Crop advisor casebook: What stalled Mark’s pea sprouts?

A Crop Advisor's Solution from the August 28, 2018 issue of Grainews

When we dug into the soil in the affected areas, we found pea seeds that had tried to sprout from one to five times (see 2nd photo further down). Healthy peas usually sprout only once. 
These shoots also looked like they’d been pinched off at the top.
Karly Treleaven. photo: Supplied

In the third week of May last year, I received a call from Mark, who farms 6,000 acres in the Forestburg, Alta., area. Mark was concerned about his pea crop after he discovered some areas in one of the two fields he seeded had no plants coming up. In addition to peas, Mark also grows lentils, canola, wheat and barley on his farm.

When I examined the affected field, I found randomly distributed bare patches in the seed rows surrounded by healthy-looking plants. There were no bare patches in the seed rows of the other field, and the plants were developing normally.

“Perhaps I seeded the peas too deep, and that’s why some of them aren’t coming out of the ground,” Mark said.

Seeding depth was just one of the factors we’d look at to diagnose the cause of the bare areas in the seed rows.

When we dug into the soil in the affected areas, we found seeds that had tried to sprout from one to five times — healthy peas usually sprout only once. These shoots also looked like they’d been pinched off at the top.

This pea seed tried to sprout five times! Not a sign that this was a healthy seed. photo: Supplied

That growing season, there was adequate soil moisture in the fields for germination. Mark had opted for a fungicide seed treatment on his pea seed and he had put down liquid inoculant.

Because Mark was worried he had seeded too deep, we dug up normally developing plants in the unaffected areas of both fields and compared them with the seeding depth of the shoots that hadn’t yet emerged in the bare patches of the affected field.

Both affected and unaffected plants/shoots were seeded at the same depth across both fields. Thus, seeding depth wasn’t the problem. We could also rule out seeder issues because the seeder settings were correct and the machinery was working properly.

Fertilizer toxicity wasn’t to blame either, as fertilizer was not placed in the seed row and seedbed utilization was high.

Pests were also on our list. We dug into the soil of the affected field for more than an hour looking for insects that could cause shoot damage; however, no cutworms or other such insects were found. Because there was a slim chance gophers could be eating the plants, we also looked for evidence of rodents. However, there were no gopher holes in this or surrounding fields.

What finally shed some light on the situation was a discussion Mark and I had about the seed’s origin. Two varieties were planted that spring, one in each field. Both varieties were harvested by Mark the previous fall and used for seed that spring. Now I had a hunch about the pea injury’s cause.

Crop Advisor’s Solution: Handle peas intended for seed sparingly

It was when Mark told me he’d planted two varieties, one in each field, from seed harvested the previous fall that I began to understand what was causing the bare patches in the one field.

In 2016, Mark planted two pea varieties. At harvest that year, one variety was combined at the correct seed moisture content, while the second variety was left too long in the field, and the seed moisture content was too low. As a result, those peas were too dry when harvested and some cracked when combined.

The injured peas were then further damaged when run through an auger that fall and the following spring. Thus, the seed was injured by mechanical damage. This type of damage causes the seeds to sprout multiple times. Healthy peas usually shoot only once. Eventually the strongest shoot of mechanically-damaged seeds survives.

The pea seeds that were mechanically damaged eventually came up, however, the plants were behind the rest of the crop with respect to maturity.

At harvest, Mark combined the peas at the correct seed moisture content and, afterwards, handled the peas sparingly.

There was no noticeable yield drag from the peas harvested from this field. The pea field seeded with the other variety also met Mark’s yield goal at harvest.

It’s important to be aware of the proper time to combine peas, especially on fields that are intended for seed use the following year. Additionally, handle peas to be used for seed as little as possible to decrease the occurrence of mechanical damage. The use of a conveyor belt rather than running the peas through an auger each time may reduce the incidence of injury.

Karly Treleaven works for Richardson Pioneer Ltd. in Forestburg, Alta.

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