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 profiles some of those soils and the flavours they bring.
As well as being attractive, Red Ferrosol soils produce many of Australia’s iconic foodstuffs.
One is ginger from Buderim on Queensland’s Sunshine Coast. Credited with curing everything from flatulence to nausea, ginger would be more a medicine than a food if it did not taste so delicious. The zing from ginger (it is after all in the genus Zingiber) comes from the volatile oils in the rhizome.
There is a strong regionality of ginger flavour and aroma, with the degree of pungency and lemony-ness controlled by the balance of the oils. This balance depends on the growing conditions – weather, management and, of course, soil.
In Australia the main growing areas for ginger are on the North Arm Volcanics near Buderim. This ginger has a very high oil content compared to that from most other countries, with a strong, fresh lemony flavour and aroma, with less pungency. (If you like pungent try ginger from Nigeria).
Rhizome shape, size, degree of branching and extent of rooting are directly affected by soil type and soil acidity. Whilst ginger is very susceptible to waterlogging, periods of low water availability decrease yield and size of rhizomes and makes them more fibrous. So, to get fully flavoured, nicely shaped and big rhizomes you need beaut soil.
As for potatoes grown on the Thorpdale Red Ferrosol, the Buderim Red Ferrosol provides an ideal framework for growing ginger.
This Ferrosol is deep, red, acidic and formed from volcanic parent material. It is much older than the Thorpdale Red Ferrosol though, with the North Arm Volcanics being oozed out around 230 million years ago. Therefore, with more time and weathering intensity, this soil has even less inherited fertility, and an even greater “hunger” for phosphorus. Given that the yield of ginger can be in excess of 150 t/ha of green rhizomes, and that ginger is an annual with very high nutrient demands early in the season, fertiliser requirements are high and efficiency of use is low. This subsequently leads to risks to water resources receiving runoff from these fields. The acidity of the soil also needs to be substantially neutralised to form quality rhizomes, with annual applications of lime required to maintain pH at around 6.5.
A major soil issue for ginger is soil-borne diseases, such as Pythium soft rot. Chemical control of this disease is largely ineffective, and so areas affected can be ruled out for ginger production for years. There has been some promising work on influencing soil biology to increase soil suppressiveness to key soil-borne pathogens, such as desribed by Mike Smith and colleagues. The best approaches appear to be the application of composted chicken manure and sawdust, and moving towards minimum or zero tillage systems. Initially it was thought that the acidity of the soil directly provided some suppression of diseases of ginger, however the study demonstrated that the key is the microbial population that has evolved there rather than the acidity itself.
Confucius used ginger daily to maintain health and intellect, and given Kevin Rudd is from Queensland he is probably a user too. So make yourself smarter, fitter and more philosophical with ginger from the North Arm Volcanics and the Buderim Red Ferrosol.