Soil Temps in Soybeans – John Viertel

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Soil Temps in Soybeans – John Viertel

On Saturday, July 20, 2019, I put my Soil Thermometer in the pickup, and I was on a mission to check the soil temps in a couple fields of no till soybeans. First, this at 11 a.m. and I took the readings at a depth of about 3.5 to 4 inches. The air temperature on my truck was 90 degrees. This was a field of beans did not have a cover crop. The picture on the left, showing a temp of 80 degrees, was bare ground in a sprayer track. The picture on the right at 72 degrees, was in the middle of the 15-inch rows, under the canopy. Notice how well shaded the ground is. Plant height, just over knee high.

I then went to the field that we had rolled down the cereal rye and then no tilled the soybeans. Temperature readings were again 3.5 to 4 inches. The air temp had gone to 91 degrees on the truck. I was really expecting lower temperatures, but they were very similar. In the sprayer track, 79 degrees. Between the 15-inch rows, 75 degrees. Bean height, just above my knees, but the canopy was not shading the middles as well. Found out the two fields had been planted to different varieties of soybeans. The ones in the rolled rye did not close the canopy as quickly as the no till field.

What did I take away from this? Because the optimum soil temperature for active metabolism in most plants’ root zones is 64 degrees, striving to keep the soil temperature down is vital to having a plant that is not stressed, is able to take up moisture and nutrients more efficiently. Both the straw mulch from the rolled cereal rye and shade from the closed canopy help keep the soil cooler at the depth the temperatures were taken. The straw mulch will do the job until shading from canopy can take over.  I think I will pick a hot day this month (August) and do this again.

If you remember, that was the week that we had some very hot, humid conditions in Central Missouri. The Sunday night and early Monday morning following me being at those fields, they received about 2.5 inches of rain. Very welcomed!

John Viertel