Surface irrigation replacement study
A study by the NSW Department of Primary Industries (NSW DPI) has investigated the viability of adopting centre pivot and linear move (CPLM) irrigation systems to replace surface irrigation in the southern Riverina.
NSW DPI researcher, Sam North, based in Deniliquin, said the financial implications of adopting CPLM technology to irrigate winter crops and lucerne for hay were evaluated to address the lack of objective information on the economics of CPLM irrigation.
‘‘We found that CPLM irrigation will be financially viable if the annualised capital costs, plus the associated costs with irrigation, are less than 25 per cent of the projected annual gross income,’’ he said.
‘‘This is reasonably achievable for summer cropping, but careful budgeting is needed before investing in CPLM for winter cropping only.
‘‘In the southern Riverina, achievable target yields on suitable soils with sufficient water and good crop management were found to be six to seven tonnes per hectare (t/ha) for wheat and 18 to 20 t/ha of lucerne.
‘‘Irrigations should be scheduled and applied to maximise yield, so if water is limited, it is better to reduce the irrigated area than to apply sub-optimal irrigation depths.
‘‘Dispersive, heavy clay soils limit the ability to maximise income from a CPLM system as these soils have a propensity to waterlog, reducing the likelihood of consistently achieving maximum yields.’’
Mr North said the number of CPLM irrigation systems in the southern Riverina has been increasing, driven in part by low irrigation allocations and the desire to find irrigation systems that use less water.
‘‘CPLM systems require a large capital investment and are not suited to all soil types,’’ he said.
‘‘In some cases inappropriate and costly decisions have been made.
‘‘Capital costs make up more than half the annual costs of CPLM systems, so the system needs to be able to supply peak crop water demand and be used as much as possible to maximise income.
‘‘Growers also need to be aware of the costs involved in operating these systems and design their machines accordingly, particularly given the rising costs of energy.
‘‘Nationally accredited CPLM irrigation training to help maximise returns is available through NSW DPI’S Profarm program by calling 1800 628 422.’’
The CPLM study was conducted by NSW DPI in conjunction with RM Consulting Group for Murray Irrigation Limited.