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Canola rivals barley in salt tolerance

It may come as a surprise to many growers, but canola is just as tolerant of salinity as barley, making it a viable option for moderately saline soils.


November 29, 2007
By Helen McMenamin

Topics

Salinity can limit your cropping options, but canola can be one of the better
options for salinity-affected land. Preliminary research shows some canolas
can grow and yield as well as barley under saline conditions.

The idea that canola might be more tolerant of salinity than was originally
expected first came to the attention of Jack Payne, as the agronomy instructor
at Olds College investigated problems in a hybrid canola seed field. Some areas
in the field were not growing well, but the male parent plants, seeded in strips
between the female parents, grew vigorously in problem areas.

 p18a
A saline area of a hybrid canola seed field showing extremely stunted
female parents beside male parents apparently unaffected by the soil conditions.
Photo Courtesy Of J C Payne.

Payne, a former salinity specialist, diagnosed the problem as salinity and
thought perhaps genetic variation allowed some plants to appear healthy while
others wilted in the saline patches. He enlisted the help of Harold Steppuhn,
leader of Agriculture and Agri-Food Canada's salinity laboratory at the Semi-arid
Prairie Agriculture Research Centre in Swift Current.

Steppuhn compared growth of three varieties of canola to Harrington barley
– the most salinity tolerant of several crops he tested some years ago.
Hyola 401 and an InVigor variety tolerated salinity better than others and better
than barley. Yields of those two varieties (see Figure 1) were not affected
by moderate salinity, EC 10 dS/m.

The salinity laboratory, one of only two or three in North America, is designed
to assess the impact of salinity on crops. It has a specialized hydroponic greenhouse
where each planting pot is automatically watered from its own nutrient tank.
Steppuhn can adjust the salinity of growing medium for each pot so he can isolate
the effect of salinity from other effects linked to salinity under field conditions.

Under these conditions, ideal in every respect except salinity, barley yields
dropped steadily as salinity increased. Canola was not affected by significant
salinity.

Conditions in saline areas change continually. Ground water rises, bringing
salts to the soil surface, then drops, leaving a salt solution in the surface
soil. Rainfall flushes salts back down through the soil profile. The salt laboratory
allows scientists to set salinity at a certain level and hold it steady throughout
their study.

After Steppuhn confirmed that some varieties of canola are more tolerant of
salinity than others, Payne seeded the same canolas in a saline area. Their
performance in the field matched the laboratory results.

Steppuhn has done preliminary tests on other canolas. Mustard and Polish canola
seem less tolerant than Argentine types, but he has not had funding for testing
to rank current varieties.

The varieties Steppuhn tested were the highest yielding varieties available
at the time, but have now been displaced by newer varieties.

"Salt tolerance is partly related to plant vigour," says Payne. "More
vigorous crops show more salt tolerance. That's the reason barley, especially
six row types, has been considered the most salt tolerant annual crop.

"It's also why the male lines in that hybrid seed field did so well in
the saline areas. Male parents of hybrids are generally more vigorous than the
female. Today's hybrid canola varieties are much more vigorous than early varieties
and are more competitive with weeds."

Consider your options
Kochia signals salinity problems because it is a strong competitor and does
well in saline areas. So it is an indicator that alternatives might be looked
at.

Although Payne considers hybrid canola a viable option for fields with low
to moderate salinity, he does not advise it for fields with serious problems.
"If you have white salt crusts, perennial forages are your only real option,"
he says. "No annual crops will thrive in that environment.

"Saline soil is a very harsh environment," he says. "Early in
the year, plants have to cope with wet feet and anaerobic conditions, since
salinity is related to poor drainage and waterlogged soil. Later, the salts
in the soil aggravate dry conditions by drawing moisture out of roots."

Perennial forages take advantage of early season moisture and their deep roots
and long growing season remove water from the soil profile. As a result, salinity
problems are reduced, but the salts will return with a switch to annual crops.

If perennial forages do not fit in the rotation, canola is an option for a
field where soil tests show an EC of 2 to 4, according to Payne. That sort of
salinity in a soil sample made up of 15 or more cores means some areas have
an EC of at least 6, moderately saline. Peas would have real problems in those
areas.

You cannot be sure which canola variety is the most salt tolerant, but Payne's
educated guess is the most vigorous hybrid, with a herbicide package to address
your weed spectrum is best. But good seeding practices are especially important,
he cautions.

"All the horsepower of a strong hybrid doesn't help if it's put into a
dry or lumpy seedbed or one that's not well packed. It's still a small seed
going into a very harsh environment. Seed on the right date, at the right depth
into a well managed seedbed with good weed control. This is not the place to
cut corners.

"Canola is no magic bullet for dealing with salinity. It's not going to
be a 70 bushel canola crop, but saline areas won't grow a bumper crop of barley
either. At the end of the day, compare your bottom line to your actual barley
yield, not its 100 bushel potential."

A break from barley also reduces root rots and foliar diseases that can drastically
cut barley yield over time. Canola is also a chance to use different weed control
tactics from those used in barley.

Although wheat provides a partial break from barley, all wheat cultivars show
greater salt sensitivity than barley. Steppuhn's work shows that Kyle durum
and Fielder soft white wheat are more tolerant of salinity than Katepwa hard
red spring or CPS wheats.