Key Points
- The trial was established to evaluate the optimum nitrogen timings and rates for Amarok gristing wheat, grown under irrigation on a Templeton silt loam.
- The trial at Dorie in Mid Canterbury was characterised by very low soil nitrogen reserves (20kg/ha N in 0 – 60 cm assessed on 15th August) as a result of the extremely wet winter.
- The optimum nitrogen rate (based on margin over nitrogen cost) for a 2 split of nitrogen was 270 kg/ha N applied giving a total of 290 kg/ha N if the 20 kg/ha N soil reserve was taken into consideration. This treatment produced 12.07 t/ha and a 10.3% protein.
- However if nitrogen dose was split equally between three doses, a higher margin was generated from 230kg/ha N applied (250kg/ha N including 20kg/ha N in the soil). This produced a yield 11.49 t/ha and 11.4% protein, the higher protein offsetting the lower yield.
- Though it is difficult to compare the Sirius Wheat Model prediction with other treatments since it applied far more N than any other treatment, this four split approach produced the highest margin over nitrogen cost by virtue of the highest yield 12.39 t/ha and 11.3% protein. The Wheat Calculator treatment applied 396 kg/ha N between GS25, GS31, GS39 & GS51.
- In this irrigated trial there was a consistent lift in grain protein averaging 0.6% when 40kg/ha N of the total dose was applied at ear emergence GS59.
- If the ear emergence dose was increased still further (to a third of the total dose) then protein was increased by 1.1%.
- As a result of the lower soil nitrogen there was evidence that nitrogen timed earlier than the traditional FAR standard timings of GS31-32 followed by GS39 produced significantly higher yields, however the GS30 followed by GS32 timing suffered 0.1% lower protein meaning that margins were little different.
- Applying a late application of 40kgN/ha at GS59 did not produce more yield than when the same amount of N was applied at 2 timings. Protein increased slightly as did margins in this gristing wheat.
- Even with the lower soil nitrogen reserve the best combination of yield and protein came from splitting total nitrogen dose equally into three doses at GS31/32 (1st-2nd node), GS39 (flag leaf emergence) and GS59 (ear emergence).