Surface irrigation system

Surface irrigation is yet another common method of irrigation system that you could install on your farm to compensate for the low rains that has been experienced for quite some time.

This type of irrigation system, supplies water from an overhead position. The common method of surface irrigation is the sprinkler irrigation system.

The sprinklers rotate, distributing water to the plants on your farm from above the plants canopy. However, rest assured that you will find a variety of sprinkler irrigation systems from major irrigation equipment suppliers in Kenya.

Surface irrigation system is may be used for many crops like maize, beans, vegetables and other types of plants that require much water on different types of soils in various types of land slopes.

The system is best suitable for irrigating sandy soils at different slopes. This is because sandy soils have high filtration rates thus much water is needed to irrigate the land.

Sprinkler Irrigation System

Sprinkler irrigation system is best suitable for shallow soils that do not require proper leveling, areas with steep slopes with high washing of soil .i.e. erosion and high valued crops.

             Advantages of surface irrigation system

• Much water saving since side movement or percolation of water can be avoided by constructing terraces.
• Land leveling is not necessary thus reducing the leveling costs.
• It can be practiced in areas with non uniform slopes.
• It can be practiced in areas where water is limited or scarce.
• Pesticides and chemical applications can be done together with routine application of water.
• Uniform application of water can be made in high porous soils

Precautions required while installing surface irrigation system

These are the points in which the farmer must consider before installing the surface irrigation systems to ensure proper budgeting and operation of the system.

• Sprinkler irrigation system requires clean water to prevent the blockages of sprinkler nozzles.
• It requires high technical personnel to operate and maintains the system.
• Areas with strong wind are not advisable. This because the wind strength can blow away the system
• Pipe laid on the soil can interfere with other farms of operation like plowing and harrowing purposes if not properly installed.
• General operating cost is high.

Design and installation of surface irrigation system.

These are the part of the system in order for the system to operate normally.

• Screen or debris filter.

  It is used when the surface water is the main source of water for irrigation. The main function of the screen is to filter out the large solid particles that may block the sprinkler nozzles.

When irrigation water is comes from streams, open ditches and wells having silts, the desilting basins are used to trap out the silts instead of using the screen or disc filters.

• Pumping Unit.

  Since the sprinkler irrigation water requires high pressure to provide water over the plants pumping unit is highly recommended to achieve this task.

The pressure forces the water though sprinklers or through perforations or nozzle in pipeline and then form a spray. A high speed centrifugal pump is used when the distance from the pump inlet to the water surface is less than eight meters.

For pumping water from deep wells or more than eight meters a turbine pump is highly recommended. The pumping driving unit may be either motor or an internal combustion engine.

• Piping and tubing.

  The tubing consists of main line; sub main line, laterals and risers. Main line conveys water from the source and distributes it to the sub main line.

The sub main lines convey water to laterals which in turn supply water to the sprinklers. HDPE pipes and PVC pipes are usually used as main lines and sub mainlines for the buried and surface systems.

• Pipe connectors.

  These are the pipe connectors that are used to quickly and easily join and disconnect pipes.

Pipe connectors should provide a reuse and flexible connection, be water tight, be simple and easy to join and disconnect, be light, non-corrosive and durable.

• Sprinkler head. Sprinkler head supplies water uniformly over the field without runoff or much waters loss due to side movement or percolation.

Different types of sprinklers are available. They are either rotating or fixed type. The rotating type can be used in various applications and spacing.

Sprinkler heads are effective with pressure of about 10 meter to 70 meters head at the sprinkler. Working pressure of most sprinkler heads range from 16 meters to 40 meters head are the commonly used and practically achieved.

• Fittings and accessories

  . The following are some of the important fittings and accessories used in sprinkler irrigation system for connection and flow measurements.

1. Water meters. It used to measure the amount of water delivered.
2. Flange, coupling and nipple used for proper connection to the pump, suction and delivery.
3. Pressure gauge. This is used to measure whether the sprinkler is working at required pressure to ensure uniform water application.
4. Bends, tees, reducers, elbows, hydrants, valves and plugs

Flood irrigation

In flood irrigation, water is channeled to the field by use ditch or pipe and allowed to flow over the soil surface through the crops. Even though this method is simple, this irrigation type has negative effects on the crop and soil, using both water and labor inefficiently.

With flooding, only half of the applied water is actually used by the crop. The other half is lost to evaporation, runoff, infiltration of uncultivated areas, and transpiration through the leaves of weeds. For this reason, wild flooding is mainly used on uneven terrains to irrigate pasture, hay, and small grains, which are not affected by sufficient water.

An important aspect to consider in wild flooding is that it’s a great solution to irrigate land that cannot be managed by other irrigation methods.

Basin Irrigation

As the most common type of surface irrigation, basin irrigation is the most ancient and most simple of irrigation types. Basin irrigation requires a leveled soil surface and a narrow ridge 15 to 50cm high on all sides of the field which will serve as the basin.

This type of irrigation is used in the growth of paddy rice, herbs and maize

The irrigated field is divided into smaller areas surrounded by small levees. Water is applied into each basin by various pipes and siphons, or through the levee. Water is removed from the field with surface drains on the low contour levee.

Basin irrigation is suitable for use on moderate to slow intake soils and deep-rooted, closely spaced crops such as maize, grains, cotton, or orchards. Crops that do not tolerate flooding and soils subject to crusting can be basin irrigated by furrowing or using raised bed planting.

Despite its effective method of leaching salts from the soil profile into the deeper groundwater, basin irrigation does have some limitations:

• Leveling the field surface may create a financial and labor issue for the farmer
• Soil tillage is limited due to the small field area
• Levees can be easily destroyed by the entering of farm equipment into the field
• Challenging maintenance of narrow ridges (levees) along the field sides.

Basins range in size, from those designed to irrigate individual trees or small areas of vegetable crops, to rice paddies that occupy several acres.

 Border Irrigation

Border irrigation is the type of flood irrigation which works on the principle of basin irrigation. Water is applied to the field through wide borders. The area between borders is border strip, on which crops grow, and may range from 3-30 m (10-100 feet) in width. To manage border irrigation, the border surface must be leveled across its width so the water can spread uniformly across it.

Sloping borders are suitable for all crops, including grains, alfalfa, and tree fruits. Those that are sensitive to excessive water and soil that is too wet may not be appropriate to irrigate using this method

Furrow Irrigation

Furrow irrigation is an irrigation method in which water is applied from open ditches or pipes through small channels, or furrows, along the field. As water flows through the channel, it infiltrates into the soil, thus irrigating crops. According to furrow direction and level, they can be classified into:

Furrow irrigation is suitable for crops sensitive to too wet soil and excessive water over the stem. Furthermore, crops not suitable for flood irrigation can be irrigated with the furrow irrigation method.

Although this method doesn’t require special farm equipment and can minimize irrigation costs, furrow irrigation does have disadvantages. These include:

• Labor intensive
• High accumulation of salts in the furrows
• Difficult passing of farm equipment across the furrows
• Furrow surface needs to be leveled
• Requires experience on the part of the farmer to divide water into each furrow and to maintain the correct flow rate
• Difficult to automate the system.