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In 2008, three years of data from field trials at
Yongji and Hongtong were collated to be taken
to the wider farming community as part of the
final year of extension in 2009. At Yongji, a 14%
higher wheat yield was achieved with 18% less
N fertiliser. Optimum applications of N based on
a split application of urea were identified.
In Hongtong county, where traditionally
farmers apply much higher fertiliser rates, the
trials showed the targeted yield of 8.5--8.8 t/
ha of wheat and 8.8--9.2 t/ha of maize could be
achieved by using 47% less fertiliser for wheat
and 61% less for maize, representing savings
of up to $211/ha in a maize crop. The irrigation
in the optimised treatment was also about
20 millimetres less.
"The benefits are not just financial," Dr Chen
says. "That excess, unneeded nitrogen releases
the N2O gases back into the atmosphere, but
for growers to understand the value they have
to see savings for themselves. These people
have little understanding of climate change
and greenhouse emissions.
"However, by 2008 farmers near the
experiment sites were applying N at the same
rates as the optimised treatment."
Professor Xunhua Zheng, a researcher at
the Institute of Atmospheric Physics at the
Chinese Academy of Sciences (CAS) specialising
in agricultural greenhouse gas emissions,
used CAS funding to build automatic and
continuous chamber systems to measure all
three greenhouse gases at the Yongji site---N2O,
carbon dioxide (CO2) and methane (CH4) in
the irrigated maize, wheat and cotton systems.
Preliminary data from the first year of collection
found sprinkler irrigation enhanced N2O
emissions compared with flood irrigation, and
the less irrigation used the fewer emissions.
An internet-based, spatially referenced
software system called a Water and Nitrogen
Management Model (WNMM), developed in
past ACIAR research and used in Australian
agriculture, underpins the four years of research
and extension work. A user-friendly and GIS-
based decision-support system to deliver the
most efficient nitrogen applications for irrigated
crops was developed.
In the first year of the project WNMM was
a focus for Australian researchers, with new
modules added to simulate crop growth,
pasture growth and the impact of grazing and
WNMM was then adopted by the Australian
Cooperative Research Centre for Greenhouse
Accounting for simulating water and N
dynamics and N2O emissions for rainfed wheat
in Victoria and Western Australia and irrigated
pastures in Victoria. These simulations were
compared with N dynamics and ammonia
(NH3) volatisation in South Korea, water and
N dynamics for an irrigated maize and wheat
system in the Yaqui Valley, Mexico, and legume
systems in China.
While the simulation found there was little
difference in N2O emissions in the rainfed
cropping system in Australia with different
stubble management techniques, it found the
main driver for N2O emissions is soil moisture
rather than the availability of N, and when
historic climate data was put into the system
huge variations in N2O emissions in the past
37 years were found. Emissions correlated with
climate variables such as temperature and rainfall
and the N fertiliser application rate. Dr Chen says
the WNMM has been successfully applied to the
irrigated pasture in Victoria, semi-arid wheat in
WA and sugarcane in Queensland for simulation
of N2O emissions. The model can be used in a
variety of farming systems across Australia to
help manage emissions in the future.
"Capacity building has been important in
this project and 12 young Chinese scientists
have been trained to conduct complex
laboratory and field experiments and surveys.
Two WNMM modelling workshops have been
held in Australia and one in China, training
more than 30 people in the skills to use it. This
is vital for good local research to continue,"
Dr Chen says. n
Dr Lin Yuntong and Dr Wan Yunfan with project leader Dr Deli Chen inspecting manual open-top chambers in a maize field.
"The benefits are not just financial ... for growers to understand the
value they have to see savings for themselves."
PROFESSOR DELI CHEN
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