SPATIAL VARIABILITY IN FOREST WATER USE FROM THREE CONTRASTING REGIONS OF SOUTH-EASTERN AUSTRALIA

Attainable water-use efficiency relates attainable yield, i.e. the best yield achieved through skilful use of available technology, and seasonal evapotranspiration (ET). For wheat crops in south-eastern Australia, there is a common, often large gap between actual and attainable water-use efficiency. To evaluate whether this gap is only an Australian problem or a general feature of dry environments, we compared water-use efficiency of rainfed wheat in south-eastern Australia, the North American Great Plains, China Loess Plateau, and the Mediterranean Basin. A dataset of published data was compiled (n = 691); water-use efficiency (WUEY/ET) was calculated as the ratio between actual grain yield and seasonal ET. Maximum WUEY/ET was 22 kg grain/ha.mm. Average WUEY/ET (kg grain/ha.mm) was 9.9 for south-eastern Australia, 9.8 for the China Loess Plateau, 8.9 for the northern Great Plains of North America, 7.6 for the Mediterranean Basin, and 5.3 for the southern-central Great Plains; the variation in average WUEY/ET was largely accounted for by reference evapotranspiration around flowering. Despite substantial differences in important factors including soils, precipitation patterns, and management practices, crops in all these environments had similarly low average WUEY/ET, between 32 and 44% of attainable efficiency. We conclude that low water-use efficiency of Australian crops is not a local problem, but a widespread feature of dry environments. Yield gap analysis for crops in the Mallee region of Australia revealed low availability of phosphorus, late sowing, and subsoil chemical constraints as key factors reducing water-use efficiency, largely through their effects on soil evaporation.

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Experiments, Environments, and Networks: Commercial Rice Cultivation in South-Eastern Australia, 1900–1945Parts of this chapter were presented at the Natures, Cultures, Identities, Materialities workshop co-organized by Gay Hawkins, Lesley Head, David Trigger and Sarah Whatmore, and at the Australian Historical Association conference at the University of Wollongong in 2013. The comments of participants and audience members greatly helped me to refine aspects of the argument. Sections of this chapter draw on: E.O’Gorman, ‘Growing Rice on the Murrumbidgee River: Cultures, Politics, and Practices of Food Production and Water Use, 1900 to 2012’. Journal of Australian Studies 37, 1 (2013):96–115.

Eco-Cultural Networks and the British Empire : New Views on Environmental History ◽

10.5040/9781474210614.0019 ◽

2015 ◽

Keyword(s):

Water Use ◽

Food Production ◽

Rice Cultivation ◽

South Eastern ◽

Eastern Australia ◽

The University ◽

South Eastern Australia

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Soil water extraction by dryland crops, annual pastures, and lucerne in south-eastern Australia

Australian Journal of Agricultural Research ◽

10.1071/ar00103 ◽

2001 ◽

Vol 52 (2) ◽

pp. 183 ◽

Cited By ~ 65

Author(s):

J. F. Angus ◽

R. R. Gault ◽

M. B. Peoples ◽

M. Stapper ◽

A. F. van Herwaarden

Keyword(s):

Soil Water ◽

Water Use ◽

Crop Management ◽

Water Extraction ◽

South Eastern ◽

Eastern Australia ◽

Soil Water Extraction ◽

The Mean ◽

Dryland Crops ◽

South Eastern Australia

The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.

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