To determine whether macronutrient supply (phosphorus, potassium, sulfur) becomes limiting as canola growers target high yields with high nitrogen rates in the high rainfall zone of WA.

• Increasing applied nitrogen from 100N to 150N increased yield from 2.8 to 3.2 t/ha and was profitable under both standard and high fertiliser prices. Yield responses up to 200N at least covered fertiliser costs, while increasing to 250N reduced gross margin under high fertiliser pricing scenarios.
• Despite reasonable Colwell P levels in the top 10cm (22 mg/kg), responses to banded phosphorus were evident early in the season. Applying 15 kg P/ha provided yield responses that broke even under high fertiliser prices or were profitable under average prices, while yield responses generally did not justify the significant costs of applying more than 15P.
• Despite yields of 3.8 t/ha with 300N-31P-50K-31S applied, incorporation of manure at seeding or applying high rates of synthetic fertiliser over multiple application timings increased yield by up to 0.5 t/ha, indicating that nutritional deficiencies may still be present even with these high fertiliser rates