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Abstract
The potential for improving irrigation scheduling decisions and adoption of more
efficient irrigation systems is explored using a bioeconomic simulation model of lettuce
production on the Gnangara Mound near Perth, Western Australia. Sandy soils with
poor water and nutrient holding capacity are associated with declining marginal productivity
of water at high water use, which would create an incentive to reduce water
use and to adopt closer sprinkler spacing if farmers had correct information about the
declining marginal productivity of water. Incorrect perceptions regarding water–yield
relationships lead to over use of water by up to 50 per cent and reduce profits by
$475
per crop hectare (12 per cent) in the short run, and remove the incentive to adopt more
efficient systems in the long run. Higher water prices create an incentive to reduce
irrigation scheduling time in the short term and to adopt more uniform sprinkler
systems, and tend to reduce the discrepancies associated with poor information about
the marginal productivity of water. The low level of adoption of efficient irrigation
systems in the region might be explained partly by historically poor water governance
and insufficient extension regarding water productivity and technology.