I have stressed more often than not that in Minnesota you ought to seed your small grains as early as possible. The very late starts in the past two years and the disappointing wheat and barley yields that followed in especially the southern half of the state are a testament to my position on planting dates.
I try to practice what I preach and so I seeded trials last Thursday and Friday near Rochester, New Ulm, LeCenter, and Becker. I was happy to see that some of you were also seeding your first small grains. And then it snowed again and the thermometer will be stuck near or below the freezing point much of this week. Should you and I be worried about these early seeded small grains?
Spring wheat (and spring barley and oats) will start germinating in earnest when soil temperatures reach 36⁰F to 40⁰F. Once the imbibition phase starts there is no return to dormancy and the germination/emergence should be as quick as possible to establish a healthy, vigorous seedling. Protracted emergence will predispose the seeding to attacks of soil-borne fungi like Pythium damping-off or common root rot, ultimately reducing stands. During this whole germination and seedling emergence and up to the 5-leaf stage, the growing point will be at ~1-inch depth. At this depth, it is protected from the ambient temperatures. The crown can sustain temperatures down to 28⁰F and probably even handle short periods of temperatures as low as 22⁰F. Even if above ground leaves freezes, the plant will survive and continue its development as long as the crown does not suffer any freezing injury.
The seed is most prone to freezing during the imbibition phase as the cells have not started actively growing and dividing yet. With air temperatures expected to drop down into the high teens overnight, I have fielded a number of calls already this morning with the question whether the earlier seeded wheat, barley, oats (or any crop for that matter) will make it.
Know that the blanket of snow you received over the weekend will help insulate the seed from the predicted lows. This morning the recorded minimum temperatures at 2” soil depth at the SWROC and the SROC in Lamberton and Waseca were 35⁰F and 36⁰F, respectively. The soil temperatures will likely not drop below 28⁰F in the next few mornings and before the weather is forecasted to warm up later this week.
The fastest way to tell whether the seed is still viable is to dig up some seed or seedlings and place them on a wetted down paper towel at room temperature. Within 24 hours you should see elongation of the coleoptile or radicle of the seedling. With seed that had not germinated yet, you may have to wait a few days before you see a radicle and coleoptile appear. If the seed and the germ are damaged by frost they will turn to mush within 24 hours at room temperature.
Source : umn.edu