SUM20.GK1: GRDC NPK Projects – K Rates, Source and Placement for Canola, Muntadgin


This trial, managed in collaboration with Murdoch University, is part of a series of trials contributing to GRDC Project UWA1801-002RTX looking at ‘increasing profit from N, P and K fertilizer inputs into the evolving cropping sequences in the Western Region’. Here we assess the importance of potassium (K) placement as either MOP or SOP at increasing rates on canola at a sandy clay loam site east of Muntadgin.

Trial Details

Location: Muntadgin

Trial Size: 2.2m x 10m, 20 treatments x 3 reps = 60 plots.

Soil Type: Sandy Clay Loam.

Crop Sown: Bonito Canola, sown 22/04/2020 at 4kg/ha.

Season Rainfall: 179 mm, DPIRD Muntadgin East, 46 mm below long-term average.

Table 1: Pre-trial soil nutrient analysis


Figure 1: Individual treatment harvest yield presented as the mean across 4 replicates. There is a trend of higher yields when MOP or SOP were banded with the seed at rates greaterthan 15kg K/ha.

Figure 2: Comparison of MOP and SOP K rate application yields as an average across all three placements.

Figure 3: Seed oil content in canola seed, with higher oil contents when MOP or SOP were top dressed ratherthan banded with or below the seed.

Figure 4. Returns additional to average gross margin nil control (nil K). Data shows a greater return from banding fertilizer with the seed.

Key Messages

  • Canola utilized high applied K rates with plant K status in the youngest mature leaf ranging from marginal to adequate.
  • Yield averaged 1.9t/ha, fertilizer placement had a greater effect on yields than source, with banding below the seed producing higher yields at rates greater than 30kg K/ha.
  • Top dressing MOP and SOP had higher seed oil concentrations than banding with or below the seed.
  • There is a 12% higher return additional to nil fert when 15kg K/ha MOP was top dressed, and a 15% loss when 75kg K/ha MOP was top dressed.
  • The most profitable treatment was top dressing 15kg K/ha as MOP, returning $1140/ha.

For further information about this trial please get in touch with local Area Manager Kobus Marais