IYS Australian Soil of the Month – NOVEMBER

The ‘mystery’ soil competition pit # 6: Brown-Orthic Tenosol

During the year of soils, each month we ask a soil researcher to select his or her favourite soil. Deborah Pritchard is the WA Branch President of Soil Science Australia and Senior Lecturer at Curtin University. Deborah has an Agricultural Science background from UWA and has primarily been involved in teaching agricultural related subjects. She enjoys teaching about soils in a hands-on, practical environment and encouraging her students to understand soils better and be proactive in the health of the soil.

If you had to choose a special Australian soil type what would it be?

Given that a great number of students were involved recently in the National 2015 Soil Judging Competition in Perth, I have selected Competition Pit Number 6 to highlight, a Brown-Orthic Tenosol from the Murdoch University farm at Mundijong. This soil type is common on the coastal plains and minor alluvial soils in south-western Australia. As seen in Plates 1 and 2, this is one of our better quality sands, as distinct from the “gutless sand” that Noel highlighted in May. The site was situated on a crest with a very gently inclined slope (1-3%). The soil has some structure and hasn’t collapsed on the students despite the heavy traffic in and out of the pit. The moderately rapid permeability was demonstrated after heavy rainfall leading up to the competition, which ensured that students did not get wet feet (as they did in another soil type the day before) and promotes the accommodating nature of this beautiful soil type.



Plate 1. Profile of the mystery Soil Pit #6 that was studied intently by many students and judges.  Plate 2. Students involved in the national Soil Judging Competition on 6th September in full action down the mystery soil pit.

What are the main properties of this soil type?

The soil has a weak pedological organisation being a loamy sand grading to clayey >20% Fe gravel at 100cm+. These soils typically have low to moderate water repellence, low to moderate available water storage, moderately rapid soil permeability, neutral to acid soil pH and inherently low fertility. The parent material is typically Aelioan and Residuum deposits. Table 1 outlining the Soil Morphology of the pit in detail as confirmed by the soil judges has been provided by the helpful Henry Smolinski (Ap, A12, B2C) and Gaus Azam.   

Table 1. Soil Morphology of Pit 6

Horizonation Boundary



Colour Mottles











Depth (m)






















A 1   0.13 Abrupt LS 2.5R 3 2 - - - - G -
A 2   0.35 Gradual S 5YR 4 6 - - - - G -
B 1 e 1.05 Abrupt LS 7.5YR 5 6 - - - - G -
B 2 w 1.35 Gradual LS 7.5YR 5 8 - - - - G -
B 3 c 1.50+   LS 7.5YR 6 8 - - 5 F G -


Why do you find this soil type particularly interesting?

This soil type is interesting as it provided much speculation and excitement for the students.  Why is there so much sand? Why does it contains Fe gravel at depth?  How were the Fe gravels formed? Where did the colluvial material come from? Am I in the running for a scholarship to the 2016 NZ-AUS Soils Conference in New Zealand by identifying the profile correctly?






Plate 3. James Macfarlane (Team Curtin) feverishly analysing the soil from the pit during the competition.   Plate 4. Esteemed judges, Gaus Azam (left) and Professor Bob Gilkes (right) at the pit with two student helpers (Photo: Gaus Azam).

Do the properties of this soil type have consequences for its management, e.g. in terms of land use, soil quality, conservation,

The main constraint of this soil type would be water availability, especially over the hot, dry summer months. The soil is particularly good for horticulture if well managed, such as being fertilised, watered, composted and protected from wind erosion.  I lived in market garden country near Jandakot, Perth whilst studying at university and I can clearly remember the above-ground sprinkler system and the regular application of (now restricted) chicken manure. The benefits of a balanced nutrient program is well established on most sands around Perth to provide adequate nutrients for plant growth, whilst preventing leaching and eutrophication issues. In the ‘70s in Perth it was not uncommon for market gardeners to spread dried sewage sludge from wastewater treatment drying ponds as a source of organic matter and fertiliser, although this practice stopped in the late 1980’s!

Can you tell us your most memorable story concerning this soil type?

My most memorable experience on this type of soil was that it was wonderful terrain for horse-riding. There was many good tracks through the bush near where I lived, made more interesting due to  encroaching urban development and associated sand quarries where we could practice being the “Man from Snowy River”. The ground was generally soft if you got bucked off your horse and devoid of nasty rocks. I also had fun digging holes for fence posts for horse paddocks in this soil type as it was easy digging, though had to be done when the soil was damp or the holes collapsed.



Plate 5. Students from the eight University teams negotiating a practice pit on a not so sandy soil type (Photo: Gaus Azam)

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