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Boost the N and boost the fungicide?

Study shows oat growers should make separate decisions on how much of each to apply

With the increasing demand for oats in the food market, growers these days are paying attention to both yield and quality, leading to questions about managing both nitrogen and fungicides. Does use of one affect how much you should use of the other?

Not by much, according to research published this spring.

Agriculture Canada crop management agronomist Bill May led the study, which looked at the effects of fungicide application and N rates on oat yield and quality in Saskatchewan. The data was generated in 2012 and 2013, but May says the findings are still relevant and they suggest oat growers should manage fungicides and nitrogen applications separately.

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The goal is always to increase yield without compromising quality and test weight. Some producers have begun applying nitrogen in excess of 90 kilograms per hectare (80 lb./ac.), the authors note. At the same time, the use of fungicides has occasionally been connected with yield boosts even when disease-resistant cultivars are planted. If there isn’t enough disease to reduce yield, crown rust can contribute to lodging, so the idea is that using a fungicide such as strobilurin might bump yields in conjunction with N.

“We wanted to know if we have something that stands really well in an environment where there are rusts, what happens if we push the N rates?,” May says.

“What we found is that fungicides and nitrogen are managed separately — not together. Both can be effective but using a fungicide doesn’t mean you can use a higher N. When we looked at that, the optimum N rate we came up with was about 100 kg/h (90 lb./ac.), which was higher than we would have recommended from our previous studies — most of the others would recommend 60 kg/h (54 lb./ac.).”

The experiment was set up as a split plot with fungicide (none, pyraclostrobin, propiconazole and trifloxystrobin) in the main plot, and eight N rates in sub-plots (5, 20, 40, 60, 80, 100, 120 and 140 kg/ha).

Grain yield increased along with the N rate, with a corresponding decrease in test weight. The researchers found that an N rate of 100 kg/h (90 lb./ac.)provided the most consistent economic returns when crop prices are between $162 and $194/tonne ($2.50 to $3 per bushel).

But no interaction between fungicide and N was observed.

Regional decisions

May’s past research has shown little benefit to applying fungicide as a preventive, although this is a trend he’s seeing in Prairie oat production.

A study he published in 2014 showed that when even a moderately resistant cultivar was planted early enough in the season, there was little to no benefit to spraying a fungicide in rust-prone areas of eastern Saskatchewan.

Alan Butuk, chair of the Saskatchewan Oat Development Commission (SaskOats), says decisions about fungicide applications vary by region, but the trend in some areas of eastern Saskatchewan is to apply fungicides preventively, even if crown rust-resistant cultivars are planted. “We find it helps with standability and bushel weight,” he says. “The years we don’t do it, we tend to have more of an issue.”

When it comes to nitrogen rates, Butuk says they also vary by region.

“North of Edmonton, they have a foot of topsoil, and down here there’s only a few inches. The N rates are very different. Most producers will operate in that 50 to 75 pounds per acre range. If you put too much you have the potential for lodging. But there are problems on the other side if you go too low.

“It’s producer-to-producer,” he says. “If we go back a few decades oats was a filler crop and now the oat growers are looking to fine-tune their crops to get that last 10 per cent of profitability.”

Seeding date key

May says that seeding date and cultivar selection have the biggest influence on grain quality.

“If you’re using cultivars with decent crown rust resistance and early seeding, you really don’t need a fungicide,” he says. Past May 15, some producers will start to see issues with test weight, particularly in the southern and western parts of the province. Later into May, those impacts catch up with producers in eastern Saskatchewan.

“Make sure the crop is uniform — 300 plants per square metre,” he says. “Put down phosphorus in a side band to help oats compete with wild oats. P will help the most when combined with a high seeding rate.”

When it comes to N rates, producers should err on the side of caution and stick to the recommended 55 lb./ ac. to start with until they gain a stronger sense of crop performance in their area, he says.

“Growers need to look at their overall agronomic practices and start with an N rate that won’t blow the barn doors out on yield but will ensure a high-quality crop. They should have a pretty good idea of how high they can go before test weights come down.

“In general, my recommendation is to start more cautiously with N and only get more aggressive as they get more familiar with their test weights. 60 pounds, 70 pounds will do the job 95 per cent of the time.”

About the author

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Julienne Isaacs

Julienne Isaacs is a Winnipeg-based freelance writer and editor. Contact her at [email protected]

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