Nutrient Balances for Australian Natural Resource Management Zones

Understanding the nutrient balance within agricultural systems is an important component of the assessment of long-term sustainability. The data sources to undertake audits are disparate and poorly matched spatially and temporally, and they are not disaggregated by region or use. There are data inconsistencies such that the summed disaggregated data on nutrient use by industry from Australian Bureau of Statistics farm practices surveys indicated 50% more fertilizer used than the aggregated figures supplied by the fertilizer industry. Using IFA fertilizer use by crop data, estimates were made of nutrient removal-to-use ratio (Partial Nutrient Balance) and nutrient partial factor productivity for the major crops in Australia. These data were compared to global estimates using FAO production data and IFA fertilizer use statistics along with IPNI nutrient concentrations.

Partial nutrient balances for N over all cereals in Australia was estimated as 0.82 (global value of 0.67), 0.63 for oilseeds (0.73 global) and 0.93 for sugar (0.89 global). The N estimates do not include biologically fixed N. The P balances were estimated as 0.44 for all cereals in Australia (0.96 global), 0.25 for oilseeds (0.57 global) and 0.92 for sugar (0.84 global). There are refinements to be made to these estimates by using validated nutrient concentrations, improving the quality of the fertilizer use by crop by region data and including recycled materials such as sugar mill wastes or animal manures. Partial factor productivity values were also estimated for the same commodities for each region.

These data have been included as an example of the assessments for N use efficiency in the Global Partnership on Nutrient Management position statement in response to the call for metrics to be included in the post-2015 sustainability goals.