To improve soil's physical conditions like looseness and depth
- To loosen the soil for easier root penetration and seed germination
- To break hardpan layers and soil capping
- To minimize soil erosion through rolling, ridging and to improve percolation
- To bring to the surface nutrients that were previously leached to lower horizons
OPERATIONS IN LAND PREPARATION
Clearing land
Land clearing refers to the removal of vegetation from the surface of the soil before tillage. Land can be cleared through the following methods:
- Slashing using pangas, slashers and machetes.
- Using chemicals to get rid of the vegetation.
- Winching using a hand operated winch cable.
- Burning
- Mechanical clearing using bulldozers.
- Felling trees using axes.
- Ringbarking trees to kill them before clearing them.
Importance of clearing land before cultivation
- It makes it possible to carry out subsequent farm operations like ploughing, planting and harvesting.
- It helps to destroy the living and breeding sites of parasites like tsetse flies. This explains why land clearing is considered a method of land reclamation.
- It gives way for growing crops.
Primary cultivation
This refers to the operations that are performed in order to initially open up cultivable land that was not previously cropped. This can be accomplished through the use of hand hoes or by mechanical cultivation. Primary cultivation can be done by tractor drawn implements like mouldboard ploughs and disc ploughs.
Factors to consider during implements selection for primary cultivation
- Land topography: In areas where the land is too steep, a jembe or an ox-drawn plough is more appropriate than a tractor drawn plough.
- The desired depth of tillage: Depending on the crop you wish to plant, you can choose either deep or shallow tillage. Where deep tillage is required, heavy tractor-drawn ploughs and subsoilers are more appropriate than lighter implements like jembes and ox-drawn ploughs.
- Soil type: Soils that are heavy, hard and difficult to work on, like clay require heavier implements than lighter soils. Simple hand-held implements tend to dig shallowly on such soils.
- Condition of the land: A forked jembe is more appropriate than a jembe on land that is stony, stumpy or that which has rhizomatous weeds. A disc plough is more appropriate than a mouldboard plough in a field that has obstacles. It is inappropriate to use heavy implements in wet soils. The vegetation cover on the land may also determine the type of implements to use.
- Scale of operation: It is more cost effective to use tractor-drawn implements on a large-sized piece of land than on a small one.
- Skill or know-how required: Some implements like most tractor-drawn implements require special skills to operate unlike some simple hand tools.
- Cost of the implement and the capital available: The cost of certain implements may be very high and this may limit farmers from buying them. The capital available determines whether to hire or purchase implements.
- Power source: The source of power available determines the implement to be used. Draught animals are necessary to operate ox-ploughs while tractor power is necessary to operate mouldboard and disc ploughs. A farmer who lacks both the sources of power may be limited to using hand tools only.
- Availability and accessibility of implements: Implements not easily available may be expensive to acquire through hiring or purchasing.
- Type of tilth required: A disc plough leaves a rough field compared to a mouldboard plough. A Rotavator may be necessary to provide a finer tilth.
Secondary cultivation
Secondary cultivation refers to the subsequent tillage operations carried out after primary cultivation. It is aimed at refining the soil in readiness for planting. It involves harrowing operations using implements like cultivators, hand hoes, rotavators, disc harrows and spring-tine harrows.
Factors that determine the number of secondary tillage operations
- Type of crop to be established: Crops that grow from small seeds require a fine tilth unlike those that grow from large seeds.
- Physical land conditions after primary cultivation: If the seedbed is still rough, more operations are required.
- Moisture content of the soil: Soils that are dry require less operations to conserve the little moisture.
- Land topography: Due to erosion, steep areas, which are very prone, require fewer operations.
- Type of vegetation: The presence of weeds, especially rhizomatous ones, may require more operations.
- Soil types: Heavy and hard clay soils require more operations than softer soils.
Tertiary operations
This refers to the subsequent operations that are carried out after secondary tillage. They are designed to specifically suit certain crops. These operations include:
- Ridging. Ridges are made by digging furrows in a continuous line and heaping soil on one side in order to form a ridge or bund. Ridges are normally made along the contours. They can be made by the use of hand tools like jembes or a ridger drawn by a tractor.
- Rolling. This involves crushing lumps of soil after harrowing and then compacting or firming it. It is done in the production of small-seeded crops like grass, wheat and finger millet. It can be done using simple hand tools on a small scale or by the use of heavy tractor-drawn rollers on large scale.
- Levelling. This involves tearing, crushing and grinding unevenly ploughed soil to produce a smooth well-packed seedbed. Levelling is normally achieved by the use of rollers, harrows and simple hand implements like forked jembes and rakes.
Subsoiling
This refers to deep digging through the subsoil using deep tillage implements. These implements work through the subsoil, hence softening it and breaking the hardpans. Implements mainly used for subsoiling are subsoilers and chisel ploughs.
Minimum tillage
This refers to the application of farming activities that keep soil tillage operations to a minimum. Minimum tillage prepares land for planting without using the conventional or traditional methods of primary or secondary tillage. Some of the farming practices that contribute to minimum tillage include:
- Mulch application to prevent growth of weeds
- Use of herbicides to control weeds
- Planting cover crops
- Planting perennial crops that require little weeding like coconuts, sisal and tea.
- Uprooting, slashing or grazing weeds.
Importance of minimum tillage
- It preserves soil micro-organisms.
- It saves time and labor.
- It reduces the cost of production.
- It minimizes soil erosion.
- It minimizes volatilization of certain nutrients.
- It maintains the soil structure.
