A field scale survey of soil crop relationships on a water repellent sandy gravel soil


Research organisatons
Funding source

Trial details

Researcher(s) Craig Scanlan, Steve Davies, Giacomo Betti and Liam Harte (DAFWA)
Year(s) 2015
Contributor West Midlands Group
Trial location(s) Site 14, Badgingarra, WA
A field scale survey of soil crop relationships on a water repellent sandy gravel soil locations

To quantify the main factors limiting grain yield in a water-repellent sandy gravel soil.

Key messages

Crop establishment and nutrient supply had a greater effect on crop growth than soil water repellence at this site. Interestingly, grain yield showed a weak, slightly positive relationship with our measurements of water repellence e.g. grain yield was highest at points that had higher levels of water repellence (data not shown here). The positive relationship between soil water repellence reflects the role of soil water repellent organic matter and soil nitrogen supply. Our results suggest nitrogen supply was a major limitation to growth therefore it is reasonable that higher grain yields occurred where soil organic carbon (soil nitrogen supply) was high. Water repellence may have had a minor effect because it was not severe at this site; the MED values ranged from 0.1 (Low water repellence, King 1981) to 2.1 (Moderate water repellence) and the average was 1.0 (Moderate water repellence). However, the samples for MED measurement were taken in winter when the expression of soil water repellence is lowest.

Gamma thorium provided a reasonable prediction of shoot K concentration and gravel content and provides a feasible method for delineating K management zones on sandy gravels in the Badgingarra area. Figure 2 shows that high shoot K concentration is associated with gravel content and vice versa. The critical shoot K concentration for wheat at anthesis is 1.5%; based on the data shown in Figure 2 the areas where gamma Thorium is less than 40 ppm would be responsive to potassium fertilizer application.

The gravel measurements separated into 2 clusters; non-gravelly soil where the fraction of gravel was less than 15% by weight and gravel soil where the fraction was greater than 15%. The mean Colwell K 0 to 10 cm was 17 mg kg which is well below the critical range of 51 to 57 for high yield potential on deep grey sands. Based on current prices and a wheat yield potential of 2t/ha, the DAFWA K calculator shows profit would be maximized with 40 kg K/ha applied. However, the efficacy of topdressed K on this sand may be low. The mean Colwell K for the gravel soil was 24 mg / kg which is also well below critical levels but shoot K concentration was adequate. This suggests that the crop is accessing K from the subsoil and that tissue testing may be an important component of assessing nutrient supply from different parts of the sandy gravel landscape.

Lead research organisation Department of Agriculture and Food WA
Host research organisation West Midlands Group
Trial funding source GRDC DAW00244
Related program N/A

Thanks for Graham and Helen Lethlean for hosting the trial. Thanks to Gavin Sarre and Daron Malinowski for their assistance with technical work. This research is supported by GRDC and DAFWA through DAW00244: Delivering enhanced agronomic strategies for improved crop performance on water repellent soils in WA.


Other trial partners Not specified
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Crop type Wheat
Treatment type(s)
  • Crop
Trial type Demonstration
Trial design Unreplicated

Badgingarra 2015

Sowing machinery

Paired row RootBoot seeding points.

Sow date Not specified
Harvest date Not specified
Plot size Not specified
Plot replication Not specified
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Trial source data and summary not available
Check the trial report PDF for trial results.
Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Site 14, Badgingarra, WA Gravelly sand
Derived trial site soil information
Australian Soil Classification Source
Trial site Soil order
Site 14, Badgingarra, WA Chromosol
National soil grid Source
NOTE: National Soil Grid data is aggregated information for background information on the wider area
Actual soil values can vary significantly in a small area and the trial soil tests are the most relevant data where available

Soil properties



Site 14, Badgingarra WA 2015

Observed climate information

Rainfall trial gsr (mm) 340mm

Derived climate information

Site 14, Badgingarra WA


Some data on this site is sourced from the Bureau of Meteorology

SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.

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Trial last modified: 23-07-2019 11:49am AEST