Occurrence Characteristics and Remedial Measures of Spring Frost Damage in Wheat

Every year in February and March of spring, cold air frequently breaks out and moves southward in the north, with large temperature drops during the process, and wheat that has jointed too early often suffers freeze damage. At this time, for seedlings growing too vigorously, the method of pressing should be adopted to inhibit growth; for weak seedlings, reasonable topdressing should be applied to promote weak ones into strong ones, 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-area unified smoking, so as to prevent and reduce freeze 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 its developmental stage. At the seedling stage, cold resistance is strongest during the “vernalization” stage, and after completing “vernalization”, cold resistance further declines. When freeze damage occurs, under the action of low temperature, the water within wheat cell tissues will freeze. When ice forms between cells, the volume increases, and the cells are damaged. If the temperature drops further, ice will also form within the cells, leading to death. After wheat joints, when it encounters a low temperature of -1°C-4°C, the young spike may be frozen to death, or malformed spikes may form. The greater the range and steepness of the cooling process, 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, with the focus on the young spike. For plants whose young spikes are frozen to death, the heart leaf no longer elongates, most curl into a trumpet shape, and 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, so further peel open the young spike 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 all the aboveground parts of the plant are frozen to death, the root system and tillers will not die. As long as management is strengthened, new tillers will quickly grow as the temperature rises, and they 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 live 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 greatly beneficial for frozen wheat seedlings to recover vitality and increase the number of tillers that form heads.

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