Soil Temperature and Successful Planting of Sorghum, Corn, & Cotton
Planting season is upon us, and many good producers are getting very antsy about getting into the field, especially our sorghum producers who need to get that crop started and get as much development completed as possible before the dreaded sugarcane aphid arrives. This morning I took a soil temperature reading 1 mile east of Cotton Center, Texas in southwestern Hale County. It was at 60°F and in no-till with heavy corn stubble cover. This is a pretty good soil temperature for planting corn or grain sorghum, but is far too cool for cotton.
The minimum soil temperature for corn is 56°F (preferably 58°F or with a warmer week ahead to emerge into) while sorghum requires a 58°F (preferably 60°F or with a warmer week ahead to emerge into). However, most of the weather forecasts I can accumulate are calling for some moderately cooler temperatures later in the week and into early next week. With those ‘moderately’ cooler temperatures likely not dropping the soil temperatures too much, I feel pretty good about getting a big chunk of our corn and sorghum planting done this week, especially if those ‘cooler days’ come with the predicted chance of rain they are predicted to be with. On the other hand, we likely need to ignore the calendar date for a week or so longer this spring for our cotton planting needs.
Cotton gets off to its best start when planted in a recommended 69°F consistent temperature soil (roughly 64°F bare minimum with high air temperatures in the upper 80’s to low 90’s for the following week to continue a steep soil warming trend). Soil temperature can and does generally follow air temperatures with some lag time. Higher moisture content in the soil usually slows the soil’s response to air temperatures while dryer soils respond quicker. Likewise, soils with heavy cover will naturally be cooler through the shading of the soil by the cover. The best time to take soil temperature reading in your fields would be between 7 AM and 10 AM. That early morning period is when the soil temperature should be at its lowest, guaranteeing that the reading is accurately the minimum temperature we need to be watching.
Good luck and good planting!