Medford Cooperative

Temperatures will be dipping low tonight and frost will likely be something to consider. If you are wondering what impact that might have on your crops, this guide from West Central should help:

CORN

Germination:  Cold soil temperatures (sub 50o F) can trigger imbibitional chilling injury or cold temperature injury.  These phenomena occur when either seed kernels imbibe water that is colder than what is considered ideal resulting in ruptured tissue during cell expansion or from damage to the mesocotyl during cell elongation.  Plant death is possible but more commonly observed are corkscrewed mesocotyls that are responsible for arrested development or delayed emergence.

Emergence to V5: Very little effect, even if crops are completely defoliated, as the growing point is still about one-half inch below the soil surface. New growth should be visible the day after frost as long as the temperature rises above 65 degrees F. Stands can be evaluated after a few days to determine whether certain plants will survive.

V6 or later: Growing point is now above ground. Lodged plants can recover and continue to grow, but plants snapped off at the base are dead. Plants that were borderline 5-6 leaf should be monitored for three or four days to see if regrowth occurs. Stem bruising can be a problem that manifests later in the season. Young stalks will be able to stand with bruising, but, if significant, plants in later stages may not be able to support their own weight and will be more prone to lodging.

SOYBEANS AND DRY BEANS

Seed Germination: Soybean will readily germinate at soil temperatures near 50o F. However, the concern relating to soybean that germinate in cold soils is that the germination processes are dramatically repressed thus maintaining the seedling at a susceptible stage for a longer period of time for injury from seedling rot pathogens to occur. Dry bean are not as tolerant to cold or frost as soybean and generally require planting at or near the last frost free date for a given geography.

Cotyledon: Soybeans can survive temperatures down to around 27 degrees F for several hours.

Unifoliate to Trifoliate Stages:  Soybean at these stages are more sensitive to frost than when in the cotyledon stage. However, plants can compensate readily for frost or hail damage even when the terminal bud is destroyed because soybean are capable of growing from axillary buds. However, if the plant is cut off below the cotyledons of the plant, the plant will not regrow and, like corn, soybean stem bruising from hail can cause plants to be more prone to lodging at later stages.

Always wait a few days after injury before assessing bean stands for replant decisions.  Soybean plants may take up to 4 to 7 days after injury before regrowth becomes evident. The general rule of thumb is that if 4 plants per foot of row remain, the crop can still produce appreciable yields.

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