Soils - More Complex Than I Thought...

So, one of the first things I learned about truffles is that they prefer alkaline soils. In other words, they like soils that are NOT acidic. Soils that are at least 7.5ph, maybe even up to 8.5ph.

So I started doing some Googling and found that the government does a bunch of soil testing, including for ph.

This map shows the surface soil ph for Victoria.
This is the Australian Soil Resource Information System. I can't fidure out how to work it, but I think it contains all the soil information for the country. It's made by the CSIRO, which makes me trust it. If only I could figure out how to get information out of it..

Anyway, lets start with the basics.

My research tells me that soil is made up from three basic components: sand, silt and clay.
The mix of these elements yields different soils.
More clay = a clayey soil.
More sand = a sandy soil.
More silt = a silty soil.
An equal mix = a loamy soil.

Loamy soils are preferred for agriculture. According to Wikipedia, loamy soils "generally contain more nutrients and hummus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils"

Hummus, I'm sad to tell you is not the tasty dip made with chick peas, once again according to Wikipedia, "in soil science refers to any organic matter that has reached a point of stability, where it will break down no further".

So, what I'm looking for is a loamy soil with a high ph, in a region with high rainfall, that won't experience too much change in rainfall over the next 100 years or so.

Clearly I need to do more research...