Crop advisor casebook: Spotty canola emergence baffling

A Crop Advisor's Solution from the October 15, 2019 issue of Grainews

All of Fred’s canola seed was planted at a consistent three-quarter inch depth, so why the uneven emergence?
Gene Enderson. photo: Supplied

I received a call from Fred last May after he came across a problem while out scouting his canola fields. He’d observed some spotty emergence of canola seedlings in one of his fields and was wondering why emergence was so much better in the adjacent fields that had been planted around the same time.

Fred, who also grows wheat, barley, peas and canary seed on his 6,500-acre farm in Mistatim, Sask., said he thought that poor seed quality, improper seeding methods or fertilizer burn might be to blame but he wasn’t sure.

I went out to Fred’s farm to have a look for myself. When I surveyed the problem field, I could see the canola seedlings that had emerged were distributed unevenly across the field. A closer look at the seedlings revealed that they were healthy with well-developed roots.

Since cutworms had been prevalent in several nearby fields, I checked the canola plants for cutworm damage. Not only did I not find any cutworms or damaged plants, but the pattern of the seedling emergence was too random to be caused by feeding cutworms. I also couldn’t find any signs of flea beetle damage.

Fred informed me it had been a fairly dry spring but pointed out that almost 19 inches of rain had fallen the year before; this was about the average for the area. When I examined the clay loam soil in Fred’s field, I could see the top half-inch was dry, but the planted seeds were sitting in moist soil and there appeared to be an adequate supply of subsoil moisture below them.

All of the canola seed was planted at a consistent three-quarter inch depth. When I asked Fred about the seed, he told me that he used the same variety and seed lot across all of the canola fields on his farm. When I checked with other canola producers in the region who had used the same seed lot as Fred, none of them reported any quality or emergence issues.

I inquired about Fred’s fertility practices and he explained that he used a seed-placed blend of ESN and MicroEssentials S15. All of the seed-placed fertilizer was applied two weeks prior to my scouting the field with Fred, and his seeding implement had a seed bed utilization of 10 per cent. Fred also informed me that on parts of the field where there was a water run, he had increased the fertilizer rate and adjusted the fan airspeed control on his equipment to its highest setting in an effort to put down a desired higher rate of product.

When examining the soil earlier, I’d found some canola seeds with damaged seed coats and a few ESN prills that had damaged polymer coatings. I wondered if this had anything to do with what was going on in Fred’s field.

Crop Advisor’s Solution: Mechanical damage while planting caused spotty canola emergence

After ruling out insects, insufficient soil moisture and improper seeding depth, I found my answer when I dug up some soil and observed some canola seed with seed coat damage alongside damaged ESN prills from Fred’s seed-placed fertilizer blend.

It turned out while planting Fred had increased both the fertilizer application rate and the fan’s airspeed on his equipment in order to maximize production on the parts of the field that crossed through a water run.

These areas also corresponded with the parts of the field with spotty canola emergence, so I now had a clear picture of what must have happened. The higher fertilizer application rate and increased fan airspeed caused some mechanical damage to both the canola seed and the ESN fertilizer as it passed through the system. The damage on the ESN prills resulted in an increased release rate of nitrogen fertilizer than expected. This, in turn, caused fertilizer burn on the canola seed which prevented germination.

Fortunately for Fred, the plant stand reduction was not high enough to significantly reduce the yield in the field and he was happy with the crop at the end of the season.

In order to keep this kind of mechanical injury from happening again, Fred will avoid increasing the fan airspeed setting and he will be more cautious when deciding how much seed-placed fertilizer is acceptable for his operation.

Gene Enderson works for Richardson Pioneer Ltd. in Crooked River, Sask.

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