Americas and Oceania Group - International Plant Nutrition Institute

ensure optimized response to future atmospheric [CO 2 ]. This work was undertaken by Lakmini Thilakarathne
as part of an MPhil program through The University of Melbourne and has been submitted to Functional Plant
Biology for publication.
Water use, as measured by plant transpiration efficiency also alters with higher CO 2 levels, and like
photosynthetic response, there were significant differences between two current wheat cultivars and the more
efficient water user maintained that benefit even under elevated CO 2 . This work was undertaken by Dr. Sabine
Tausz-Posch and has been submitted for publication. Dr. Norton continues to work with graduate students
and research scientists at The University of Melbourne and the Victorian Department of Primary Industries on
these issues as the past project leader. ANZ-02
Nitrogen and Sulfur Sources Affect the Response of Canola in Southeastern Australia
Project Leader: Rob Norton, IPNI, Horsham, Victoria. E-mail: rnorton@ipni.net
Project Cooperators: MT Khan (The University of Melbourne), Robert Edis (The University of Melbourne), Deli Chen
(The University of Melbourne), and Charlie Walker (Incitec Pivot Ltd).
In cropping systems, the importance of N and S nutrition has been clearly established, particularly for
canola. The usual strategy has been to pre-spread gypsum and drill urea in at sowing to meet these demands.
It was hypothesized that the use of ammonium sulfate along with urea may enhance both N and S efficiency
in calcarosol. A field experiment was conducted in 2011 on a sandy soil at Walpeup in the semi-arid north
west of Victoria, an area and soil type that has seen renewed interest for canola production. This experiment
aimed to characterize the agronomic aspects of urea, gypsum, and ammonium sulfate under field conditions.
Nitrogen and S were applied at different rates, in different ratios, and from different products at sowing.
The applied N significantly increased growth and seed yield, and the crop yield increased more with
applied S in the urea plus ammonium sulfate compared to urea plus gypsum strategy. Urea plus ammonium
sulfate significantly increased both agronomic N and S efficiency by 4% and 36%, respectively, compared
to urea plus gypsum. Irrespective of whether derived from ammonium sulfate or urea, N significantly
increased (p ≤0.05) biomass yield and grain yield at flowering stage and maturity stage, respectively. Sulfur
responses were not seen at flowering, but ammonium sulfate showed significant increase of grain, straw,
and grain yield at 20 kg S ha at maturity stage of canola compared to gypsum. Although two sources of N
and S had little effect on growth and yield at the lower rates of N and S, the urea and ammonium sulfate
when applied together increased grain yield (12%) over urea plus gypsum at highest level of N and S. There
was no interaction between N and S rates indicating that the ratio at which these nutrients were applied was
not important in this situation. This research is part of a PhD project undertaken by MT Khan through The
University of Melbourne. ANZ-03
Nitrogen Dynamics Under Elevated Carbon Dioxide
Project Leader: Deli Chen, University of Melbourne Resource Management and Geography, Melbourne, Victoria.
E-mail: delichen@unimelb.edu.au
Project Cooperators: Shukee Lam (The University of Melbourne), and Roger Armstrong (Victorian Department of
Primary Industry).
Elevated atmospheric CO 2 affects growth and yield which then affect processes controlling the supply and
losses of N to sustain these increases. This research was undertaken to measure the effects of elevated CO 2
on crop N demand, fertilizer N recovery, symbiotic N 2 fixation, residual N availability, and greenhouse gas
emissions from cropping systems in southern Australia (Horsham) and northern China using free-air CO 2
enrichment (FACE) facilities and glasshouse chambers. Elevated CO 2 generally increased crop biomass (11
to 84%) and grain yield (10 to 70%) across a range of crops, except when the wheat crop was grown under a
hot and dry period, or when legumes experienced P deficiency. Results in the literature indicate that grain N
removal worldwide is likely to increase by an average of 17% in crops grown under elevated CO 2 .
Wheat was no more effective at sourcing N from fertilizer, so that the CO 2 -induced increase in plant N
uptake (18 to 44%) was satisfied mostly by increased uptake of indigenous N (19 to 50%) at both sites. A
glasshouse experiment showed that incorporating crop residues lowered the recovery from soil. Under FACE
conditions in Changping, elevated CO 2 increased the proportion (from 59 to 79%) and the amount (from
166 to 275 kg N/ha) of shoot N derived in soybean. A glasshouse experiment then showed that the rate of N
fixation in chickpea, field pea and barrel medic under elevated CO 2 depended on P supply, with improved N
fixation to CO 2 occurring only with adequate P supply. Elevated [CO 2 ] increased emissions of N 2 O (108%),
CO 2 (29%) and CH 4 from soil at Horsham, with changes being greater early in the season. At the Changping
site, elevated [CO 2 ] increased N 2 O (60%) and CO 2 (15%) emission, but had no significant effect on CH 4 flux.
56 IPNI Interpretive Summaries