Should it Stay or Should it Go

Jochum Wiersma, Extension small grains specialist

That's the question that was posed several times last week as it became evident that the green-up of winter wheat and rye fields was spotty. Determining how stands faired through the winter and are good enough to leave is the most difficult decision to make with winter cereals. The simple reason for this is that winterkill is rarely uniform across a field and adjacent plants do not all green up at the same pace.

Observations in the winter wheat, winter triticale, and winter rye trials in Becker and LeCenter confirmed that there is substantial winterkill in all three species this year. There is winterkill among the hybrid winter rye varieties in the trials - something not previously observed in Minnesota.

The recorded minimum temperatures during the cold outbreak of January 17 through 21st may have felt cold to us but were not extreme by any measure. The soil temperatures at the crown depth during that cold snap never dropped below 17°F and 20°F in Crookston and Becker, respectively. Those are not lethal temperatures for any of the three species. While the soil temperature briefly dropped as low as 5oF in Crookston a month later, soil temperatures in Becker never again dropped lower for the rest of the winter.

The minimum temperature is not the only environmental factor the crowns of the seedlings have to endure to get through a Minnesota winter. How well the crown can stay hydrated and keep access to oxygen plays a role as does avoiding tissue damage from heaving soil. It is impossible to say with absolute certainty, but desiccation of the crowns is likely the primary driver of the observed winterkill as the dry fall was followed by an open winter. Evidence that would corroborate this would be that winterkill is worse on tops of knolls or areas of the field with soil types that have less water-holding capacity. You may even find that seedlings in wheel racks fared better than those just adjacent to the wheel tracks.

The question remains ‘Should it Stay, or Should it Go’?

Winter cereals develop in the spring during relatively ideal conditions for tiller development. Therefore, the optimum plant stands can be less than their spring counterparts. A stand of 900,000 - 1,000,000 plants/acre or 21 - 23 plants/ft² will be enough to maximize grain yield. Research in North Dakota has shown that winter wheat stands of 17 plants/ft² can still produce near-maximum grain yields.

In the case of winter wheat, you can interseed spring wheat to fill large gaps but be prepared that harvest will be a bit more challenging as the spring wheat matures later than winter wheat. That is not an option for winter rye or winter triticale if the intent is to harvest the field for grain. Interseeding with oats, barley, and spring wheat can be an option if the field is diverted/repurposed for forage, however.