May 18, 2016 Weekly Crop & Weather Update

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Below you will find the daily maximum and minimum air temperatures, 2-inch average and 25-year soil temps, growing degree units, and 24-hour precipitation amounts for this week. These values are recorded at 8 AM and reflect the conditions for the previous 24-hour period (8 AM to 8 AM) at the Southern Research & Outreach Center, Waseca.

Air Temp (oF) Growing Precip
Date Max Min Degree Units (inches)
Thursday, 5/12 58 45 4.0 0.24
Friday, 5/13 56 37 3.0 -
Saturday, 5/14 47 33 0.0 0.22
Sunday, 5/15 52 28 1.0 -
Monday, 5/16 66 32 8.0 -
Tuesday, 5/17 71 45 10.5 0.03
Wednesday, 5/18 65 38 7.5 -

Cold weather settled in Minnesota this week and brought an unwelcome frost to many of our corn and soybean fields. Temperature reached a low of 28 degrees on Sunday morning and hourly temperatures indicate we were below freezing for 5 hours. Most corn fields were nipped by frost. Temperature averaged 48.1 degrees. This is 10.3 degrees cooler than normal. Rainfall totaled 0.49 inch or 0.41 inch less than normal. Growing degree units (GDUs) totaled 34 which is about 50% of normal. Since May 1, we have now accumulated 137.5 GDUs. This is 17% less than normal.

Last year this week was slightly cool and wet. Temperature averaged 55.4 degrees and rainfall totaled 1.83 inches. Last year at this time we had accumulated 175.5 GDUs.

While young corn plants froze back to ground level the impact on stand and yield should be negligible since the growing point of corn remains below the ground until the 5 to 6 leaf stage. Soybeans are different and freezing back to the ground will likely cause the plant to die. Fortunately only a few soybeans that we had planted on April 11 froze and will not recover. Soybeans planted in the same area on April 27 were still below ground when it froze and are unharmed. Very few soybeans were planted in Minnesota by April 27 so frost should not impact soybean yields either. The weather since the frost has been good and we are already seeing corn resume growth and development. It is best to wait for corn and soybeans to recover from this cold spell before applying herbicide. By May 20, planting should have resumed normal growth and herbicide application could begin again. For more information on spraying corn and soybeans following this weather, read the following from Jeff Gunsolus, Minnesota Extension weed specialist: