In wetter, hotter areas of the prairies, left-over heat, sunshine and rainfall could be put to good use.
November 15, 2007 By Bruce Barker
Not all parts of the prairies are in the enviable position of having a long
growing season with good moisture. Yet even in those areas that do, those resources
can be wasted if the field is left sitting after harvest. Martin Entz, a professor
at the University of Manitoba's Plant Science Department, says farmers in other
parts of North America put those resources to work and prairie farmers could
"In some ways, western farmers are starting to use some of those systems,
like using winter wheat or long season crops such as corn and soybean, but there
is still an opportunity for farmers to use more of the left-over resource,"
For example, he says that in southern Manitoba, wheat requires 1200 growing
degree-days to mature, yet from April to October, it receives about 1600 growing
degree-days. "In many years, the amount of left-over growing degree-days
can be greater than 400 and sometimes gets close to one-half the required amount
to grow a barley crop," says Entz.
Using surplus resources
In some of the semi-arid areas of the prairies, there may not be enough moisture
to take advantage of the left-over growing degree-days. In those areas, the
moisture is better saved for the following crop. But in areas where moisture
is not limiting and where excess moisture can be a problem, Entz says there
are a few different cropping strategies that can be used to take advantage of
the surplus resources.
Growing winter cereals is one practice that is taking off in Manitoba. Entz
says winter cereals take advantage of fall heat and moisture and also present
opportunities the following year with relay cropping.
Relay cropping involves seeding one crop before the first crop has been harvested.
A common practice in Ontario is to seed red clover into a growing winter wheat
crop in the spring of the year. After the wheat is harvested in the summer,
the clover is left to grow and can be used as a late season nitrogen fixer.
The crop can be disced down as a green manure crop in the fall or harvested
A twist on the clover relay seeding in drier areas could be to use precision
farming techniques to seed clover only in the low spots which are prone to excess
water. The clover could harvest the water, so that the potholes are not full
at seeding. It could also contribute to high fertility in those areas that usually
produce the most grain yield.
Entz says that another way to utilize the resources left-over after a winter
wheat crop is to seed a green manure crop immediately after the winter wheat
harvest. He says trials in Manitoba showed that above-ground dry matter production
after 48 days of fall growth was 1000lb/ac for chickling vetch (AC Greenfix),
980lb/ac of Indian Head lentil, 660 pounds for Berseem clover and 1230 pounds
for Nitro alfalfa. As a green manure crop, they would all provide significant
N benefits the following year.
Intercropping is another way to take advantage of extra resources. Entz says
the best is sowing winter and spring cereals together in the spring. The spring
crop, barley for example, can be taken off as silage, leaving the winter crop
to regrow throughout the fall. Winter triticale or fall rye both work well as
late season forages in this system. They are then terminated late in the fall,
freeing up the field for another crop in the following spring.
"Some farmers are using this double cropping strategy and from what I
understand, the ones who try it like the system," says Entz. He gives credit
to researcher Vern Baron at Agriculture and Agri-Food Canada at Lacombe, Alberta
for developing this system.
Adding annual or perennial forages into the crop rotation is also effective
in harnessing more of the natural resources. These crops grow late into the
year and bring many advantages including herbicide resistant weed management,
nitrogen and soil structure improvements and a break in the disease cycle.
One long-term project that Entz is conducting with funding from the Western
Grains Research Foundation is the use of annual medic as a self-seeding cover
crop. As a legume, it has the potential to provide nitrogen benefits. With self-seeding
varieties, the regular spring annual crop could be grown and after harvest the
annual medic would take over, fixing nitrogen and putting the surplus resources
to good use.
"Australian farmers use annual medic as a cover crop to protect the soil.
If we could develop a similar system, it would be a twist on relay cropping,"
Advantages add up to better efficiency
the main advantage of diversifying the cropping system is using some of those
'free' cropping resources. And if they are not used, there are hidden costs.
The land is a capital cost or comes with an annual rental cost. By using all
of the natural resources, these costs can be spread out over greater productivity.
"You pay taxes on your land based on its productivity until the end of
October, so why not put that land base to work?" asks Entz.
Another key advantage is moisture management in areas that are susceptible
to spring flooding or excess water. Drying out the soil in the fall can make
it easier to get out onto the land earlier in the spring. Salinity control can
also be improved by using up water in recharge areas. Drying out the recharge
areas can help to slow the movement of salts into the soil rooting zone.
Not every farm on the prairies has surplus water and heat. In fact, over the
last few years, water has been in short supply in many areas. But for those
farmers who usually have excess moisture, adding diversity to the cropping system
can add further efficiencies to the land resource and produce better cropping