Shaun Casteel likes soybeans “green to the eye by the Fourth of July.” The Purdue University Extension soybean specialist uses this spinoff from corn being knee-high by the Fourth of July to emphasize that potential for high yields increases when row canopy closes and no sunlight hits bare ground by July 4.

The truth about 2019 is that there were likely as many soybeans still in the seed bag on July 4 as there were fields where canopies were completely closed. Many cornfields weren’t knee-high on Independence Day either, and most years modern corn is head-high or even tasseling by July 4. Not this year!

“Late planting impacts what we can expect during the rest of the season,” says Steve Gauck, a Beck’s sales agronomist based at Greensburg, Ind. Beck’s sponsors Soybean Watch ’19.

The Soybean Watch ’19 field was planted June 12. Two varieties were planted in the field: one with a full seed treatment plus Ilevo, and one only with Ilevo. Gauck’s stand counts put the variety without the  full seed treatment at 107,000 plants per acre, and the one with full treatment at 124,000 plants per acre.

“As long as we have 80,000 plants per acre, we figure we can achieve full yield potential,” he notes. Having extra plants helps since the planting date was late, however. Late-planted beans don’t tend to produce as many nodes per plant.

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What to watch for

Here are things Gauck will watch for the rest of the year. Some of this information can be found in the Purdue Corn and Soybean Field Guide, which Gauck carries in his back pocket.

Later critical weather dates. Soybeans begin flowering based largely on photoperiod, but maturity will still be somewhat delayed due to later planting. This means that instead of the critical period for reproduction falling in early to mid-August, it may be late August into early September, Gauck says. Sufficient moisture is needed for pod fill during that period.

Shorter reproductive period. Expect the overall reproductive period to be shorter, according to the Purdue guide. Flowering started before the canopy closed in some cases. It may have begun before July 4 for soybeans planted in early June, even if the canopy wasn’t fully closed.

Yield effect. Historical data indicates yield falls off quickly with delays in planting in June. The guide notes that you could still expect 92% of full yield if you planted by June 10, but only 82% if you were delayed to June 20 and 70% if you planted June 30. If you planted July 10, yield potential drops to 60%. Neither June 30 nor July 10 plantings are recommended, but many people had no choice this year. Some soybeans were replanted as late as July 15.

If growers increased seeding rates to get more total nodes per acre, they may have some chance of offsetting some of the expected drop in yield, Gauck notes.

Insects and diseases. Just because soybeans were planted late doesn’t mean you won’t see the usual disease and insect suspects this year, Gauck emphasizes. Green stinkbugs caused issues last year and are back this year. Continue scouting even as pods develop.

Even sudden death syndrome could appear. It was cool when many soybeans were planted, even though it was nearly mid-June, and that favors infection by SDS.