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sisters for the prairies: intercropping with wheat, canola
by Tony Szumigalski Ph. D. Candidate, Department
of Plant Science
canola and peas grown together in an intercrop
dont need a degree in nutrition to know about the three
most basic functional food groups - carbohydrates, proteins
and fats. Perhaps as long as 10,000 years ago, early farmers
of the new world (ancient inhabitants of Central America)
could provide a completely balanced diet from three staple
crops: corn, beans and squash (a.k.a. the 'three sisters').
In this system, corn was the major provider of carbohydrates,
beans supplied a large share of protein and squash seeds contained
fats, including some essential fatty acids not found in the
other crops. Native American farmers grew these three crops
together in polycultures (intercrops) realizing that the 'three
sisters' complemented each other agronomically as well as
nutritionally. Since these three crops were so radically different,
they did not use the same resources (e.g., light, nutrients,
water) in exactly the same way and they did not respond exactly
the same to stresses such as diseases pests or drought.
research that we are conducting at the University of Manitoba
borrows heavily from the ancient wisdom of the Aztecs and
Mayans. In fact, the cereal- legume-oilseed theme that we
are following is similar to one that is central to the 'three
sisters', except that we are investigating the benefits of
growing wheat, peas and canola in polycultures on the prairies.
More specifically, we want to determine if and how polycultures
use resources and suppress weeds more efficiently than monocultures.
Four different polycultures made up of the three crops, including
all pair combinations and the triple-crop system, are being
compared to the three monocultures.
results indicate that the wheat-canola-pea triculture and
the canola- pea biculture seem to suppress weeds more consistently
compared to the other systems. However, under certain conditions,
monocultures such as peas performed equally as well or even
better than these polycultures. The performance of the monocultures
was not consistent, however, and one year, the peas may perform
very well and the next year, they may do poorly, but the canola
may 'pick up the slack', etc. This may help to explain why
increasing crop diversity within a single year has long been
known to add a certain degree of stability to a cropping system.
most cases, the polycultures demonstrated a more efficient
use of land and resources compared to monocultures. On average,
it required about 10% more land to grow crops in monocultures
than in polycultures. This may be significant in these times
of expensive inputs and decreasing margins. One reason for
the success of intercrops is that, in general, they tend to
intercept about 5% more light than monocultures, therefore,
they may be more efficient in the capture and use of this
resource. In addition, peas may provide nitrogen benefits
to non-legume companion crops. Our results demonstrated that
both wheat and canola had significantly more nitrogen content
when intercropped with peas (Fig. 1), while the peas suffered
minimal losses in nitrogen due to this partnership. It is
likely that since peas were able to fix their own nitrogen
from the atmosphere, the wheat and canola were able to tap
into more soil nitrogen, the so-called 'sparing effect'.
is still too early to tell whether the northern 'three sisters'
will get along as famously as their southern cousins. One
thing is certain, however, farmers here on the prairies will
continue to ask the question, "How would I harvest all
those crops together?" The early Central Americans did
it by hand. This part of their elaborate system is unlikely
to imitated here, but the answer may be a machine such as
the 'McLeod Harvester', which is made right here on the prairies.