All plant cells need oxygen, and if clay soils are water-logged, plants will suffer. The poor drainage of clay-type soils is a definite disadvantage. They often warm up very slowly in the spring. This characteristics can mean a delay of a few weeks in planting seeds in a vegetable garden or setting out annual bedding plants, in effect shortening an already limited Prairies growing season by several weeks. Both sandy and clay soils can be enormously improved by the generous addition of organic matter.
Organic matter can consist of compost, well-rotted manure, or peatmoss.
Allowing the original soil and the organic matter to remain layered will result in poor water percolation, excessive run-off, and poor plant growth.