1. A review of Centre Pivot and Lateral Move installations in the Australian Cotton Industry
P Smith, J Foley, S Priest, S Bray, J Montgomery, D Wigginton, J Schultz, R Van Niekerk
Review of CPLM installations in the Aust cotton industry – P Smith – IAL conference 2014

2. Introduction
Australian cotton growers aim to maximise profitability per ML
2001 – review of CPLM in the cotton industry (Foley & Raine)
Since then CPLM uptake increased
Australian Government water reforms and funding programs stimulated investment
Healthy Headwaters (Qld) funded repeat study in QMDB in 2011
CRDC funded same in for NSW cotton regions
Surveys combined to examine changes in design, operation and management since 2001
Reporting some results today – full report to be published

3. Survey design and methodology
Format of survey was based on 2001
Designed as face-to-face interview, conducted on-farm
58 selected cotton & grains irrigators interviewed from Southern Qld to Central/Southern NSW
Total 127 CPLM systems irrigating 13,969 ha
42% of area CP, 58% LM

4. Survey format Questions grouped under headings:
CPLM dimensions and configuration
pump and water supply
operation management and problems
sprinkler packages
tyres and wheels
farming system
crop water requirements
application strategies
system performance and productivity
runoff management
agronomic considerations
maintenance
purchase decision making

5. Results and discussion
Number and area of CPLM systems
% are centre pivots compared to 76% in 2001
proportion of area covered by centre pivots has declined by roughly the same percentage
average area under individual systems has reduced for both centre pivots and lateral moves
Centre Pivot
Lateral Move
Number of systems
57 (76%)
18 (24%)
Total Area (ha)
2915 (55%)
2385 (45%)
Mean Area (ha)
~70
~165
Centre Pivot
Lateral Move
Number of systems
121 (66%)
63 (34%)
Total Area (ha)
5901 (42%)
8068 (58%)
Mean Area (ha) 51
139
2001

6. Results and discussion
Yield and Water applied  
Water applied by CPLM approx 30% less than furrow irrigation
Yields similar
Irrigation Water Use Index (IWUI)

7. Results and discussion
Adoption drivers
Main factors labour saving (74%), water saving (62%)
Compared to the 2001, labour saving replaced water saving as main driver
Automation declined a lot: 58% 2001, 24%

8. Results and discussion
Labour requirement :
CP 47% thought labour less than ¼ of furrow
LM 56% thought labour ¼ to ½ of furrow
2001:
CP 69% thought labour less than ¼ of furrow
LM 53% thought labour ¼ to ½ of furrow
: 59% considered higher skill required for CPLM

9. Results and discussion
System capacity
System capacity is important for CPLM design – affects ability to meet crop water requirements
Irrigators were asked for the System Capacity of their CPLM
Check: also calculated from pump flow rate and area irrigated (provided by irrigators)

10. Results and discussion
Design system capacity range 4–32 mm/day
78% CP operators within 1 mm/day of calculated value
46% LM operators more than 2 mm/day from calculated value – probably due to variable area
Difference between stated and calculated Design system capacity (Fig. A: CP, Fig. B: LM)

11. Results and discussion
System capacity
Managed system capacity allows for machine downtime and application losses
Better indicator than Design system capacity

12. Results and discussion
20% of CPLM more than 110% of peak ET (18% 2001)
25% between 90% and 110% of peak ET (36% 2001)
55% below 90% of peak ET
Designed system capacities (left) and Managed system capacities (right) expressed as % of average Peak January ET

13. Results and discussion
System capacity
59% of Design system capacities more than 110% of peak ET (26% 2001)
irrigators are increasingly understanding the importance of adequate system capacity for meeting crop water needs
However, there are now a greater proportion (55%) with Managed system capacity that cannot meet peak water demand (46% 2001) – concerning!

14. Results and discussion
Pressure and costs
Higher running costs of CPLM considered a disadvantage
Should have pressure no higher than necessary
Most systems have pressure regulators 15 psi or less
Commonly recommendation: supply point pressure max 15 psi above regulators ie. Max supply point 30 psi

15. Results and discussion
52% operating above 30 psi – % – room for more improvement
None operating above 50 psi – 13% in 2001

16. Results and discussion
Pressure and costs
Supply point pressure average 19 psi >regulator, range 0–40 psi
21% operating at >30 psi pressure difference
79% have potential to save energy costs

17. Results and discussion
Pressure regulators require min 5 psi above rated pressure to operate properly – 4 systems not operating properly
4 systems 40 psi above regulator pressure

18. Results and discussion
Emitter Systems
Emitter systems changed a lot between 2001 and
LEPA systems reduced 48% to 19%
moving plate sprinklers increased 4% to 54%
May be due to:
slight differences in study participants – more grain in
previous concerns about sprinklers on cotton not eventuating (pollination effects, lint quality)
Change consistent with 2001 report – recommended performance be improved by converting from static to moving plate
Pressure regulators used more widely – 95% v. 58% in 2001

19. Results and discussion
Power Supply and Control Systems
Proportion of diesel powered machines increased – 79% v 65% in 2001
Remaining 21% used mains power – all CP
90% of machines surveyed were electric drives, 10% hydraulic
CP: 53% electric drive powered by diesel generator, 42% electric drive powered from mains, 5% hydraulic drive powered by diesel motor
LM: 71% electric drive powered by diesel generator, 29% hydraulic drive powered by diesel motor
Automatic control use increased – 40% v 10% in 2001
Still low considering potential reduction in labour and increased flexibility

20. Results and discussion
Wheel Rutting and Bogging
64% experienced problems with wheel ruts or bogging – 79% in 2001
Still a prevalent issue – but mostly minor problems overcome within first few seasons  
59% of respondents have or will modify their irrigation strategy or sprinkler set up to help overcome this – most used ‘boombacks’ and half-throw sprinklers around the towers 
Many irrigators commented on need to check tyre pressures and use of different tyre configurations to alleviate bogging

21. Results and discussion
Scheduling
Capacitance probes are the tool most commonly used
2001: generally used one scheduling tool
: used combination of tools – both for furrow and CPLM
CPLM apply less water more often – so operators more conscious of water use under these 

22. Results and discussion
Depth per CPLM irrigation range 5–50 mm, median 24 mm
52% applied 15–30 mm (33% in 2001)
11% fewer growers applied 15 mm or less
7% fewer applied more than 45 mm
Depth applied per pass (Fig. A , Fig. B 2001)

23. Results and discussion
Fertiliser usage 
Fig. A: Change in total seasonal fertiliser use with CPLM fertigation ( )
Fig. B: Change in pre-season fertiliser use with CPLM fertigation ( ) 

24. Results and discussion
Capital cost of CPLM systems
Range $610 to  $6,000 per hectare, median $2,570 per hectare (lowest cost included second-hand equipment)
2001: $1,250 to 2,500 per hectare
70% between $1500 and $3500 per hectare
Large range due to individual site requirements – cost of machine, install machine, pumps, earthworks, electrical works, system capacity, currency exchange rates

25. Results and discussion
Capital cost of CPLM systems
Generally, costs decrease as irrigated area increases
Stronger for LM than for CP
CP: cost for irrigating same area varies by multiple of six
Engage an independent expert to evaluate designs and provide advice!

26. Results and discussion
System Performance
IWUI – discussed earlier
93% of irrigators surveyed had flow meters or pressure gauges for system control
79% used pressure points as an indicator of problems
38% use flow meters to monitor changes or problems in delivery
62% visually assessed emitters 
Only 25% had measured uniformity – range 50% to 100% (90% is benchmark)

27. Thank you!