As soil temperatures have heated up throughout April, producers in the Southwind District have been hard at work planting corn and early soybeans. This past week, we experienced unusually cold, and even freezing temperatures, leaving producers wondering how this could affect any planted corn and beans.

Corn

Cold temperatures can result in injury to the germinating seed as it is absorbing moisture – a problem called imbibitional chilling injury. Germinating seeds can be damaged when soil temperatures remain at or below 50 degrees F after planting.

Soil temperatures at the 4-inch depth during the first 24-72 hours after planting are critical. It is during this window that the kernels imbibe water and begin the germination process. Kernels naturally swell when hydrating – taking in water. 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.

Chilling injury can also occur following germination as the seedlings enter the emergence process. Chilling injury to seedlings can result in:

• Reduced plant metabolism and vigor, potentially causing stunting or death of the seminal roots
• Deformed elongation (“corkscrewing”) of the mesocotyl
• Leaf burn
• Delayed or complete failure of emergence, often leafing out underground

Chilled seedlings may also be more sensitive to herbicides and seedling blights.

Soybeans

For this crop, a similar impact could be expected but depending on the planting time and overall plant growth. The most susceptible stage is as the plants are emerging (recently planted). The most typical sign of the impact of freezing temperatures on soybeans can be visualized in the stem and mainly with the yellowing of the cotyledons. If soybeans were advanced in growth, with unifoliate, then the overall impact of a freeze on the cotyledons will be very minor, with most likely no yield loss. If there is a large impact on cotyledons (without having unifoliate leaves unfolded), then there is a lower chance for those soybeans plants to survive.

For some of the fields scouted in the last days, most of the damage is cosmetic and even when some yellowing was present in cotyledons, this effect is minor and most likely will not produce any impact on yields.

Producers should consider all these factors when deciding on the planting time. Before making any decisions, fields should be scouted 4-7 days after the cold occurred as the extent of the damage and potential for new growth will be evident during this time.

If you suspect your crop may be showing symptoms of freeze injuries, it is important to contact your insurance agent prior to making any management decisions. For more information on freeze damaged crops, contact Chad Guthrie, crop production and forage management agent, at any Southwind Extension District office.