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Last episode we unpacked what pH actually is. This one asks the better question: why is your number the number it is?

Drive east out of Perth and the pH climbs as the rainfall drops. That is not a coincidence. Leonie walks through the four drivers of soil pH, parent material, rainfall, time, and management, and why only the last one is in your hands. Ammonium fertiliser and every truckload of produce leaving the farm are both acid programs, whether you meant them to be or not.

Then the useful half. Buffering is why a clay shrugs off the same fertiliser program that moves a pale sand a full unit. The nutrient chart is shaped like an hourglass because phosphorus gets locked by iron and aluminium on the acid side and by calcium on the alkaline side. A water pH and a calcium chloride pH are not the same number;  they can differ by nearly a full unit. And an acid result and an alkaline result point you at completely different problems.

If the soil is acid: test deeper, look for aluminium, expect potassium to be walking out. If it is alkaline: check traces, check sodicity, check salt, and stop buying lime.

References are in the episode notes. Thank you to Williams Woolshed in Williams and Naked Bean Coffee Roasters in Albany.

References

Brennan, R. F., Bolland, M. D. A., & Ramm, R. D. (2013). Changes in chemical properties of sandy duplex soils in 11 paddocks over 21 years in the low rainfall cropping zone of southwestern Australia. Communications in Soil Science and Plant Analysis, 44(12), 1885–1908.

Davies, S., Fisher, J., Roper, M., & Murphy, D. (2022). Soil quality: 7. Soil water repellence. SoilsWest / Department of Primary Industries and Regional Development.

Gazey, C., Azam, G., Clausen, J., & Rengel, Z. (2019). Soil quality: 4. Soil acidity. SoilsWest. https://library.dpird.wa.gov.au/sq_ebooks/4/

Hoyle, F. C., & Murphy, D. V. (Eds.). (2017). Soil quality: 1. Constraints to plant production. SoilsWest.

McArthur, W. M. (Comp.). (1991). Reference soils of south-western Australia. Australian Society of Soil Science Inc. (WA Branch).

McKenzie, N., Jacquier, D., Isbell, R., & Brown, K. (2004). Australian soils and landscapes: An illustrated compendium. CSIRO Publishing.

Murphy, B. W. (2015). Impact of soil organic matter on soil properties: A review with emphasis on Australian soils. Soil Research, 53(6), 605–635.

Norton, R. (2020). Potassium and sulphur: Emerging deficiencies in the southern region. GRDC Update Papers.

Stuart-Street, A., Short, N., Galloway, P., & Schoknecht, N. (2025). A simple guide for describing soils (2nd ed.). Department of Primary Industries and Regional Development.

Tang, C., Rengel, Z., Diatloff, E., & Gazey, C. (2003). Responses of wheat and barley to liming on a sandy soil with subsoil acidity. Field Crops Research, 80, 235–244.

Yeates, J. S., et al. (1984), as cited in McArthur (1991).

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You already know your pH. It is on every soil test you have ever paid for. This episode is not rates, products or a lime program. It is what that number is actually measuring.

Leonie starts with a question most of us cannot answer cleanly: what does pH stand for? There are two answers in common use; potential hydrogen and power of hydrogen, and both are useful. One tells you which ion is winning in the soil water. The other tells you the score is kept in multiples of ten. A drop from 6 to 5 is not “one point.” It is a tenfold increase in hydrogen ions.

Then the mechanism. Agricultural lime is calcium carbonate. The part that does the work is the carbonate: it accepts hydrogen ions and turns them into water and carbon dioxide; the same fizz you get in a field acid test, just slowed down over years. The calcium left behind evicts aluminium from the exchange sites, which is often the bigger prize for roots. On some Swan Coastal Plain soils a single application held for about a decade.

pH is the master switch sitting upstream of phosphorus, traces, nitrogen cycling, root depth and water repellence. Next episode: why your number sits where it sits, what buffering is, and how to read an acid result differently from an alkaline one.

References are in the episode notes. Thank you to Williams Woolshed in Williams and Naked Bean Coffee Roasters in Albany.

References

Davies, S., Fisher, J., Roper, M., & Murphy, D. (2022). Soil quality: 7. Soil water repellence. SoilsWest / Department of Primary Industries and Regional Development.

Gazey, C., Azam, G., Clausen, J., & Rengel, Z. (2019). Soil quality: 4. Soil acidity. SoilsWest. https://library.dpird.wa.gov.au/sq_ebooks/4/

McArthur, W. M. (Comp.). (1991). Reference soils of south-western Australia. Australian Society of Soil Science Inc. (WA Branch).

McKenzie, N., Jacquier, D., Isbell, R., & Brown, K. (2004). Australian soils and landscapes: An illustrated compendium. CSIRO Publishing.

Stuart-Street, A., Short, N., Galloway, P., & Schoknecht, N. (2025). A simple guide for describing soils (2nd ed.). Department of Primary Industries and Regional Development.

Yeates, J. S., et al. (1984), as cited in McArthur (1991).

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Part 1 was atoms, charge and the periodic table. This episode puts that chemistry to work in places you already know: soil water, the fertiliser bag, and the spray tank.

Leonie starts with a correction from last week: why potassium and calcium skip ahead on the electron shells, and why that is exactly where the transition metals (iron, manganese, zinc, copper) get their name.

Then the reactions that actually show up on farm:

• Solutions: almost nothing useful happens as a dry solid. It happens dissolved in water.
• Redox: why a waterlogged pit goes grey and rusty orange, and why nitrogen can leave the paddock as a gas.
• Precipitation: two soluble products meet, make an insoluble solid, and that is both blocked nozzles and phosphorus locked up with calcium, iron or aluminium.
• Chelation: the “claw” on a fertiliser label (iron EDTA, zinc EDTA) that keeps a micronutrient soluble long enough for the plant to take it.
• Hard water and glyphosate: calcium and magnesium tying up the herbicide before it reaches the weed.
• Alkaline hydrolysis: why tank pH matters.
• Water repellence:  waxy, non-polar coats on sand grains, and why the molarity of ethanol droplet test works.
• Gamma radiometrics: potassium, uranium and thorium slowly changing under the paddock, and why that signal tracks clay in the top 40 cm.

Salinity, heavy metals (including cadmium in some phosphate fertilisers), organic matter and acidity get a short map, then the series moves to pH next.

If a section does not land, skip it. The next chemical-property episodes will keep using these ideas.

Thanks to Williams Woolshed in Williams and Naked Bean Coffee Roasters in Albany.

Reference list

Chang, R., & Goldsby, K. A. (2016). Chemistry (12th ed.). McGraw-Hill Education.

DeBano, L. F. (2000). The role of fire and soil heating on water repellency in wildland environments: A review. Journal of Hydrology, 231–232, 195–206. https://doi.org/10.1016/S0022-1694(00)00194-3

Geoscience Australia. (n.d.). Radiometrics. https://www.ga.gov.au/scientific-topics/disciplines/geophysics/radiometrics

Grains Research and Development Corporation. (n.d.). Using ground-based EM and radiometrics to map soil amelioration. GroundCover. https://groundcover.grdc.com.au/agronomy/soil-and-nutrition/using-ground-based-em-and-radiometrics-to-map-soil-amelioration

Kabata-Pendias, A. (2011). Trace elements in soils and plants (4th ed.). CRC Press.

King, P. M. (1981). Comparison of methods for measuring severity of water repellence of sandy soils and assessment of some factors that affect its measurement. Australian Journal of Soil Research, 19(3), 275–285. https://doi.org/10.1071/SR9810275

Marschner, P. (Ed.). (2012). Marschner's mineral nutrition of higher plants (3rd ed.). Academic Press.

McKenzie, N., Jacquier, D., Isbell, R., & Brown, K. (2004). Australian soils and landscapes: An illustrated compendium. CSIRO Publishing.

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Most of us left the periodic table behind at school. In the paddock it still matters. A lot.

This is the first of two short episodes that introduce the chemistry you actually need as a farmer, soil scientist or agronomist. We start with the big picture: what the periodic table is really telling us about the elements that end up in your soil, your fertiliser bag and your crop. We’ll look at why some elements stick around while others leach, how parent material sets the chemical starting point for your paddock, and why a handful of elements punch well above their weight in plant nutrition.

No lab-coat language. Just the practical foundation that makes the later episodes on pH, nutrient holding, and fertiliser decisions much easier to use.

Part 2 will build on this and move into the chemistry that sits behind everyday soil tests and management choices.

Thanks to Williams Woolshed in Williams and Naked Coffee Roasters in Albany for your support. You are absolute legends.

References (APA 7)

British Geological Survey. (n.d.). Soil parent material model [Dataset]. https://www.bgs.ac.uk/

Chang, R., & Goldsby, K. A. (2016). Chemistry (12th ed.). McGraw-Hill Education.

Marschner, P. (Ed.). (2012). Marschner’s mineral nutrition of higher plants (3rd ed.). Academic Press.

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What if the nutrition problem, the moisture problem, the pH problem and the non-wetting problem in your paddock are not four separate issues — but one underlying constraint wearing four different hats?

In this episode, Leonie steps back from the individual soil topics and looks at the whole system. Using the simple idea of standing on a hill and surveying the farm, she traces how the fundamental nature of sandy soils (low surface area, low ability to hold water and nutrients) drives a chain of consequences that can leave a crop dying of thirst above two metres of moist soil.

Along the way she unpacks:

• Why leaching, acidification, aluminium toxicity and restricted root growth often belong to the same story
• Why parent material matters more than texture alone (and a real-life garden story that proves it)
• How chemical, physical and biological properties are tangled together rather than sitting in neat boxes
• Four practical habits of mind that help you stop treating symptoms and start aiming at causes

This is not a “how-to” episode. It is the map. The detailed episodes that follow will fill in the boxes. If you finish listening with more questions than answers, the episode has done its job.

A systems view of sandy soils, written for farmers and agronomists who want to spend less money on the wrong fix.

Thank you to Willilams Woolsehd and Naked Bean Coffee for your support.  

REFERENCES 

Davies, S., Fisher, J., Roper, M., & Murphy, D. (2022). Soil quality: 7 Soil water repellence. SoilsWest, Department of Primary Industries and Regional Development. https://library.dpird.wa.gov.au/sq_ebooks/9/

Gazey, C., Azam, G., Clausen, J., & Rengel, Z. (2019). Soil quality: 4 Soil acidity. SoilsWest. https://library.dpird.wa.gov.au/sq_ebooks/4/

Hoyle, F. C., & Murphy, D. V. (Eds.). (2017). Soil quality: 1 Constraints to plant production. SoilsWest. https://library.dpird.wa.gov.au/sq_ebooks/1/

McKenzie, N., Jacquier, D., Isbell, R., & Brown, K. (2004). Australian soils and landscapes: An illustrated compendium. CSIRO Publishing.

Hall, D. J. M., Davies, S. L., Bell, R. W., & Edwards, T. J. (2020). Soil management systems to overcome multiple constraints for dryland crops on deep sands in a water limited environment on the south coast of Western Australia. Agronomy, 10, 1881.

Unkovich, M., McKenzie, D., & Parker, W. (2023). New insights into high soil strength and crop plants: Implications for grain crop production in the Australian environment. Plant and Soil, 486, 183–208.

Soil CRC. (2025). Organic and clay amendments to improve the productivity of sandy soils: Research findings fact sheet. Cooperative Research Centre for High Performance Soils. https://soilcrc.com.au/resources

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CSIRO gave us Wi-Fi, Aerogard, plastic banknotes and the word petrichor (that earthy smell of rain on dry ground).

This week they give us Dr Ben Biddulph.

We're heading into prime frost risk, so I sat down with Ben, Principal Research Scientist with CSIRO in Perth, formerly Chief Scientist of Primary Industries at DPIRD, and one of the country's leading voices on reproductive frost in wheat and barley. He's spent more than two decades on the things that break crops in this climate: frost, drought, heat, waterlogging and salinity. Much of that work has been through national GRDC frost projects.

Because the reason a minus two degree night can cost us 80% of a crop, while our east coast colleagues can get minimal damage at minus six, comes down to a bacterium. Pseudomonas syringae lives on your crop residue, and when it gets cold it builds a protein lattice on the outside of its cell that lines water molecules up so ice can form. Instead of supercooling to minus ten or minus twelve, your crop freezes at minus three. And those little one to two millimetre scuddy showers that roll through at four in the afternoon are delivering high concentrations of it, right before the frost arrives.

In this episode:

• Why frost-prone country has spread from isolated pockets of the central wheatbelt into the Great Southern, the south coast and the north-eastern wheatbelt
• The citizen science project where growers collected spring rain in their freezers
• Why heavy stubble loads increase frost damage, and the rule of thumb Ben's team landed on after three years of work
• What thermography revealed at two in the morning in a paddock — including why ice forms at the bottom of the canopy, not at the coldest point
• Three pieces of myth-busting: nitrogen, copper and potash. Two don't do what growers think. One absolutely does.
• Why barley moved from last crop in the ground to second
• Managing the human side, and why everyone remembers 1998 or 2004

Resources mentioned

• GRDC Frost Tips and Tactics: https://grdc.com.au/resources-and-publications/resources/frost-management/tips-for-identifying-frost-damage
• DPIRD Bulletin 4904 and 4905 — Cereals, Canola and Pulse Frost Identification Guides (available on the DPIRD and GRDC websites)

Thank you to Williams Woolshed in Williams for wardrobe support and Naked Coffee Bean in Albany for keeping me caffeinated.

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In this episode of Agriculture from the Ground Up, Leonie sits down with Professor Kingsley Dixon (one of Australia’s leading plant biologists and restoration ecologists) to explore what Western Australia’s native plants can teach us about our soils.
Kingsley explains how the very constraints that challenge farmers on sandy and duplex soils (extreme infertility, phosphorus limitation, non-wetting, and compaction) are the same conditions that native species like banksias have adapted to over tens of millions of years. Rather than fighting these soils, the plants reveal them, through nutrient-mining strategies, water-gaining microsites, deep root systems that open compacted layers, and a remarkable conservatism in resource use.
The conversation covers practical insights for agriculture, including why native plants thrive where crops struggle, the concept of “cryptic compaction,” the potential of native grain-and-graze species, the importance of soil husbandry over quick fixes, and why biodiversity and biosecurity matter for the future of farming in WA.
A thoughtful, wide-ranging discussion that sits at the intersection of botany, soil science, and real-world agriculture

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Tim Overheu, Principal Research Scientist at DPIRD, returns for round two, and this episode goes well beyond soil types.

We dig into why water holding capacity, not soil classification, is often the real driver behind precision agriculture decisions and why "farming to the characteristic that matters," whether that's pH, organic carbon or moisture, beats farming to arbitrary paddock boundaries. Tim shares a standout example of a farmer essentially "farming his organic carbon," using microbial activity to cut nitrogen inputs while boosting soil and pasture health.

We also cover:

• What EM38 and radiometric mapping can (and can't) tell you about your soil
• Emerging tech, from Bluetooth-connected soil moisture sensors to "lab on a chip" soil chemistry
• Why data collaboration between farmers, researchers and advisors matters more than ever
• A few career "aha moments," including why individual bulk density measurements matter more than paddock averages

It's a conversation about looking past the map to what's actually driving your soil's performance and a reminder that some of the best soil knowledge still comes from people who've simply spent a lifetime paying attention to what's under their feet.

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In Part 2 of our soil texture series, we get practical.

Leonie walks through how to measure soil texture in the paddock using the classic hand-texturing and ribbon test and explains how particle size analysis works in the lab, including the clever physics of Stokes’ Law that lets scientists separate clay from silt.

You’ll also learn how to read the texture triangle, and why the same soil can be given different names depending on which country the research comes from. This international difference in particle-size boundaries is one of the most useful (and most overlooked) things to understand when reading global soil science.

We finish by looking at how texture changes down the profile (uniform, gradational and duplex soils) and the practical decisions texture drives on farm: water storage, nutrient holding, salinity risk and carbon.

A clear, practical episode for anyone who wants to move from knowing the words “sand, silt and clay” to actually using them with confidence.

Reference List 

Barton, L. (n.d.). ENVT2236 Soil Science laboratory manual [Unpublished course material]. School of Agriculture and Environment, The University of Western Australia.

Brown, K., & Wherrett, A. (n.d.). Measuring soil texture in the lab [Fact sheet]. Soil Quality. https://www.soilquality.org.au/factsheets/soil-texture-measuring-in-the-lab

Department of Primary Industries and Regional Development. (2024). Estimating soil texture by hand [Fact sheet]. Department of Primary Industries and Regional Development, Western Australia. https://library.dpird.wa.gov.au/nrm_factsheets/1

Galloway, P., van Gool, D., Stuart-Street, A., Griffin, E., Pathan, S., & Schoknecht, N. (2024). Western Australian soil groups: A diagnostic key to identify soils in Western Australia (5th ed., Resource Management Technical Report 427). Department of Primary Industries and Regional Development, Western Australian Government.

Minasny, B., & McBratney, A. B. (2001). The Australian soil texture boomerang: A comparison of the Australian and USDA/FAO soil particle-size classification systems. Australian Journal of Soil Research, 39(6), 1443–1451. https://doi.org/10.1071/SR00065

National Committee on Soil and Terrain. (2024). Australian soil and land survey field handbook (4th ed.). CSIRO Publishing.

Pluske, W., Boggs, G., & Leopold, M. (2018). Soil quality: 2. Integrated soil management. SoilsWest. https://soilqualityknowledgebase.org.au/soil-texture/

Pluske, W., Murphy, D., & Sheppard, J. (2018). Integrated soil management (Soil Quality ebook series, Book 2). SoilsWest, The University of Western Australia.

Soil Quality. (n.d.). Measuring soil texture in the field [Fact sheet]. https://www.soilquality.org.au/factsheets/soil-texture

Stuart-Street, A., Short, N., Galloway, P., & Schoknecht, N. (2025). A simple guide for describing soils (2nd ed.). Department of Primary Industries and Regional Development, Western Australian Government.

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This episode explains what soil texture really is. Leonie breaks down the three mineral particles that make up texture — sand, silt and clay — and shows that the difference between them is simply particle size.

Key points covered:

• Texture is an inherent soil property that does not change in a human lifetime
• Exact size ranges used in Australia for sand, silt and clay
• Why gravel and stones are excluded from texture
• Why clay has such high surface area and nutrient-holding ability
• How texture groups (sands, loams, clays) and texture grades are named

The episode ends by previewing Part 2, which will cover how to measure texture by hand and in the lab, and an important international difference in particle-size definitions.

New episodes every Wednesday!

Reference List

Brailsford, F., Scanlan, C., Weaver, D., Holmes, K., & Leopold, M. (2023). Gravel soil (Soil Quality ebook series, Book 9). SoilsWest, Murdoch University.

Farm Weekly. (2020, July 14). New guide to understand soil profiles. https://www.farmweekly.com.au/story/6832206/new-guide-to-understand-soil-profiles/

National Committee on Soil and Terrain. (2024). Australian soil and land survey field handbook (4th ed.). CSIRO Publishing.

Pluske, W., Boggs, G., & Leopold, M. (2018). Soil quality: 2. Integrated soil management. SoilsWest. https://soilqualityknowledgebase.org.au/soil-texture/

Pluske, W., Murphy, D., & Sheppard, J. (2018). Integrated soil management (Soil Quality ebook series, Book 2). SoilsWest, The University of Western Australia.

Stuart-Street, A., Short, N., Galloway, P., & Schoknecht, N. (2025). A simple guide for describing soils (2nd ed.). Department of Primary Industries and Regional Development, Western Australian Government.

Connect with Leonie
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Website: www.agriculturefromthegroundup.com.au