| ||Hail damage on cereal crops | Frost damage to cereals
Hail Damage on Cereal Crops
A cereal crop will recover from severe hail if damaged before the end of the tillering stage. This damage is confined to loss of leaf tissue. The stems and younger leaves will develop nearly normally. There is an adverse effect on yield that increases as the crop develops because of greater loss of leaf tissue and extra time needed for the plant to replace damaged tissue.
Hail damage after the stem extension or shooting stage damages the growing points and has a drastic lowering effect on yield. Recovery depends on the growth of new tillers from crown buds. Chances for recovery decrease as the crop develops, and, if a crop is badly hailed after heading, salvage for silage or hay may be the best course of action. The nitrate content of the fodder may be dangerously high for feeding and samples should be analyzed before use. If nitrate content of the hay or silage is too high to be fed safely, it must be mixed with other feed to reduce the average nitrate content to below 0.5%. A nitrate level of 0.5 per cent in feed is potentially dangerous: 0.75 percent will reduce milk production, 1.5 per cent is often lethal.
Frequent light hailstorms that partially damage a crop will cause more damage in some varieties than in others. Fewer stems are broken by such storms in the two-rowed varieties than in most of our six-rowed varieties of Barley. Triticale seem particularly resistant to hail damage, but can still be completely destroyed.
Frost Damage to Cereals
Frost damage to cereals in the fall can be avoided in most areas of Alberta by seeding early. In areas with short growing seasons, the probability of damage from fall frosts can be reduced by planting early-maturing varieties such as Conlon, CDC Kindersley, CDC Mayfair, or Tradition barley, AC Splendor or Park wheat or CDC Dancer or Lu Oat. Late April and early May seeding will occasionally expose the young crop to freezing temperatures while it is in the seedling or tillering stages. However, cereals can withstand very low temperatures while they are still in this vegetative stage. Damage will depend on the intensity and duration of the freezing period, but a temperature of around -8 degrees Celsius is required to kill the leaves of seedlings. Early May temperatures are rarely this low, and, even when the young leaves are damaged, recovery is usually complete because the growing point is protected from damage by being below the soil surface, at the crown level.
If the leaves are completely frozen off, reseeding is hardly ever necessary. Regrowth will occur quite quickly as the frozen plants have their established root system and growing point to rejuvenate from. The regrowth is much faster than it would be from reseeding and much less expensive. A delay in maturity will result but not nearly as much delay as that which would occur as a result of reseeding.
Susceptibility to frost damage increases with increasing plant development, but the probability of severe frost decreases as the season advances. Freezing temperatures will very rarely occur in June after the crop has started to shoot and the growing points are no longer well protected. Exposure to frost at this stage will kill the very tender and immature heads. Recovery for grain production will require regrowth from the crowns. This will delay maturity and lower grain yields. By the onset of flowering, a frost of 0 degrees Celsius to -2 degrees Celsius is sufficient to damage the young florets and result in partial or even complete sterility in the heads. Early seeding or the use of early maturing varieties will not avoid damage from such very late spring frosts, but they happen so rarely that they should not deter one from seeding early.
Cereal crops are most frequently damaged by frost in the fall when the crop is filling or maturing. Symptoms of the damage are seldom obvious as the developing kernels are killed and the leaves are apparently unharmed. The kernels do not develop further after freezing, and yield loss depends directly on the stage of filling, with losses decreasing with advancing maturity.
When a barley crop has filled but has not yet dried and ripened, there is no obvious damage from a killing frost. There is little or no effect on yield and the kernels appear nearly normal, However, frozen grain will not germinate and is useless for seed or malting.
When a crop is frozen at the flowering stage or later, it can be harvested as hay or silage. The sudden stoppage of growth may result in fodder with excessively high nitrate content (0.5% or more), and should be tested to determine how safe it is to feed. Hay containing high levels of nitrates can still be salvaged for feeding by mixing with low-nitrate hay to dilute the overall nitrate levels. If the kernels are filled and the grain harvested in the usual way, it is probably safe.