Frost Damage
Vintage: 9 June 1998
The spring of 1998 was highly unusual in that unseasonably warm conditions allowed producers to plant early. The plants, once established grew rapidly and by late May or early June had reached the 9 leaf stage in some cases.
The problem arose when in early June, several nights of cold and sometimes freezing conditions hit these corn seedlings. A high degree of variability in frost damage could be seen in farmer's fields. Some fields were damaged while others were untouched. Yet other fields showed some areas of damage. On the whole, most fields showed some degree of damage.
Symptoms of frost damage
- Leaf tip burn- most often seen on the youngest leaves (top leaves)
- Darkening of leaves - the field will take on a black appearance probably due to the destruction of cell membranes by ice crystals formed in the cells.
- Plants may turn brown a day after the frost, although a closer look may reveal that the lower part of the plant (i.e., the pseudo stem) is still green.
Frost damage is more likely to occur in:
- Fields with lighter soils - lighter soils dry faster; dry top soil insulates soil below it thereby preventing warming of the air above the soil surface by soil radiation.
- Fields that have been recently cultivated or had anhydrous ammonia applied - same explanation as above.
- Low-lying areas - cold air settles in low-lying areas because cold air has a higher density than warm air.
- Reduced tillage - substantial amounts of residue can function as a blanket that prevents soil radiation from heating air immediately above the soil surface (Note: the amount of residue in no-till systems could be sustantial after corn and relatively small after soybean). On the other hand, reduced tillage will increase soil moisture (resulting in higher heat capacity of the soil) and firming the soil (resulting in increasing its conductance of heat). The particular combination of residue quantity, soil moisture, and soil structure will determine whether frost damage is more or less likely to occur in corn.
- Areas in which weeds were growing - the same explanation as for residue coverage.
- Areas of the field close to the edge - grass functions as a blanket preventing the warm soil to heat the air above it. Edge effect will be larger depending on prevailing wind direction during time of frost.
- Corn that has recently been sprayed with herbicide - herbicide stress on corn is compounded by the cold stress.
Will the corn recover?
- Stage of development less than 5 leaf tips - the growing point will usually be below the soil surface until the 5 leaf (tip) stage and soil temperature does not usually decline below freezing; effect of freezing air temperatures on corn with less than 5 leaf tips will be minimal (Fig. 1).
- Stage of development more than 5 leaf tips -
- a) If only the leaves are damaged but the whorl appears healthy (Fig. 2) plants will recover fully. In this case, both symptoms and yield effects are similar to herbicide damage as seen for example with Pardner.
- b) If the lower half to two-third of the corn plants are not damaged by frost (Fig. 3), they will likely survive. However, the subsequent leaves will emerge onion-leaved due to their attempts to break through the dead tissue of the upper whorl. Under those circumstances, the dead part of the whorl can be cut off with a rotary chopper to allow leaves to emerge normally. Maturity will be delayed and yield will be lower even if this treatment is successful.
- c) If the lower part of the pseudostem is still green but the rest of the plant is dead (Fig. 4), then the plant can potentially survive, although this is unlikely. The ability of the growing point and emerging leaves to break through the frozen part of the whorl is greatly restricted by dead tissue. Cutting off the dead part of the plant will enable the corn to continue its growth normally, but cutting the plants at the correct height is difficult as the mowing height would be very close to the soil surface.
- d) If the growing point is damaged the plants will not recover.
See also frost update
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