Results summary: Yield increased from the lowest N rates (150 and 160 kg/ha) up to 190 kg/ha, but there was little difference between rates from 190 to 250 kg/ha. However, the yield increase from 150 to 190 kg N/ha was only about 0.6 t/ha, which given the high N prices in 2022 was not enough to justify the additional fertiliser costs: gross margin was best at the lowest N rates.
This result is in keeping with the results of other N rate trials in 2022, which all found lower optimal N rates than usual. This is thought to be because the mild, dry winter increased mineralisation and reduced leaching such that soil residual N levels were higher than usual at the end of winter.
