During April 28 to May 1, low temperatures were experienced across Kansas that can produce potential damage to recently planted corn. Cold temperatures can result in injury to the germinating seed as it is absorbing moisture. When soil temperatures remain at or below 50 degrees F after planting, the damage to germinating seed can be particularly severe.
A map for the duration of soil temperature at the 2-inch depth below 45 degrees F is presented in Figure 1. The main areas of concern are where soil temperatures were below 45 F for more than 8 to 10 hours, affecting all of western Kansas and parts of the north central region (very low temperatures were registered at Scandia). Note that for the western region, soil temperatures below 45 degrees F have an overall duration of at least 20 hours or more than 48 hours (Fig. 1).
Figure 1. Duration of soil temperatures below 45 degrees F at 2-inch soil depth for the period from April 28 to May 1, 2017.
Soil temperatures at the 4-inch depth during the first 24‐72 hours after seeding, when the kernels imbibe water and begin the germination process, are critical. Kernels naturally swell when hydrating. If the cell tissues of the kernel are too cold, they become less elastic and may rupture during the swelling process, resulting in “leaky” cells. Injury symptoms may include swollen kernels that fail to germinate or aborted growth of the radicle and/or coleoptile after germination has begun.
Soil temperatures below 45 degrees F at 4-inch soil depth were less widespread than at the 2-inch soil depth, but still affected large areas across the western part of the state with durations of more than 20 hours (Fig. 2).
Figure 2. Duration of soil temperatures below 45 degrees F at 4-inch soil depth for the period from April 28 to May 1, 2017.
Soil temperatures at 7 am May 1 are presented in Figure 3. The main concern for recently planted corn (planted in the last few days) is for the north central part of the state and all the western locations, where soil temperatures dropped below 40 degrees F, reaching a minimum of 34 degrees F at the 2-inch depth in the southwest region and 36 degrees F at the 4-inch soil depth. Note the low variation between temperatures at 2-inch and 4-inch soil depth.
Figure 3. Soil temperatures at 2-inch (upper value) and 4-inch (lower value) recorded at 7 am CT on May 1.
An open window for resuming corn planting seems likely to occur by early next week. If possible, wait and plant under more uniform soil temperature and moisture conditions to guarantee a more uniform early-season stand of plants.
More information about potential damage to recently planted corn will be more evident in the next week or 10 days. An update on planting status of summer row crops will be provided in upcoming issues of the Agronomy eUpdate. Stay tuned!
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Mary Knapp, Weather Data Library