The rich farmland of the Montreal lowlands owes its existence to deposits left behind after the most recent glaciation and to the subsequent marine incursion known as the Champlain Sea and the bodies of water that succeeded it. In any given climate, soil formation is a function of the types of materials responsible for its development. Bedrock and till are poorly drained, contain little organic material, and are characterized by an abundance of surface stones and boulders; these materials do not generate the same type of soil as fine, easily worked sediment and support different crops.
From the ice age to the present day: the story of soil formation
In general, today's crops are an accurate reflection of the main types of deposits first laid down over 20 000 years ago. A practiced eye can deduce certain facts about the recent geological history of a region by looking at the crops in the fields.
Relatively unaltered bedrock is not conducive to growing crops and is dominated by forest vegetation. Although glacial till is difficult to cultivate because it consists of sand and clay mixed with stones, it produces beautiful sugar bushes and pasture land. The first European immigrants commonly used this type of land as a source of firewood or cleared it to pasture their animals. Farmers who clear stones from their fields know that this is a never-ending task! New stones surface every spring, particularly after a period of intensive freeze-thaw cycling.
Pasture land and forest on very rocky till. (Courtesy of QGC)
After the glaciers melted, the waves of the Champlain Sea sorted the materials left behind, removing fine particles of sand and clay. The finest particles were carried offshore and deposited as clay, whereas the sands and gravels accumulated along the shorelines. Soil that develops on these sands and gravels is ideal for growing apple trees.
Growing apples on gravelly sandy soil. (Courtesy of Pierre Bédard (UQAM))
Heavy clay plains are suitable for grain crops, particularly corn and barley, and for growing soybeans and tomatoes. Sandier plains, with soils that are lighter and more easily worked, are suitable for small fruits, including strawberries and raspberries, as well as potatoes, asparagus, and tobacco. Finally, black soils with high organic content have facilitated the boom in market gardening.
Corn in sandy silty soil (Courtesy of Pierre Bédard (UQAM))