I hope everyone’s 2021 planting season or fieldwork season has started off smooth. I wanted to reach out with a few things to consider this week with regards to planting corn. If you have noticed the 7-day forecast for this week (3/28 – 4/4), our Easter cold snap is right on time. Nighttime temperatures will be dropping in the low 30’s on Thursday and Friday nights with daily highs in the 50’s.
With this being said, the rain showers that were around today (3/28) and the rain that will continue through Wednesday (3/31) in various parts of the state, may have already put planting on hold. However, if planting does continue, I would use caution on planting significant acres in front of the cold period we will experience on Thursday and Friday. I would recommend delaying planting over Thursday and Friday until soil temperatures have increased to acceptable values following this weather event. Soil temperature is the component we are wanting to evaluate during this period. Clemson’s recommendation is to plant corn when soil temperature reaches a minimum of 50 degrees F at a 4-inch depth OR 55 degrees F at the 2-inch depth. Furthermore, when we plant, we want warm temperatures (>50+ degrees) in the days following planting to ensure we can generate enough heat units to get the seed to germinate and emerge quick and uniform.
If corn is planted, and soil temperatures get cold enough (< 50 degrees to freezing), several things can occur. Uneven emergence, growth, and development across the stand, issues with mesocotyl growth and reduced vigor can be noticed, leafing out underground, and severe cases can cause seed and seedling death.
Corn germinates in a two-step process where first, corn seed absorbs approximately 30% of its own weight in water and second, the growth of the radical and coleoptile occur. The second step is dependent on soil temperature and if soil temperatures are below 50 degrees F, then initiation and growth of the radical and coleoptile will not occur or will be very slow.
With slow growing conditions, seed will likely be exposed to insect and disease pressure for greater lengths of time, which could lead to further issues with emergence or seedling vigor. Planting into cold moist soils can also shock the seed when water is absorbed causing seed death and result in variable stands or total replants.
Last, we added soil temperature sensors to a weather station at Edisto REC. Feel free to use this information as you wish if it is helpful or beneficial. The link for the weather station is below. Sensors 1, 2, and 3 are at depths of 1″, 2″, and 3″, respectively. Column 1 is the real-time soil temperature, column 2 is the daily high temp, and column 3 is the daily low temp.