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| Final Report
Summary |
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It is hard to overstate the importance of water in the Australian sugar
industry. Not only is water the most important factor limiting yields in the
industry, it is the means by which nutrients and pesticides are transported
below the root zone and off the farm. Community concerns over off site
impacts and over the large amount of water used in agriculture, have
increased during the life of this project. The project focussed on regions
with limited water to tackle issues identified by the grower community.
These concerns were largely to do with production and water use efficiency
issues rather than environmental ones but the technology developed during
the project will also reduce off farm impacts once it gets fully
implemented. The two major issues addressed in the project, the timing of
limited water and yield response to increased allocation, are as current as
ever. Recent dry years particularly in the central region have again
focussed attention on the importance of using limited water at the right
time and on investing in increased water supply. A water recycling project
in that region has made extensive use of the water production functions
developed during the project. The capability developed during the project to
apply water at the optimum time has been well received and has the potential
to assist growers with seasonal planning of water use and to ensure that
they use all their allocated water each year. Full and timely use of limited
water will undoubtedly increase yields substantially when this technology is
understood and applied on a wide scale.
Timing of limited water
Timing of limited water use was the main concern for growers and for the
research during the first three years of the project when it was funded
mainly by the Rural Water Use Initiative (RWUEI) of the QDNR&M. Two
replicated experiments were established in October 2000 on private farms in
the Bundaberg and Childers regions. The trials were designed in conjunction
with the Bundaberg and Childers management committees of the Rural Water Use
Efficiency Initiative (RWUEI). These committees selected the same four
treatments for each trial. Two treatments were designed to compare what
growers could produce from their limited water, with what scientists and
their computer models could produce with the same limited water. An
optimisation procedure called WaterSense, based on the APSIM Sugarcane
model, was developed by the research team for the competition umpired by
the RWUEI committees.
The competition was a draw with equal yields and sucrose content in the
first year, superior grower results in the second and superior WaterSense
results in the third. Despite the difficulty in explaining the relatively
low yields of the WaterSense treatment in the second year, the growers
involved were impressed with the skill of WaterSense. The RWUEI extension
officers and committee members from both Bundaberg and Childers requested
that the scheduling tool be made available for general use.
WaterSense on the Web
The development of the web tool was fully described by Inman-Bamber et al
(2004). Computers at CSIRO Davies lab in Townsville store historic climatic
data obtained from the Bureau of Meteorologys SILO database. These
computers down-load current climate data every day from four AWSs operating
in the Bundaberg/Childers region. One computer contacts a CSIRO server in
Canberra at 10 min intervals to see if anyone has requested a job. The
Canberra server supports the web pages which are used to enter details about
the paddock, to check or alter rainfall and to initiate the necessary APSIM
simulations which take about 40 min for each paddock. The subsequent
optimisation is completed rapidly and an email is generated and sent
immediately to the user. As far as is known this type of irrigation
scheduling optimisation technique that was developed and tested
experimentally for sugarcane has not been reported before, certainly not in
sugarcane. A process is now underway to explain WaterSense to interested
cane growers and advisors. Operation and presentation will be changed after
consultation in order to improve the usefulness and accuracy of this tool.
Water production functions
In 2001 to 2003 experiments were conducted at Kalamia in the Burdekin to
test the water production functions generated by the APSIM model which have
been used extensively for decision support in irrigation and on-farm storage
planning (Lisson et al, 2000). Allocations of 2, 4, 6, 8, and 10 ML/ha were
scheduled by WaterSense so that each allocation was used in the best
possible way. Well irrigated plots started to lodge in February in both
years. Cane yield in February 02 was reduced in the low allocation
treatments but by the June 02 only the 2 ML treatment had a reduced yield.
All other treatments yielded about 140 t/ha. Lodging increased linearly with
allocations up to 10 ML/ha in the 2002/03 experiment. Total aboveground
biomass increased with irrigation up to 8 ML/ha in February 03 but
differences were small and non significant in August 03. There was no gain
in biomass in the fully irrigated treatment over this time while the gain in
the 2 ML treatment was more than double even though irrigation for this
treatment ran out in December 02.
These results have important implications for decisions about investment in
irrigation infrastructure including on-farm dams. Estimates of yield
response and profit from irrigation may be too high when considering
increased allocations resulting from storages particularly in the higher
range of allocations. The phenomenon of lodging and consequent yield loss
due to irrigation increases the risk of investments in supplementary
irrigation in a way that may not have been considered before.
Benefits of the project
The key benefit expected from this project is improved profitability from
irrigated sugarcane due to more efficient timing of use of water and greater
usage of allocated water albeit limited. A second benefit is more efficient
investment in water storages on farm or in securing water allocations from
off-farm sources due to the capability for improved water production
functions produced by the project. A third benefit in some environments will
be less drainage losses and leaching of nutrients resulting from improved
timing of irrigation. An analysis of future benefits from this project by
Agtrans Research indicates that the investment in the project appears to
have been extremely sound. Given the assumptions made for low adoption, the
investment in project CSE001 and part of CSE009 still shows an expected net
present value of $ 1.7 m, a benefit-cost ratio of nearly 2 to 1, and an
internal rate of return of over 9%.
Benefits to the science of sugarcane production include new knowledge
concerning crop physiology and crop modelling. Areas of sugarcane physiology
that have been refined as a result of the project include responses of leaf
and stalk extension to water stress, depth of root water extraction by
sugarcane (up to 2.8 m), root water extraction coefficients and factors
(soil, climate and crop) that favour lodging. The APSIM model has been
improved due to the investment in this project. The project has resulted in
eight publications in the national and international literature. A paper by
Inman-Bamber and Smith (Water relations in sugarcane and response to water
deficits. Field Crops Res. 92, 185-202, 2005) was in the top 10 most
downloaded FCR articles in December quarter of 2005.
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Measuring rainfall, plant growth and radiation in
grower trials in Bundaberg |
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Water production trial with low, medium and high
allocations on left, foreground to background |
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Irrigation workshop March 2004 |
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Journal
papers
Inman-Bamber
NG (2004). Sugarcane water stress criteria for irrigation and drying off. Field
Crops Res 89: 107-122.
Inman-Bamber
NG and Smith DM (2005). Water relations in sugarcane and response to water
deficits. Field Crops Res 92:
185-202.
Park
SE, Robertson MJ and Inman-Bamber NG (2005). Decline in the growth
of a sugarcane crop with age under high input conditions. Field
Crops Res 92: 305-320.
Smith
DM, Inman-Bamber NG and Thorburn PJ (2005). Growth and function of
the sugarcane root system. Field Crops Res
92: 169-184.
Inman-Bamber
N.G. (2004). Sugarcane water
stress criteria for irrigation and drying off. Field Crops Research, 89, 107-122
Inman-Bamber,
N.G., Bonnett, G.D., Smith M.D.
and Thorburn, P.J., (2005). Sugarcane physiology: Integrating from cell to crop
to advance sugarcane production. Field Crops Res. 92: 115-117.
Lisson,
S.N., Inman-Bamber,
N.G., Robertson, M.J. and
Keating, B.A. (2005). The historical and future contribution of crop physiology
and modelling research to sugarcane production systems. Field Crops Res. 92:
321-335
Conference
papers:
Inman-Bamber.
N.G., Attard, S.J.,
Baillie, C., Lawson, D. and Simpson, L. (2005). A web-based system for planning
use of limited irrigation water in sugarcane. Proc. Austr. Sugar Cane
Technol. 27: 170-181
For further information on this project, contact the organisation(s) listed
above,
or SRDC at srdc@srdc.gov.au.
The Industry Links
page on this web site has useful contact details.
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