Sur­face ir­ri­ga­tion re­place­ment study

Southern Riverina news - - -

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.

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