This dataset on total nitrogen presents a surface of predicted nitrogen (X 1000) of layer the top soil (A Horizon) for intensive agricultural areas of Australia. Data modelled from spot observations taken by soil agencies both State and CSIRO. Nitrogen in the top soil is predicted by appealing to the relationship between nitrogen and organic carbon. While the relationship is affected by the assessment methods employed for both, the larger presence of organic carbon observations in the ASRIS database may make for a better organic carbon point model and thus a more stable continental nitrogen model. For details of modelling methodology, see Henderson et al (2001). This map can be used to identify areas where the natural fertility of soils is low and fertilizer inputs would be required to enhance crop production. However, nitrogen measurements are difficult to interpret, without information on the types of nitrogen present and their relevance to crop nutrition (Landon 1984). Total nitrogen is measured as weight % N in the soil (for example, g of N per 100 g soil).

The NLWRA Landuse map was used to identify areas that were cropped for Grains (More information- Landuse Map metadata). Thereafter using the identified cropped area, the area of land under each nutrient category was extracted for each GRDC zone (More information- GRDC Zone metadata).

Data quality: This raster data set has a grid resolution of 0.001 degrees (approximately equivalent to 1.1 km). The data set is a product of the National Land and Water Resources Audit (NLWRA) as a base dataset. Uncertainty surfaces corresponding to ASRIS point model prediction surfaces have been prepared for this soil property. The dimensionless uncertainty values fall in the range 0 to 1000 where lower values represent greater uncertainty (ANRDL, 2001).

Other datasets:

Farm Gate nutrient balance, NLWRA (2001)

Reference- Original metadata

ANRDL (2001) Soil nitrogen for Australian areas of intensive agriculture (derived from site measurements of carbon/nitrogen ratio). Available from: http://asdd.ga.gov.au/asdd/tech/zap/basic-full.zap?&target=brs-4&syntax=html&cclfield1=all&cclfield2=phrase&cclfield3=any&cclterm1=total%20nitrogen&cclterm2=&cclterm3=&start=7&number=1

Henderson, B; Bui, E; Moran, C.; Simon, D.; Carlilie, P. (2001) ASRIS: Continental-scale soil property predictions from point data. Technical Report 28/01, CSIRO Land and Water, Canberra. 107p.