Where no kind of manure is to be had, I think the cultivation of lupines will be found the readiest and best substitute. If they are sown about the middle of September in a poor soil, and then plowed in, they will answer as well as the best manure.
—ColuMella, 1st Century, roMe
Cover crops have been used to improve soil and
of course, is related to managing soil organic matter,
the yield of subsequent crops since antiquity. Chinese
because the topsoil lost during erosion contains the
manuscripts indicate that the use of green manures is
most organic matter of any soil layer. A catch crop is
probably more than 3,000 years old. Green manures
grown to retrieve available nutrients still in the soil fol-
were also commonly used in ancient Greece and Rome.
lowing an economic crop and prevents nutrient leaching
Today, there is a renewed interest in cover crops, and
over the winter.
they are becoming important parts of many farmers’
Sometimes which term to use is confusing. We usu-
cropping systems.
ally have more than one goal when we plant these crops
Three different terms are used to describe crops
during or after our main crop, and plants grown for one
grown specifically to help maintain soil fertility and
of these purposes may also accomplish the other two
productivity instead of for harvesting: green manures,
goals. The question of which term to use is not really
cover crops, and catch crops. The terms are sometimes
important, so in our discussion below, the term cover
used interchangeably and are best thought of from the
crop will be used.
grower’s perspective. A green manure crop is usually
Cover crops are usually killed on the surface or
grown to help maintain soil organic matter and increase
incorporated into the soil before they mature. (This
nitrogen availability. A cover crop is grown mainly to
is the origin of the term green manure.) Since annual
prevent soil erosion by covering the ground with living
cover crop residues are usually low in lignin content and
vegetation and living roots that hold on to the soil. This,
high in nitrogen, they decompose rapidly in the soil.
Photo by Tim McCabe
101
building soils For better CroPs: sustainable soil ManageMent