Dr Arjun Pandey1, Prof. James Hunt2, Dr Corinne Celestina2
1The University of Melbourne, Dookie, Australia, 2The University of Melbourne, Parkville, Australia
Biography:
Dr Arjun is a lecturer in crop nutrition and soil science. His research expertise is in soil nitrogen cycling and greenhouse gas monitoring in agricultural systems.
He has held various research roles in universities and industries around the world, including in Denmark, USA and Australia with a research focus on managing soil nitrogen for sustainable crop intensification. He has conducted nitrogen related research in a wide range of cropping systems which include rice paddy, cereal-legume rotation, intensive vegetable production and dairy pasture.
Abstract:
Under-fertilisation of nitrogen (N) in dryland grain crops in southern Australia has led to a significant yield gap and soil organic matter depletion. Growers use a range of different methods for deciding fertiliser-N application rate, such as the APSIM-based Yield Prophet® (YP) decision system and the N bank (NB) system which sets an optimum partial N supply target for an environment. We monitored nitrous oxide (N2O) emission and agronomic performance of the different decision-making systems against the national average (NA) application of 45 kg fertiliser-N/ha and a NIL control in a field experiment at Dookie in Victoria. The NB strategy applied 125 kg fertiliser-N/ha to a wheat crop, whilst YP at 25% probability only applied 16 kg fertiliser-N/ha due to high starting soil mineral N and low growing season rainfall up to the time of decision making. The NB strategy achieved the highest grain yield (6.9 t/ha), followed by YP (5.5 t/ha), NA (5.5 t/ha) and NIL (4.7 t/ha) treatments (at 12% grain moisture, P<0.01, LSD=1.1). The NB strategy also had the highest N2O emission during the season (1.7 kg compared to 0.8 kg N2O-N/ha in NA). N2O emissions in other treatments were similar to NA. However, the NB strategy returned an additional 0.5 t/ha carbon and 13 kg/ha N in above ground residue to plots compared to NA and maintained close to neutral (-2 kg N/ha) partial N balance compared to -52 and -76 kg/ha in NA and YP, respectively, indicating the possibility of soil carbon loss as CO2 in NA and YP.