April 18, 2007
Most established alfalfa o.k. after cold snap
Don’t be in a hurry to give up on established alfalfa fields. Even though the top-growth has been killed and the alfalfa is taking a long time to re-grow, the crowns of most plants should still be fine. Re-growth should be more evident soon with these warmer temperatures. Even though air temperatures got down into the teens, the crowns are below ground where soil temperatures were warmer. It would likely take soil temperatures in the low 20s to kill the crowns. If there are fields where heaving had occurred over the winter exposing the crowns above ground, these plants could be in trouble. Steve Barnhart has a nice article on checking alfalfa for cold injury at http://www.agronext.iastate.edu/showitem.php?id=39. New seedings that had emerged will likely be killed, but fortunately there wasn’t much forage seeding done prior to the cold snap.
ANHYDROUS AMMONIA APPLICATION CONCERNS
There is a lot of anhydrous that will be going on in the next few days and weeks. A common question is “how long do I need to wait to till or plant after applying anhydrous?” As long the anhydrous is placed at the 6-8” depth and there is a good seal, there is no need to wait before planting. This is also true with tilling the soil as long as it is fairly shallow tillage. The most loss occurs if tillage is done right after application with a moldboard plow where the soil is totally inverted. Losses should be minimal with other tillage. If the anhydrous is applied at a more shallow depth or the zone that the gas spreads is greater (common with dry soils), applying the anhydrous at an angle to the corn row direction can minimize yield losses if there is a loss of stand due to fertilizer burn by assuring that an entire corn row is not injured. There is not a magic number of days to wait to avoid problems, but the longer the better.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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