Fertility and Nutrients
Feeding your oats
By Rosalie I. Tennison
There is a resurgence of interest in growing high yielding, high quality oats.
When horses were the engines of farming, growing oats was the renewable resource
that fueled them. As the number of horses in the country declined, so did the
number of acres seeded to oats, and interest and research turned to improving
other crops, such as canola. Now, the health benefits of oats are driving a
renewed interest in managing the crop for yield, quality and profit, and in
sufficient quantity to meet the increased demand.
Research at Agriculture and Agri-Food Canada in Brandon has examined the impact
of fertilization on growth and yield and quality of the crop. Dr. Ramona Mohr
conducted a three year trial at two sites to determine when fertilization is
"We didn't examine quality specifically, but we did find nitrogen does
have a role to play in quality," Mohr explains. "Nitrogen did influence
the quality parameters we measured, such as test weight, kernel plumpness and
kernel size, but typically we saw small declines in quality with increasing
rates of nitrogen. We were looking for how nitrogen, phosphorus and potassium
chloride can affect oats yield and quality."
The research included 24 treatments plus a control plot to determine which
rate fertilizer had a definite result on yield, and which rate and combination
of N, P and KCl optimized yield and quality.
"We saw that yield was optimized, on average, when 100kg/ha of nitrogen
was available to the crop," says Mohr. She explains that the 100kg includes
the amount of nitrate-nitrogen, at a 60cm sampling depth that was available
in the soil at time of seeding.
"We were unable to define a recommendation on the amounts of phosphorus
or potassium chloride that was needed to affect yield in the plant," Mohr
In fact, her research determined that phosphorus does not have an effect on
quality in particular. At two of six sites, phosphorus application increased
grain yield, but did not have a consistent effect on grain quality. In the case
of potassium chloride, there was a small, but statistically significant increase
in grain yield at one of six sites, even though all sites contained what would
be considered medium to adequate levels of potassium in the soil.
The observed crop response to fertilizer phosphorus application did not appear
to be closely linked to soil test phosphorus levels. The response to phosphorus
addition in 2002 may reflect the very dry, spring soil-moisture conditions,
reducing the availability of soil phosphorus to plants and contributing to the
positive crop responses to fertilizer phosphorus.
While the research was not focussed solely on quality, the aspects of quality
that were tested allowed the researchers to determine if certain rates of fertilizer
may play a role on quality.
Potassium chloride had a small effect on quality, but not significant enough
to warrant specific recommendations based on its application under the conditions
of this research, Mohr explains.
N rates that are just right
In the end, Mohr's research determined only a recommendation for
nitrogen in the 100kg/ha range. She cautions against applying excess rates of
nitrogen fertilizer to oats because a negative effect on quality can result,
in addition to lodging and loss of harvestability.
"A soil test is always the starting point," Mohr reminds growers.
"You also need to rely on your experience in your own field. For example,
in a field with a history of manure application or alfalfa production, nitrogen
may become available to the plant as the growing season progresses. A soil test
will help you determine the level of nutrients in the soil at the time of sampling,
and soil test recommendations will provide a general guideline for fertilizer
application, and then you can make adjustments for your own experience and knowledge
of your fields."
More research is needed to set rate recommendations for phosphorus and potassium
chloride and to determine how these nutrients influence quality. Phosphorus
did enhance early-season growth and increased yield at one-third of the sites,
but effects on quality were inconsistent.
With potassium chloride, only small improvements in grain yield and quality
resulted. As well, application of potassium chloride on soils with adequate
levels of potash did not usually provide an economic benefit in this study.
Mohr says oat research is in the 'catch-up' stage because it was abandoned
as the number of acres seeded to the crop declined. However, with renewed interest
in oats, research for it has been on the upswing. There have been several studies
in Manitoba to assess nitrogen fertilization in oats that contributed to new
provincial soil test nitrogen recommendations for oats in that province, but
there is still work to be done.
Plant and soil scientists have to expand on Mohr's initial research before
definitive recommendations on application of all nutrients can be made. Improving
both yield and quality of oats is possible when growers have the information
they need to produce this 'renewed' crop successfully. -30-