Dr Yolanda Plowman1, Prof. James Hunt2, Miss Kate Finger1, Dr Arjun Pandey2, Dr Xiaojuan Wang2, Dr Mark Farrell3
1Birchip Cropping Group, Birchip, Australia, 2University of Melbourne, Melbourne, Victoria, Australia, 3CSIRO
Biography:
Yolanda Plowman is the Senior Research Manager at the Birchip Cropping Group (BCG). Yolanda holds a PhD from the University of Sydney, where she focussed on the soil microbiome associated with wheat. In her role as the Senior Research Manager, Yolanda oversees the day-to-day research program as well as the strategic planning and execution of innovative projects focussed on the agricultural challenges of tomorrow and beyond. Yolanda works closely with the BCG team to ensure that the work carried out aligns with BCG’s mission of improving the prosperity of Australian broadacre farmers through applied science-based research, and extension.
Abstract:
Australian growers typically apply too little nitrogen (N) fertiliser to cereal and oilseed crops, and this can lead to N mining. N mining is the result of a negative N mass balance, which refers to more N leaving a system than what is being returned through fertiliser and legume crops. It is assumed that N mining negatively impacts crop yield, however it is unknown how much of this yield decrease is due to reduced N mineralisation from SOM, and if this can be compensated for within one season through the application of additional N fertiliser. The impact of N mining was investigated in a long-term N management trial at Curyo, Victoria. Prior to this experiment, the trial had been running for five years and contained various N management treatments. The two extreme treatments, Nil top-dressed N and 25% Yield Prophet, sown to canola, were sub-treated with five different rates of N: 0 kg/ha, 50 kg/ha, 100 kg/ha, 150 kg/ha, and 200 kg/ha top-dressed in winter. The extreme treatments contained similar amounts of mineral N, however organic C was significantly higher in the 25% Yield Prophet treatment compared to the Nil (57 N kg/ha and 53 N kg ha, and 6.5±1.1 C mg/kg and 4.6±0.4 C mg/kg, respectively). To achieve the same yield in the Nil, a significant compensation of additional N (80 kg/ha) was required for soil where N had been mined compared to treatments with positive N mass balance. These results show that N mining does reduce yield within five years, however it was possible in this case to compensate for this effect with substantial rates of applied N.