The Occurrence of Spring Frost Damage in Wheat and How to Remedy It

Every spring in February and March, cold air often breaks out and moves southward in the north, with a large temperature drop during the process, and wheat that has jointed too early often suffers frost damage. At this time, for overly vigorous seedlings, the method of compaction should be adopted to inhibit growth; for weak seedlings, apply fertilizer reasonably to promote the weak and turn them strong, so as to enhance cold resistance. At the same time, pay attention to listening to weather forecasts, irrigate before the cold wave arrives, or organize large-scale unified smoking to prevent and reduce frost damage.

Wheat Is Not Cold-Tolerant After Jointing

Wheat is a relatively low-temperature-tolerant crop, but the cold resistance of wheat is related to the developmental stage it is in. At the seedling stage, during the “vernalization” stage, cold resistance is strongest; after completing “vernalization”, cold resistance declines further. When frost damage occurs, under the effect of low temperature, the water within the wheat's cell tissues freezes; when ice forms between cells, the volume increases and the cells are damaged. If the temperature drops further, ice also forms inside the cells, leading to death. After wheat joints, if it encounters a low temperature of -1°C to -4°C, the young spike may be frozen to death or form a deformed spike. The greater the range and steepness of the temperature drop, and the longer the low temperature lasts, the more severe the damage.

Check the Degree of Damage After Freezing

After wheat is frozen, check the degree of damage promptly; the focus of the inspection is the young spike. In plants whose young spikes have been frozen to death, the heart leaf no longer elongates, and most curl into a trumpet shape, while a few wither and die directly. But some frozen-to-death plants give a false impression: the leaves can still remain green, and some may not even turn yellow and withered until 10-15 days later. Therefore, the young spike should be peeled open further to look; if the young spike is found to be milky white and opaque, then it has already been frozen to death.

Remedial Measures

1. Do not plow up frozen wheat fields at will. Spring frost damage occurs in spring, when the wheat seedling root system is already well developed and the tillering nodes are relatively thick and strong. Even if the aboveground part of the plant is entirely frozen to death, the root system and tillers will not die. As long as management is strengthened, with the rise in temperature, new tillers will quickly grow out and can still head and set grain.

2. Do not cut off the frozen yellow leaves and “dead tillers”. Research shows that after wheat is frozen, within a certain period, the root system of “dead tillers” has a stronger ability to absorb fertilizer than that of living tillers. After the main stem and large tillers are frozen to death, the nutrients absorbed by their root systems can be transferred to the surviving tillers, which is of great benefit to frozen wheat seedlings in restoring vitality and increasing the number of tillers that form spikes.

3. Topdressing and watering. After wheat is frozen, the nutrients in the plant are consumed excessively and the seedlings are very weak. With the rise in temperature, new stems and tillers grow rapidly, requiring large amounts of water and nutrients. Water and topdress promptly; depending on the seedling condition, apply 5-7.5 kg/mu of urea, or spray a 1%-2% urea solution on the leaves, to promote recovery growth.