Center pivot irrigation

Water emitters

Water emitters are spaced at distances of 1.5 m to 3m along the pipeline, depending on the sprinkler type and coverage. Modern center pivots irrigation uses Low Energy Precision Application (LEPA) mode. LEPA irrigation methods refer to low-pressure irrigation methods supplying uniform and small-frequent water at or near the soil surface.  These low-pressure irrigation methods in center pivots use angle mist sprayers, bubblers, and sprayers. These three are fit on hose drips hanging from the laterals. Bubblers are placed at the height of 20 cm to 45 cm, while sprayers at 1 m to 1.8 m.

We connect hose drips by gooseneck to the lateral, and the operating pressures range from  0.5 bars to 1.5 bars. The gooseneck and hose drips are connected alternately on the laterals to balance out the stresses on the line. Discharge along the pipeline varies, with more release at the end of the pipeline than near the pivot. We fit gun sprinklers at the end of the pipeline.

Central tower

This is a structure with a height ranging from 3.5 m to 4.5 m anchored to a concrete platform. It uses angular galvanized steel profiles for strength and carries equipment necessary for controlling the system. Equipment carried on the control tower are inlets for fertilizer injection, a control panel, and a collector ring.

Control panel

The control panel enables center pivot irrigation machine handling and programming. It controls the flow, pipeline movement, speed per lap, and operation times of the center pivot. The control panel uses voltmeters to indicate and control tension. A standard control panel comes with an automatic starter, hour counter, and automatic shut-offs.

Wheels

They enable the movement of the pivot mechanism in the farm

A-frame towers

These support the irrigation pipeline above the ground. A-frame towers make use of lightweight galvanized steel or aluminum.

Spare parts for center pivot irrigation

The damaged or worn-out parts in center pivot irrigation need to be replaced as soon as possible for adequate irrigation. There are various spare parts in the market for pivot irrigation. Some of the common spare parts are;

1. Control panel – considered to be the brain of the system. It is attached to the pivot point and gives commands on time to irrigate, what quantities to use, and the speed of rotation.
2. Span – these are long pipes between the drive units. They carry the sprinklers and are connected with the supporting structure of trusses to hold the weight between the A-towers.
3. Tower box – they are located at each drive unit. The work of the tower box is to tell the machine how to move, the direction, and the duration.
4. Pivot point – This is where water enters the pivot pipes and the control panel’s location.
5. Drive unit – the drive unit refers to the part of the pivot irrigation that makes contact with the ground. It is composed of a base beam, drive train, wheels, and various structural supports.

How center pivot irrigation works

Center pivot irrigation can supply water, fertilizer, chemicals, and herbicides. This versatility helps improve the efficiency of irrigation practices by using one machine to perform several functions. Most pivot systems use generators or power from the electrical grid to run the system. The power enables the safety circuit and the forward and reverse movement of the drive unit.

The pivot control panel operates the main functions of the machine. Depending on the control panel, different pivots will have various controls. for instance, when a farmer feeds a command to the control panel, electrical signals travel down the pivot to the last regular drive unit. Afterwards, the control panel directs the drive unit to move forward or backward depending on the instructions. Thirdly, the pivot moves led by the last drive unit until the switch arm connecting the last span to the second last tower is pulled to an angle, activating the next tower.  both towers move, starting tower after tower until the whole system moves. The center pivot system uses two types of sprinklers, i.e., impact sprinklers and spray heads, to supply water as it moves around. The stopping process starts with the tower furthest from the pivot and continues up to the nearest tower.

Pressure ratings of center pivot irrigation

Center pivot irrigation systems need to operate at the correct pressures. High pressures above the designed pressures result in increased operating expenses. Pressures below the design pressures result in uneven water distribution. Reasons for water pressure fluctuations in the system are;

1. Change in groundwater level – decreased groundwater level will result in low pressures in the system.
2. Leaks – occurrence of leaks decreases the water pressure in the pipeline
3. Topography – a downward sloping topography will result in more water at the gun ends, whereas an uphill topography will result in more water near the pivot.

Pressure gauges are installed along the pipeline length to monitor the pressure changes and make it easier to detect issues. Pressure regulation is to control fluctuating pressures in the laterals. They use flow control nozzles and pressure regulators to maintain steady water flow out of the sprinklers.

Flow control nozzles

Flow control nozzles contain a flexible disc that acts as an orifice. When the water pressures are low in the pipeline, the disc remains flat, allowing water to flow freely. As the pressure of water increases, the disc bulges outwards, reducing the opening size. The bulging, in turn, reduces the flow of water through the orifice. Flow control nozzles don’t start controlling water up to pressures of over 35 psi, limiting their use to high-pressure systems.

Pressure regulators

They work by maintaining the present pressure in the sprinklers. In other words, when the pressures are low, the distance between the movable barrel and the fixed seat is large due to the force exerted by the spring. In such a position, the sprinkler flow rate is undisturbed. As pressure increases, the barrel is forced towards the fixed seat, reducing water flow in the sprinklers. Restriction of flow to the sprinkler stabilizes the pressure applied to them, producing a more constant flow rate than inflow control nozzles.

We base the selection of a pressure regulator to use on the design operating pressure of the system. Pressure regulators operate at arrange of 10 psi to 50 psi. When choosing the proper regulator, the operating system pressure should not exceed the regulator pressure by more than 50 psi.

Procedure to undertake when installing center pivot irrigation.

The procedure for the installation of center pivot irrigation is as follows;

1. Land preparation – this process involves activities carried out before assembling the components. Practices done at this time are slope determination, pivot pad construction, and finding the center of the farm.
2. Pivot point assembly – involves the assembly of the pivot point. To fasten the metals together, we make use of bolts and nuts. The technician should tighten the pivot point last.
3. Span assembly – the operating temperatures of water should not go below 2⁰ C, or the machinery will ice up, resulting in failures.
4. Receiver and tower assembly – the technician should follow bolt tightening procedures to avoid structural failure.
5. Electrical – involves connecting the control panel to the electric grid. It would be best if you properly ground the machine before applying power to the main control panel.
6. Machine operation training.

Suitable crops for center pivot irrigation

We mainly use center pivot irrigation for crops that are grown on large farms and are not affected by water on their leaves. Plants like tomatoes are not suitable for irrigating by this method since they are sensitive to water.  Examples of crops grown using pivot irrigation are; sugarcane, orchards, maize, potatoes, small grains, alfalfa, and vegetable crops.

Eunidrip irrigation systems as a supplier of pivot irrigation systems

At Eunidrip irrigation systems, we deal with irrigation equipment, including center pivot irrigation systems. We install and supply the materials needed nationwide. Interested clients can make orders through our online shop, or if they are in Nakuru town, they can always visit our shop.

Other than Center pivot irrigation, we also deal with;

• The entire drip system (All products used and installation)
• Overhead irrigation (Installation and material supply)
• Greenhouse construction
• Solar dryer building
• Net house and shade house construction
• Dam lining
• Borehole drilling

Capital costs and operational cost of center pivot irrigation.

Center pivot irrigation is fully mechanized, automatic, and done on large farms. Capital costs refer to the cost of starting up the scheme, e.g., cost of materials, construction costs, earth movement costs, etc. Operational costs refer to expenses incurred while the pivot irrigation operates, e.g., maintenance and repair costs.  Pivot irrigation has high capital and operating costs; hence, the farmer needs to monitor his/her investment money to ensure the best irrigation choice.

Estimation of annual irrigation costs.

To compute the annual ownership cost, we add the sum of depreciation cost, interest, repair cost, taxes, and insurance in a year.  The repair costs consist of the well cost and pivot costs. Center pivot irrigation uses machinery, and like every other machinery, they depreciate over time. We subtract the salvage cost from the original charges to obtain the depreciation cost. Labor costs and power costs account for the total operational costs in a year.

Large scale irrigation methods

There are four main irrigation types used worldwide, i.e., surface irrigation, sprinkler irrigation, drip/trickle irrigation, and sub-surface irrigation.

Surface irrigation

Surface irrigation involves allowing water to flow naturally by gravity over the land. In this case, there are three main types of surface irrigation methods, i.e., basin irrigation, furrow irrigation, and border irrigation. These methods of irrigation are suitable for areas with clayey soils. Basin irrigation makes use of bunds in a farm. The water floods the areas between the bunds of land. Furrow irrigation uses long trenches to contain the water from water sources. Border irrigation uses water supplied between strips of land using gates or pipes.

Advantages of surface irrigation are;

1. There is easy management, and modern technology is not necessary
2. It is a cost-effective method of irrigating

Disadvantages of using this system are:

1. It requires a lot of water.
2. A farmer cannot use these methods with high infiltration rate soils.
3. There are no drainage outlets.
4. Crops number limitation.

Sprinkler irrigation

This irrigation method involves releasing water to the plants in the form of artificial rain. Sprinklers operate under high pressures, hence the need for pumps. Filtered the water used  to avoid blockages of the sprinkler nozzles. A farmer must regularly maintain the sprinklers for effective water distribution. Some of the maintenance practices are;

1. Regular checking of the washer at the bottom of the bearings
2. Avoiding using lubricants on the sprinkler as it will cause blockages
3. Removing dirt particles from coupling grooves

Advantages of sprinkler irrigation are;

1. It helps in water conservation
2. This method is cost-effective
3. There is uniform water distribution
4. We can use sprinkler irrigation on all terrains.

Disadvantages of sprinkler irrigation are;

1. The system is not suitable for use in windy areas
2. Sprinkler irrigation is not suitable for crops like tomatoes and beans.

Drip irrigation

This method of irrigation utilizes emitters to supply water to the plants. The drip emitters are sensitive to particles; hence clean water is needed. The system makes use of a filter to remove dirt particles from the irrigation water.  The emitters’ spacing is at a fixed distance, having a maximum flow of 2 liters per hour. However, the choice of dripline depends on the plants to be grown. In this case, trickle irrigation is an effective way of conserving irrigation water and is considered a precision irrigation method. Water used mainly flows to the crops using gravity.

Advantages of drip irrigation

1. Soil erosion reduction
2. The system has minimal operational costs
3. There is weed control using this method.
4. Efficient use of water and nutrients
5. Increased crop yields
6. Water flow by gravity reduces the energy cost.

Disadvantages of this system are:

1. The emitters are prone to blockage by dirty water. A farmer can easily solve emitter blockage by cleaning the filters after using them for some time.
2. The initial cost is high.
3. Salinity problems.

Sub-surface irrigation

We can group this system into two, i.e., natural and artificial sub-surface irrigation. Artificial irrigation uses polythene pipes to deliver water directly to the plants in the soil layers. Natural sub-surface irrigation depends on water seeping from streams or lakes to the plants. In other words, the tubes used should be laid at depths of more than 40 cm. The farmer should filter the water to avoid clogging the drip lines.

Advantages of  sub-surface irrigation

1. A farmer avoids water loss by evaporation using this system.
2. There is a high degree of control of irrigation water.
3. This method is applicable in windy and sunny regions.

Disadvantages of sub-surface irrigation.

1. Heavy machinery can damage the pipes.
2. Rodents or root hairs can damage the pipes.
3. There is a risk of emitter clogging

Environmental impact of center pivot irrigation

The world’s population keeps increasing yearly, and the demand for more food increases. Center pivot irrigation can irrigate vast areas helping in food production worldwide. With limited land, irrigation is the best way to ensure adequate food production within the available space.

Center pivot irrigation has a significant effect on the environment. significantly, the irrigation system utilizes a lot of water draining aquifers in areas.  Pesticides and fertilizers are usually used in this system, which can result in water table pollution.

Advantages of center pivot irrigation

1. The automated system reduce labor costs.
2. There is the easy application of fertilizer and herbicides, saving on time and costs.
3. Pivot irrigation is very reliable as the machine covers a large area. Likewise, advanced systems have GIS and GPS systems that determine the right amounts of water to apply in specific places.

Disadvantages of center pivot irrigation

1. This system is not suitable for irrigating rectangular fields alone as some areas will receive insufficient water.
2. The center pivot irrigation systems are costly to install and maintain. This issue and the required land size make the design unsuitable for small-scale farmers.
3. Natural factors such as wind affect water distribution. In short, heat also results in water losses through evaporation, reducing irrigation efficiency.

Maintenance of center pivot irrigation

Lack of proper operation and maintenance of irrigation systems cause problems that can lead to improper water application. Results of improper water application are yield losses, disease spreading, nutrient losses due to leaching, and water runoff. For instance, to effectively maintain center pivots irrigations. Subsequently,  the following practices are essential.

1. The farmer should ensure that the pivot operates at the required pressures for the designated sprinklers. to clarify, this enables the system to avoid damage by excess pressure.
2. A farmer should replace the nozzles after referring to the pivot sprinklers chart. Most importantly, you should choose the right size of the nozzle to ensure the proper working conditions of the sprinklers.
3. Ensuring that the speed of pivot and revolution time correspond with the amount of water required.
4. Before starting the system, a farmer should check for leaks, missing sprinkler heads, and clogged or worn-out nozzles.
5. If working with a variable rate irrigation system, you should check that the solenoid valves are operating correctly and the electronics have not sustained any damage.

In conclusion, by doing all these, center pivot irrigation systems can assure maximum yields.