Agriculture Reference
In-Depth Information
Figure 1.2
A rudimentary soil
with some root development
on a fractured shale in the
Friuli region of northeast
Italy. The scale is 10 cm.
Soils on Limestone
Retired geologist John Davis (2010) of Pepper Tree winery in the Hunter Valley,
Australia, has said, “Limestone is rare in Australia but it's a key to the greatness of
the famous wine regions of France. When you look at why France is so fantastic at
wine, it's underlain by limestone from one end to the other.”
Although many would challenge Davis's view of the relationship between
great wine and limestone, it is true that limestone is an abundant rock that
underlies many wine regions, especially in Europe. Limestone is a sedimentary
rock formed from precipitated calcium carbonate minerals (chemical composi-
tion, CaCO
3
), or from the calcified skeletons of countless marine animals and
algae deposited in ancient seabeds. The purest form of limestone is the Chalk
formation of northwest Europe, which forms the parent material of soils in the
renowned Champagne and Loire regions of France. Other limestones, such as
in the Dolomitic Alps of northern Italy, have up to half the calcium substituted
by magnesium (Mg) to form dolomite (Ca,MgCO
3
). However, most limestones
have a proportion of impurities such as clay, quartz, and iron oxide particles.
As limestone weathers, the carbonate dissolves to release Ca
2+
and carbonate
