CENTER PIVOT IRRIGATION SYSTEM

BSc. (Hons) Agriculture (Ssp. Aquaculture) Yr2

Agricultural Engineering and Applications (AGRI 2024)

Presented by:Sachin- 1010856Prisha- 1014955Ramonah- 1010211James- 1019087Sevanee- 1010298

IntroductionCenter Pivot Irrigation

It is a form of overhead (sprinkler) irrigation consisting of several segments of pipe (usually galvanised steel or aluminium) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length.

The machine moves in a circular pattern and is fed with water from the pivot point at the center of the circle.

Introduction Cont’dThe center pivot is the system of choice for agricultural

irrigation: low labor and maintenance requirements Convenience Flexibility Performance easy operation

When properly designed and operated, and equipped with high efficiency water applicators, a center pivot system conserves three precious resources: water, energy and time.

Manufacturers have recently improved center pivot drive mechanisms (motors, gears and shafts), control devices, optional mainline pipe sizes and outlets spacing, span lengths, and structural strength.

Pivot Design ChoicesWhen purchasing a center pivot system one must

select: mainline size and outlet spacing length, including the number of towers drive mechanisms application rate of the pivot the type of water applicator

These choices affect investment and operating costs, irrigation efficiency, and crop production.

Wise decisions will result in responsible water management and conservation, flexibility for future changes, and low operating costs.

ELECTRIC POWER DRIVE HYDRAULIC DRIVE PIVOTS

Has two gear reductions: First gear reduction is in the drive

shafts connecting the electric motor to a gear box located at each of the two tower wheels.

The second gear reduction is the gear box driving each wheel.

The maximum center pivot travel speed depends on the:

electric motor speed or rotation in revolutions per minute (RPM);

speed reduction ratios in both the center drive

shafts and gear boxes; and wheel size.

Hydraulic drive pivots have one gear reduction.

Two configurations are used:

A hydraulic motor in each wheel hub

A single motor located at one wheel coupled to a right angle gear drive with a connecting drive shaft that also powers the second wheel.

A hydraulic valve meters oil flow to each set of drives at each tower to maintain system alignment.

Total oil flow is determined by the travel speed, number of drive units (towers), gear reduction, and tire size.

Types Of Drive System

Types Of Drive System ElectricIn electric drive pivots,

individual electric motors (usually 1.0 or 1.5 horsepower) power the two wheels at each tower.

Typically, the outermost tower moves to its next position and stops; then each succeeding tower moves into alignment.

HydraulicWith oil hydraulic drive systems, all

towers remain in continuous motion. The outermost tower speed is the greatest, and each succeeding tower moves continuously at proportionally reduced speeds.

It is a master control valve: increases or decreases oil flow to

the hydraulic motor/s on the last tower.

The required hydraulic oil pressure (1,500 to 1,800 psi) is maintained by a central pump usually located near the pivot pad.

Types Of Drive System

System CapacitySystem irrigation capacity is

determined by the gallons per minute (GPM) and the number of acres irrigated.

System capacity is expressed in terms of either the total flow rate in GPM or the application rate in GPM per acre.

Knowing the capacity in GPM per acre helps in irrigation water management.

Daily and seasonal irrigation capacity.

GPM/acre

Inch/day

Inch/week

Inches in irrigation days

30 45 60 80 100

1.5 0.8 0.55

2.4 3.8 4.8 6.4 8.0

2.0 0.11

0.75

3.2 4.8 6.4 8.5 10.6

3.0 0.16

1.10

4.8 7.2 9.5 12.7

15.9

4.0 0.21

1.50

6.4 9.5 12.7

17.0

21.2

5.0 0.27

1.85

8.0 11.9

15.9

21.2

26.5

6.0 0.32

2.25

9.5 14.3

19.1

25.4

31.8

7.0 0.37

2.60

11.1

16.7

22.6

29.7

37.1

8.0 0.42

2.97

12.7

19.1

25.4

33.9

42.4

Water Applicators in the System

Pads Impact Sprinklers Low Pressure Applicators

• Mid Elevation Spray Application (MESA)• Low Elevation Spray Application (LESA)• Low Energy Precision Application (LEPA)

Pads Low-pressure spray applicators:

flat, concave or convex pads that direct the water spray pattern horizontally, upwards and downwards at minimum angles.

Spray applicator pads: vary in the number and depth of grooves Fine droplets may reduce erosion and

runoff, but are less efficient because of their susceptibility to evaporation and wind drift.

Impact Sprinklers Impact sprinklers:

Installed directly on the mainline and release water upward at 15˚ to 27˚.

Water pattern diameters ranges 50-100 ft. Water application losses average 25-35 % or more.

Low angle, 7˚ sprinklers: reduce water loss and pattern diameter somewhat,

but do not significantly decrease operating pressure.

End guns:• Not recommended- higher volume (GPM) impact

sprinklers with lower application and distribution efficiencies and high energy requirements.

Low Pressure Applicators Operate with low water pressure and work well

with current center pivot designs

Require less energy

Spacing: 60 to 80 inches Nozzle operating pressure can be as low as 6 psi, but more

applicators are required than with wider spacing's (15-30 ft). Water application is most efficient: 16-18 inches above

ground level, spray, bubble or direct soil discharge modes are used.

Evaporation loss:• wind speed,• relative humidity• temperature.

Low Pressure ApplicatorsMid Elevation Spray Applicators

(MESA) Water application:

Above the crop canopy Rigid drops or flexible

drop hoses attached to the mainline gooseneck or furrow arm and extended down to the water applicator.

Nozzle pressure varies depending on the type of water applicator and pad arrangement.

Low Pressure ApplicatorsLow Elevation Spray Applicators

(LESA)

Position: 12-18 inches above ground level Less crop foliage is wet less water is lost to evaporation. LESA spacing 60-80 inches apart,

corresponding to two crop rows.

Nozzle pressure as low as 6 psi is best with the correct choice of water applicator.

Water application efficiency usually averages 85-90 %.

LEPA discharges water between alternate crop rows planted in a circle.

Water application:12-18 inches above ground level (“bubble” pattern or drag socks). Socks help reduce furrow erosion.

LEPA “quad” applicator: bubble water pattern that can be reset to optional spray for germination, chemigation and other in-field adjustments.

95-98 % of the irrigation water pumped gets to the crop.

Low Pressure ApplicatorsLow Energy Precision Applicators

(LEPA)

The Central Tower and The Control Panel Control System

The CP Control System:

Enables handling of the irrigation machine and the programming of irrigation (control of flow, pipeline movement–operation time and speed/time per lap).

A voltmeter and several pilot lights indicate:

• control tension• support tower alarm and luck of

pressure

Automatic starter, position stop device, automatic shut-off and hour counter are included too in a standard CP.

The central Tower:

pyramidal structure (3.5–4.5 m height) galvanized steel angular profiles and anchored on a concrete square platform.

Head of the system: carries all equipment

necessary for the control of the system

The Collector ring The Central Control Panel.

Variable Rate Irrigation (VRI) Technology

VRI technology uses computer maps, global positioning systems, soil sensors and software to control where and how much water the nozzles on a center pivot spray on crops.

The water efficiency of VRI has been tested on farms and found it can reduce the water use in a field by as much as 15% annually without sacrificing crop yield.

Variable Rate Irrigation (VRI) Technology

Irrigation Scheduling ET-Based: Maximum crop

production and quality are achieved when crops are irrigated frequently with amounts that match their water use or ET (evapotranspiration).

Soil Moisture-Based: is highly recommended and complements ET-based scheduling, particularly when there is rainfall during the irrigation season. Devices such as tensiometers, watermark and gypsum block sensors can identify existing soil moisture, monitor moisture changes, locate the depth of water penetration, and indicate crop rooting depths.

Pivot Management Pivot management is centered around

knowing how much water is applied in inches.

A precipitation chart that lists total inches applied for various speed settings on the central control panel is needed.

The length of the pivot is important in determining the flow rate using the equations that follow.

Calculations for length of pivots and 100% water application efficiency

Reduced amounts: LEPA 2-5%, LESA 5-10%, MESA 20%, impact sprinklers 35-40%

Pivot Management

Runoff Control Runoff from center pivot irrigation can be

controlled by changing the optional speed control setting to match water application to soil infiltration.

Agronomic methods: furrow diking (or “chain” diking for pastures), farming in

a circular pattern, deep chiselling of clay sub-soils, maintaining crop residue, adding organic matter, and using tillage practices that leave the soil “open”.

Furrow diking is a mechanical tillage operation that places mounds of soil at selected intervals across the furrow between crop rows to form small water storage basins.

ChemigationChemigation:

Application of an approved chemical with irrigation water through the center pivot.

Improved advanced concept.

Approval of chemicals using irrigation and the instructions are provided on the label.

ADVANTAGES DISADVANTAGES Uniformity of application. Precise application:

chemicals can be applied where they are needed and in the correct concentrations.

Economics: less expensive than other methods and requires small amount of chemicals.

Timeliness: less time compared to other methods

Reduced soil compaction and crop damage.

Operator safety.

Skill and knowledge required: chemicals must always be applied correctly and safely. Chemigation requires skill in calibration, knowledge of the irrigation & chemigation equipments, an understanding of the chemicals & irrigation scheduling concepts.

Additional equipment. Proper injection and safety devices are essential and the grower must be in compliance with these legal requirements.

Chemigation

Fertigation “Spoon-feeding” the

crop. It is very common and has many benefits.

Uses soluble or liquid formulations of nitrogen, phosphorus, potassium, magnesium, calcium, sulphur and boron.

Nitrogen is highly soluble and has the potential to leach.

ADVANTAGES DISADVANTAGES Nutrients can be applied any

time during the growing season based on crop need.

Mobile nutrients such as nitrogen can be carefully regulated in the soil profile by the amount of water applied.

Nutrients can be applied uniformly .

Groundwater contamination is less likely with fertigation because less fertilizer is applied at any given time.

There is minimal crop damage during fertilizer application.

Fertilizer distribution is only as uniform as the irrigation water distribution.

Lower cost fertilizer materials such as anhydrous ammonia often canno

Ammonia solutions are not recommended for fertigation because ammonia is volatile and too much will be lost.t be used.

Many fertilizer solutions are corrosive.

Fertigation

Video Time Nelson water applicator

Video Time Overview of linear pivot

Referencing http://pivotirrigation.blogspot.com/ http://www.traxcoirrigation.com/components http://www.youtube.com/ http://www.youtube.com/watch?v=1L0fGuLXYnA http://en.wikipedia.org/wiki/Center_pivot_irrigation http://www.google.mu/url?sa=t&rct=j&q=center%20pivot%20irrgation

%20system&source=web&cd=11&ved=0CGwQFjAK&url=http%3A%2F%2Fwww.valleyirrigation.com%2Fpage.aspx%3Fid%3D2103&ei=B7hMT6n2FcWi8gPlocnsAg&usg=AFQjCNHljBslQe1R6euQ3s-wDQQ-HXcVrw

http://www.google.mu/url?sa=t&rct=j&q=zimmactic%20irrigation&source=web&cd=10&ved=0CFkQFjAJ&url=http%3A%2F%2Fwww.lindsaymanufacturing.com%2Fpdfs%2FSugarcaneBro.pdf&ei=QLhMT5yNIcTJ8gOwv433Ag&usg=AFQjCNFbK51yr4ynlArrdi57V2mJd9-lxg

http://www.google.mu/url?sa=t&rct=j&q=texas%20center%20pivot%20irrigation&source=web&cd=4&sqi=2&ved=0CDgQFjAD&url=http%3A%2F%2Fwww.extension.org%2Fmediawiki%2Ffiles%2F0%2F02%2FCenter_pivot_irrigation.pdf&ei=bLhMT5quMImk8QPP56XMAg&usg=AFQjCNEP_g7Tnk5YN2-mRSjuM0PFzQiGJg