Nutrient Balances for Australian Natural Resource Management Zones

This project continues the ongoing work of the IPNI-ANZ program to develop and present nutrient use and removal data from Australian agriculture. Using currently available data on production and nutrient use, nutrient performance indicators can be estimated at the national level, although these data – and many other estimates – either ignore or over simplify the input of biological nitrogen fixation by selecting a national value derived from crop data only and/or ignoring inter-annual variations. High quality production data is available down to the natural resource management zone [as defined by Australian Bureau of Statistics (ABS)], but there are few sources of good quality fertilizer use by crop data at the regional scale. Different data sources on regional fertilizer use by crop were compared, and while there is some concordance each source has its own problems. The ABS data is not disaggregated by crop and the International Fertilizer Association (IFA) data are only presented by region. The ABS does have some inconsistencies over time concerning the wording of particular questions concerning land management practices. The quality of the data used and a definition of the industry cohort assessed are important in developing reliable and consistent estimates of these nutrient performance indicators.

The assessments undertaken show reasonable consistency in the size and distribution of partial nutrient balances for Australia. In general, Australian agriculture has a near neutral or slightly positive nitrogen (N) balance, a positive phosphorus (P) balance and a negative potassium (K) balance. As a consequence, soil P levels are likely to be increasing, while soil N and K levels are being depleted. These values show large inter-annual variation, with nutrient removals (i.e., production) showing larger variation than nutrient inputs.

Using the data from the regional nutrient budgets, maps were created for three audit periods (2007-08, 2009-10 and 2011-12) and these are posted on the Centre for eResearch and Digital Innovation at Federation University (http://www.ozdsm.com.au/ozdsm_map2.php). The maps have very limited functionality, and there are tentative plans to develop the functionality further, similar to the information provided through the IPNI NuGIS on-line tool.

Similar to the whole of Australian agriculture, the Australian grains industry overall shows a negative N and K balance and a positive P balance, and these values are consistent with the data reported earlier from the international survey by Norton et al. (2014) and the Australian Agricultural Assessment (2001).