The good earth: Clare Hypercalcic Calcarosol and durum wheat

Australia has some of the world’s most ancient soils, many of which grow delicious produce. In this series, “The good earth”, soil scientist Robert Edis has profiled some of those soils and the flavours they bring. This is the final part.

Durum is the monarch of wheat. Unlike bread wheat - which is used for, well, bread (and sometimes cake) - durum wheat is used to make pasta, couscous, semolina, flat bread and of course burghul, which appears everywhere in Middle Eastern food from tabouleh to kibbeh. The ancestral home of durum wheat is the fertile crescent, including Syria.

Durum wheat is very hard, high in protein, and low in gluten, compared to bread wheat. Australia grows the most reliably high-quality durum wheat. It gets snapped up by Italian pasta makers (more than 50% of our exports of durum wheat are to Italy), as well as local ones like San Remo.

Good quality durum wheat is more valuable than bread wheat, but if the grain size, colour (yellowness), protein and vitreous hardness targets are not met the value plummets. Durum’s flavour and mouthfeel should be a little nutty and crunchy but not gritty. The right soil is needed to get that real Middle Eastern nuttiness.

One soil that fits the bill is the Hypercalcic Calcarosol near Clare in South Australia (which also produces pretty good Riesling). This soil is quite similar to soils in Syria, such as around Aleppo, where durum wheat has grown for thousands of years.

Calcarosols have calcium carbonate throughout the profile, and this keeps the soil pH above neutral. Durum wheat is unsuited to acidic soil - it’s sensitive to aluminium, and that can be released from the soil by acidity. The soil is very alkaline at depth and boron toxicity and salinity are likely to restrict plant growth deep in the subsoil.

“Hypercalcic” means the soil has a calcareous layer where the calcium carbonate is finely dispersed in the soil and doesn’t impede drainage. This is beneficial because durum wheat does not like wet feet. Enough rain falls on Clare that other crops, such as lentils, can be grown after harvest of wheat crops; this builds up soil nitrogen stores for use by the following wheat crop. Durum needs a great deal of nitrogen to make the magic 13.5% protein needed for silky pasta.

Durum wheat is quite new to Australia and ancient in Syria, so Australia has benefitted from Syrian expertise and germplasm. Many varieties of durum wheat grown in Australia have Syrian blood. The headquarters of the International Center for Agricultural Research in the Dry Areas (Australia is an important donor and collaborator) was based in Syria before it had to evacuate due to the war. Now Syria’s capacity to produce quality durum wheat is in tatters. There will, though, be a time for rebuilding, and it will be in Australia’s interests to support restoration of agricultural research and development capability in Syria.

So, enjoy elite pasta, couscous, and burghal, and drink a toast to Syria, the Clare Hypercalcic Calcarosol, and soils in general, perhaps with a glass of Clare riesling. After all, though soils are sometimes dirty and mucky, sticking to shoes and staining knees, mostly they’re just brilliant.

Robert Edis receives, received or hopes to receive funding from GRDC, Incitec Pivot, International Plant Nutrition Institute, MLA, ARC, ACIAR, ARC, ICARDA, Mansfield Shire, La Trobe University, Melbourne University