Canola School: Preventing seed toxicity


Seed toxicity can severely impede canola yield, and it can be difficult to determine just how much nitrogen is needed in the seed row to see maximum results, while mitigating losses from possible seed toxicity.

On this episode of Canola School, Ken Wall, grow team advisor with Federated Co-operatives Ltd, breaks down seed toxicity and what to consider when determining ideal seed-row rates of nitrogen.

Canola seed tends to be more sensitive to nitrogen toxicity and is more susceptible to seed toxicity in general than other crops, such as cereals, which is why Wall says growers should take extra precautions when determining application rate and type. He says it’s important to take all factors into consideration when determine rates, including row spacing, openers and other drill options, soil type, and moisture conditions at seeding.

For this particular school episode, Wall references plots located just outside of Swift Current, Sask., a brown soil zone, which has less of a buffer against seed toxicity than a dark brown or black soil zone. The Saskatchewan Ministry of Agriculture has determined that 10 lb/ac, under normal circumstances, is the ideal rate for brown soil areas. That said, specific soil salinity of an area and lack of moisture create a situation where less is more.

“When we make those decisions in the spring, the recommendations are for normal conditions. When we have drought conditions, or in this case, there’s some salinity effects here. Those actually compound, or exacerbate, the problem. So the producers need to make that decision, are we gonna have a dry year? Are we dealing with some salinity? Are there other issues, which will determine the amount of fertilizer (in this case urea) that you will safely put with the seed?” says Wall.

In this particular scenario, the best emergence results were seen when the rate was cut in half to five lb/ac. Wall says it’s a good reminder that recommended rates should be just a jumping off point, not a set-in-stone rate.

The type of fertilizer applied has an impact as well.  “It depends what you’re putting down with the seed. In this case, we’re putting down urea. So in the guaranteed analysis of a real urea is 46 per cent, nitrogen, and no phos and no potassium. So not only do we have to worry about the toxicity, or the salt index of the fertilizer, in the case of urea, we also need to look at the byproduct of the bacterial breakdown of the real urea, which is ammonia. And that also has negative effects on seed emergence,” explains Wall.

As you move into areas with dark brown or black soil types, these areas are more forgiving and Wall explains why in the episode below.

To see the full library of Canola School episodes, click here.

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