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Nitrogen strategies for durum

Growing high quality durum wheat is a goal with most growers, but the crop
can run out of nitrogen if not carefully managed. In research to determine how
to manage nutrients for optimum results, crop scientists have found that nitrogen
at seeding still provided the best yield and protein response – unless
environmental conditions changed. They also looked at the correlation between
fertility levels and fusarium infestations.

According to the researchers with Agriculture and Agri-Food Canada at Indian
Head, the data is still being tabulated, but it appears only the quality component
of the research was successful: managing fusarium needs further study.

In a three year test that was broken into the two components, William May and
his colleagues were unable to successfully manipulate the durum using nitrogen
or seeding rates to improve the canopy and reduce fusarium. However, they were
able to increase protein levels.

Nitrogen at seeding gives best combination of yield
and protein
"We found that adding nitrogen at seeding was the most effective way to
increase protein," May says. "If we top dressed at the five leaf,
flag leaf or flowering stages, we didn't get the same increases."

The research used four major varieties of durum wheat: AC Avonlea, AC Morse,
AC Navigator and Kyle. A base application of nitrogen to achieve 75 percent
of the soil test recommendations, which included the residual amount in the
soil, was made. Then, at the various stages, 20kg/ac, 40kg/ac and 60kg/ac of
nitrogen was top dressed onto the crop.

"We were trying to determine when the balance of yield and protein occurs,"
explains May. "Nine times out of 10 our yield improved when top dressing
occurred at seeding. Our best response to nitrogen in terms of protein occurred
at seeding as well. We did see improvements at other stages but the results
were inconsistent."

Consider top dressing if yield potential increases
in-season
The researchers also learned that in wet years protein can
always be improved once the yield is established. Since growers can get a premium
for protein, it pays to manage for protein improvement. Without nitrogen, quality
can be lowered and May says growers sometimes do not put enough nitrogen down
with the seed if the spring is warm and dry. That conservative approach can
be detrimental to quality, he cautions.

"If a grower is conservative with nitrogen application at the time of
seeding and then the growing season is wet, it would be wise to go back and
top dress some nitrogen," May advises. He suggests setting a yield target
and then fertilize accordingly. If the weather pattern changes, particularly
if there is rain, then growers should react because the yield potential increases.

An economic analysis of May's data will determine at what point the cost of
additional nitrogen is balanced or offers increased returns. While the attempts
to control fusarium fell short of the anticipated goals, the knowledge of how
to improve yield and quality, and balance both without harming one or the other
is invaluable. Growers aiming for those all-important premiums can hit their
target with judicious use of nitrogen at seeding and by top dressing when the
weather warrants it. -30-