Nitrogen Management (June 2013)
Yield and protein data from the 2012 harvest would suggest that the Nitrogen status of many cropping paddocks is low. This is likely to remain the case for 2013 with two exceptions:
Canola paddocks which received high rates of Urea late in 2012. This Nitrogen may not have been used, given the dry finish to the season.
Paddocks with a recent history of legume based pasture. Such paddocks have the ability to mineralise Nitrogen given adequate soil moisture and temperature.
However, for the majority of cropping paddocks, Nitrogen management will require significant attention during 2013. When making topdressing decisions, the following should be considered:
Deep soil testing to 90 cm combined with paddock history data, will allow for more targeted and efficient applications of Nitrogen
Canola requires early Nitrogen to promote root and top growth, increase soil exploration and provide competition with weeds.
Canola crops that did not receive up-front Nitrogen, should be top-dressed ahead of rain within the next 3 to 4 weeks
In wheat, peak demand for Nitrogen occurs between fully tillered and boot stage
Volatilisation losses on acid soils in winter are minimal, even in the absence of rainfall
Rainfall is required to wash Nitrogen into the root zone
Most trials showing high volatilisation losses from spread Urea in the absence of rainfall, have been carried out on bare, alkaline soils with warm temperatures
Urea remains the cheapest form of Nitrogen. Alternative forms of Nitrogen or products that claim to increase the Nitrogen Use Efficiency (NUE) of Urea, can be up to 75% more expensive than Urea on a $/kg N basis. Any potential benefits of these alternatives should be weighed against the extra cost.
The table below shows the differences in concentration & prices of Urea compared to UAN (Easy N).
