Crop Science, Drainage & Irrigation: Farming Essentials

What is Meant by Crop Science?

Crop science is the study of agricultural issues and challenges, including resource use consistent with sustainable production of food, feed, fiber, and fuel, as well as the production, processing, and marketing of high-quality food and non-food products.

Land Reclamation

Land reclamation is the process of improving land to make it suitable for more intensive use. It can also be defined as a process of creating new land from oceans, seas, river beds, or lake beds.

Land reclamation can also refer to the practice of reclaiming or restoring unused wasteland so that it can be utilized for cropping or rearing animals. This may include land that is currently under swamps, rivers, forests, deserts, or infested with tsetse flies.

Land reclamation can also be referred to as reclamation/landfill.

NOTE: There are two main ways of reclaiming land. Drying it out or adding layers to it. The most suitable method will depend on the look of the original land and what the final use of the land will be. To increase the level of the land, the earth can be taken from one place and moved to another, known as dry earth movement.

Methods of Reclaiming Land

a). Deforestation/forest clearance:

This is the process of removing a forest or a stand of trees from the land, which is then converted to a non-forest use. Deforestation may involve converting forest land to farms, ranches, or urban areas.

The land underneath the forest is cleared through the use of bulldozers, motorized saws, axes, or pangas. Controlled burning or arboricides (chemicals that kill trees and herbs) may be used in some cases. After clearing the vegetation and burning, suitable crops are grown, and animals are raised on the land.

However, the indiscriminate cutting down of trees or burning can lead to the loss of this resource.

Additionally, unless the cleared land is properly looked after through terracing or planting, soil erosion will occur.

b). Draining swampy areas:

The main purpose of land drainage is to allow water in the wet or swampy ground to rapidly drain away or to relieve hydrostatic pressure. Ditches are constructed in swampy areas to drain off excess water.

By so doing, the water table is lowered, which facilitates the growing of horticultural crops such as cabbage, tomatoes, eggplants, and onions.

This practice is becoming common in many parts of Africa.

c). Irrigating dry areas:

Irrigation is the artificial application of water to the soil by various systems of tubes, pumps, or sprays.

Arid and semi-arid land, which would not otherwise be used for growing crops, is brought under cultivation by laying on irrigation facilities.

Dams are constructed and water is supplied to crops using overhead sprays, floods, basins, or furrow irrigation systems.

Crop irrigation

d). Terracing hilly lands:

Terracing is an agricultural practice to cross-check that suggests re-arranging farmlands or turning hills into farmlands by constructing specific ridged platforms (terraces).

Sometimes hills are so steep that cultivation is practically impossible unless terracing is done.

Terracing conserves water and soil, and fields become easy to work with machinery.

Methods of terracing that can be employed are broad-based terraces, narrow-based terraces, and bench terraces.

e). Afforestation:

Refers is the practice of planting trees in places where they have died out or never existed before. Trees are planted in areas such as hilltops or slopes of mountains and hills where no or few crops can grow.

Usually, pine and cypress trees are used, for example, Monterey pine (Pinus radiata) and Mexican cedar (Cupressus lusitanica).

Land Drainage

This is a method of rehabilitating land by removing excess water from an area that is waterlogged. The main purpose of land drainage is to allow water in the wet or swampy ground to rapidly drain away or relieve hydrostatic pressure.

The main benefits of draining land are improving soil aeration in areas where waterlogging is a problem. Due to a lack of sufficient oxygen, the roots of most crops become club-shaped. This phenomenon occurs when cabbages are grown under such conditions.

Good drainage helps to raise soil temperature, improve soil structure, and facilitate the growth of certain crops by creating a water table that does not fluctuate much. For example, citrus orchards require good drainage because a fluctuating water table can lead to the death of plants.

Types of Water Drainage

1. Open ditch drainage:

Open ditch drainage is also referred to as a natural drainage system, which consists of uncovered channels or ditches that collect wastewater. This system is designed to handle heavy runoff flows.

The land is excavated to create a ditch, and water flows down the slope due to gravity. This process lowers the water table, making it easier to cultivate horticultural crops and establish permanent pastures.

Ditches can be V-shaped, U-shaped, or square in shape.

Open ditch drainage

2. Tile drainage system:

The tile drainage system is an agricultural drainage system that eliminates excess sub-surface water from fields, creating adequate air space within the soil and allowing proper cultivation and access by heavy machinery for tending and harvesting crops.

Water is drained away from waterlogged areas through tiles or drain pipes laid underground. Although this method is not prevalent in Africa, it is widely used in the U.S.A.

Irrigation

This is an artificial method of providing water to crops in arid or semi-arid areas where there is no rain or where rain is inadequate and/or unreliable. For example, in Egypt, it is possible to cultivate crops in desert areas due to irrigation.

Methods of Irrigation

There are three general methods of irrigating land: surface irrigation, sprinkler (overhead) irrigation, and drip (trickle) irrigation. The selection of which method to use depends on the topography of the land, soil type, availability of water in the locality, and initial and maintenance costs to be incurred by the farmer.

1. Surface irrigation: 

In surface irrigation, water is either flooded over the whole field and is not controlled at all (wild flooding), or water is controlled and directed using basins, furrows, among others. When water is delivered through furrows, the system is known as furrow irrigation, and when it is delivered to crops by using basins, the system is called basin irrigation.

2. Flood irrigation:

In flood irrigation, the whole area is covered with water, which is delivered to crops through ditches. There is little control over the water supplied. This makes it a wasteful system.

3. Furrow irrigation:

This system is most suitable for level soils or gently sloping land where water flows at a slow rate. Furrows, which are constructed on a contour across the slope, allow water to flow slowly by gravity.

No leveling is necessary, but it is important to take care when laying the furrows to prevent soil erosion and runoff.

The furrows should have a consistent gradient of no more than 2 percent from one end to the other. One disadvantage of this system is that salts have a tendency to accumulate in the furrows, particularly if the water used has a high salt content or if there is low or seasonal rainfall.

During the dry season, salts accumulate, and when it rains, they dissolve and cause damage to roots, resulting in insufficient water reaching the ends of the furrows.

4. Basin Irrigation: 

This system is best suited to level soils and soils in which permeability is so rapid that furrow irrigation is impracticable. The system is not widely used in East Africa; it is practiced in citrus growing in South Africa, Florida, and Israel.

There, basins are constructed around one, two, or three citrus trees, and water is brought into the basins via furrows.

Labor costs are low and not much water is used since more than one tree is usually irrigated at ago.

5. Sprinkler or overhead irrigation:

Water is pumped through 20 cm diameter mains to 15 cm delivery pipes called laterals. It is then forced out of nozzles at high pressure into the air.

Waterfalls to the ground in small droplets like rain. Both the mains and laterals are made of aluminium in joints or sections of 5 or 6.7 meters long to make them easy to handle.

Some sprinklers cover a radius of about 25 meters and have a watering capacity of 10 to 25 mm per hour. This method is particularly good on soil with a high infiltration rate.

Sprinkler irrigation

Advantages of Sprinkler or overhead irrigation:

1. No leveling of land is required, which is an expensive item.
2. Soil erosion is minimized.
3. Fertilizers and herbicides can be mixed in the water tank and applied uniformly.
4. Much water infiltrates the soil, and this in turn helps crops to absorb nutrients in the soil easily.
5. It is an ideal method to use in sandy places and hilly areas.
6. No special skill or technical know-how is required to operate this system, for example, when recoupling and uncoupling or moving delivery pipes.

Disadvantages of Sprinkler or overhead irrigation:

1. Topsoil may harden due to the impact of water droplets.
2. High labor costs can be experienced in moving and joining laterals from one part of the field to another.
3. There is a tendency for water not to penetrate deeper layers of the soil profile when it is pumped in small amounts. This tends to limit root penetration.
4. Salts can accumulate in root zones.
5. If the weather is windy, the application of water becomes uneven.

Drip or trickle irrigation method

This is a relatively new method of irrigating crops. It is common in the U.S.A., Israel, and Australia. Water is supplied to each row of crops through polyethylene pipes. The pipes have nozzles at specific intervals through which water drips out.

Advantages of the Drip or Trickle Irrigation Method

1. Water is delivered in or near the root area, thus enabling crops to get plenty of it most of the time.
2. Evaporation and accumulation of salts encountered in surface irrigation are eliminated.
3. Weeds do not encroach on the area between the rows, as water is not spread over the whole surface.
4. It is suitable in areas where there is a water shortage, for example, in dry areas.

Note: The disadvantage of the Drip or trickle irrigation method is that it is costly for irrigating land.

Factors That May Affect The Irrigation of Crops

The irrigation of crops may be affected by several factors, including the type of terrain, as clay soil requires different watering than sandy or silty soil. The weather also plays a role, as hot climates lead to increased evaporation and water requirements. Additionally, the type of crop and its root system, as well as the topography of the terrain and the surface to be irrigated, are important factors to consider.

Conclusion

In conclusion, crop science encompasses a wide range of agricultural practices aimed at sustainable production and the efficient use of resources. One essential aspect is land reclamation, which involves transforming unproductive or underutilized areas into arable land through methods like deforestation, draining swamps, irrigating dry areas, terracing hilly lands, and afforestation. Each technique serves a specific purpose and contributes to expanding agricultural potential.

Land drainage, another important aspect of land reclamation, plays a crucial role in improving soil aeration, raising soil temperature, and creating a stable water table. Open ditch drainage and tile drainage systems are two common methods employed to address waterlogging issues and optimize land productivity.

Irrigation is a vital tool in arid or semi-arid regions where rainfall is scarce or unreliable. Various methods of irrigation, such as surface irrigation, flood irrigation, furrow irrigation, basin irrigation, sprinkler irrigation, and drip irrigation, offer farmers flexibility in water delivery. Factors like soil type, topography, crop type, and water availability influence the choice of irrigation method.

By implementing effective land reclamation techniques and efficient irrigation methods, farmers can maximize their crop yields, improve soil health, and contribute to sustainable agriculture.