How to figure seeding rate

Each year questions arise about the correct seeding rate for hard red spring wheat, says Jochum Wiersma, University of Minnesota Extension small-grains specialist.

“Is a bushel and a peck enough?” is a question that he’s been asked more than once, he says.

Research in the mid-1990s demonstrated that — on average — an initial stand of 30 to 32 plants per square foot maximized grain yield, Wiersma says.

As planting was delayed past the optimum, the initial stand needed to be increased by approximately 1 plant per square foot for each week of delay to maximize grain yield.

“With this number in mind, and assuming a stand loss between 10% and 15%, one can calculate a seeding rate with the following formula,” Wiersma says:

Seeding rate = (desired stand) x (1 – expected stand loss) / (seed count x germination rate)

However, research also indicates that optimum seeding rates differ for individual varieties.

Some good data is available on older varieties, but it’s been impractical to test different planting rates as new varieties are released. However, you can estimate optimum seeding rates for new varieties based on what was learned in previous studies, Wiersma says.

Varieties that tillered well tended to have lower optimum plant densities when planted early, while varieties that didn’t tiller as much required higher plant densities for both early- and late-planted seeds.

“Therefore, if you’re growing some varieties that tiller well — such as Faller — you can probably be near the lower limits of the current recommendation, while varieties that do not produce as many tillers — such as Granite or Vantage — should probably be seeded at, if not beyond, the current upper limits of the recommendations,” Wiersma says.

Smart N may boost protein

Environmental Smartnitrogen shows some potential in boosting wheat protein levels, says Dan Kaiser, a University of Minnesota Extension soils specialist. He spoke at the recent International Crop Expo in Grand Forks.

ESN is a new coated urea product. The coating is supposed to slow down the release of nitrogen. In theory you could apply this is the spring, and N would be released later in the year, in time to boost protein levels. But in practice, the release is inconsistent. The warmer and wetter the soil, the faster the coating breaks down. Also, the coating can be cracked or thinned out during handling. In cool and dry weather, it may break down more slowly than expected. The N may be tied up too long to maximize yield.

If you use ESN, Kaiser recommends at least a 50-50 ESN/standard urea mixture. A 25-75 mixture might be even better, he says.

This article published in the March, 2010 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.