Field Research & Agronomy

SUM20.02: Potassium Rates, Source and Placement, Year 1, Wheat, Badgingarra

Aim

Progressively increasing K rates to optimise returns poses questions of contemporary crop tolerance to chloride (Cl-) associated with muriate of potash (MOP) compared with sulphate of potash (SOP) sources. This trial assesses the importance of K placement as either MOP or SOP, on wheat in 2020, at a sandy site east of Badgingarra at rates designed to run-down, maintain and potentially build K soil reserves over time.

Trial Details

Location: Badgingarra.

Trial Size: 2.2m x 10m, 18 treatments x 3 reps = 54 plots.

Soil Type: Sand

Crop Sown: Ninja Wheat, sown 08/05/2020 at 88kg/ha.

Season Rainfall: 292 mm, BOM Bungulla, 86 mm below long-term average.

**Table 1:** Pre trial soil nutrient analysis

Results

**Figure 1:** *Harvest yield (bars) and grain protein (lines) across four replicates. Yield increased with applied N and P.*

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**Figure 2:** *Comparison of MOP and SOP K rate applications as an average across different placements on the harvest yield. SOP had a stronger yield response to increasing K rates than MOP.*

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**Figure 3:** *Returns additional to average gross margin from nil control (nil K). Data shows a greater return from banding the fertilizer with the seed.*

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Key Messages

Plant growth significantly increased with the interaction between K source, rates and placement.
Yield averaged 3.6t/ha, MOP produced higher yields when banded below the seed while SOP out yielded MOP when banded with the seed.
Protein averaged 11.3% and the greatest treatment differences were seen when fertilizer is banded below the seed, with MOP producing higher protein than SOP.
The most profitable treatment was banding 30kg K/ha MOP with the seed, returning $1,060/ha.
There is a 12% higher return additional to nil fert when 30kg K/ha MOP is banded with the seed, and a 16% loss when 75kg K/ha SOP was banded below.

For further information about this trial please get in touch with local Area Manager Brett Beard, bbeard@summitfertz.com.au.

Wheat