Seeding is about time, temperature

FARGO, N.D. -- Farmers are getting into the fields later than normal this year, so have to make decisions on seeding rates and varieties.

Joel Ransom, a North Dakota State University extension agronomist, says, the planting date alone is not the only influence on yield. Drought and other conditions can play a role.

“In most seasons, planting on or before the recommended optimum date will enable higher yield potential than when planting later,” he said in the April 30 “Crop and Pest Report.”

Planting small grains early in the season is typically good because “cool season” crops can grow earlier in the season that favor their development.

Research shows there is a “recommended optimal date” for most small grains. That ranges from the second week of April in southern North Dakota, to the first week in May in the north.

Ransom says there is a 1% reduction in expected yield after that date.

Similarly, Ransom offers charts for the “last planting date” for small grains ranging from the second week of May in the south to the first week of June in the north.

Ransom recommends calculating “seed numbers per acre” and not bushels per acre, because that can vary by seed weights.

Significantly, recommendations are based on “live” seeds so must be adjusted if low germination. Typically, of the live seeds, 15% of seeds in plots don’t produce viable seedlings.)

Ransom suggests farmers:

* Use seed tags to get the number of seeds per pound. (Alternatively, farmers also can count 1,000 seeds, weighing them with a kitchen balance, and doing the math.)

* Start with a “base seeding rate” of 1.5 million seeds per acre for spring wheat.

* Cut wheat seeding rates by 100,000 seeds per acre when expecting yields less than 50 bushels per acre.

* Cut the seeding rate by 200,000 seeds per acre for varieties rated “5” or higher for straw strength.

* Increase the seeding rate from the base rate by 100,000 seeds per acre when expecting yields higher than 50 bushels per acre, and when using a variety with good straw strength that produces fewer tillers.

Corn planting progress also is a bit behind normal, Ransom says.

The “optimal period” for corn in North Dakota is the first two weeks of May. In the past decade only about 50% of the corn is planted by May 15, in most years.

In 2019, Ransom and NDSU on May 20 recommended switching to early-maturing hybrids because only 50% of the corn had been planted as of May 15.

“Last year illustrated the risks of staying with a full season hybrid when planting is delayed, as many of the late-planted full season hybrids did not reach maturity before the end of the season, resulting in low test weights and very wet corn.”

Corn is a warm season crop and doesn’t grow at temperatures less than 50 degrees.

Planting corn in early May can fall victim to “imbibitional chilling injury.” That’s when the seed the seed “imbibes” (absorbs) water that is less than 50 degrees, from soils that don’t warm for the first 24 to 36 hours after planting, or if there is a cold rain or snow shortly after planting. Other factors like management and weather determine ultimate yield.