I worked for ABB Grain for a season, so I know a little bit about the grains and where they are grown.
Firstly, grain variety is of importance to the grower, not the maltster.
That is, unless the marketing man wants to make a deal about it.
Grain varieties are selected and developed to maximise yield for specific
regions, taking into account soil type and rainfall.
The grower then sells the grain to a company and then delivers that grain
to the silo (usually all at the same time, farmers can either contract ahead
or sell on the day). Silos are segregated according to variety and grade,
and the grain is tested on delivery, it can go into 2 or 3 grades of malting
or if it fails the tests can be dropped into feed grades. Feed varieties are always
classified as feed and can never make malting grade even if it passes the tests.
The lowest grade of malt, Malt 3, is often comingled as it is used for specialty malts not base malts (unless they really have to).
The maltster over the next year (depends on how they operate) then receives the barley and malts it. They test the grain and then malt it to the customers specifications. I have been told on several occasions by maltsters that the variety does not matter to them.
Back to your question:
As I said, different areas grow different malting barley varieties and these varieties change over time as better strains are developed.
SA.
Sloop and Schooner are the main varieties. Some Gairdner and Lofty Nijo (exported to Japan only) in the South East, other limited varieties such as Dhow on the Yorke.
VIC
Gairdner, Sloop and Schooner out west are the biggest varieties, some Gairdner too. Franklin and Arapiles are virtually out (only a couple of silos left that will take it).
WA
Stirling, Franklin and Baudin.
QLD
Grimmett and Talon
NSW
Grimmett, Gairdner, prob. still some Schooner.
These are the main varieties anyway.
Cheers,
Brad