Occurrence of Spring Frost Damage in Wheat and Remedial Measures

Every year in February and March of spring, cold air frequently 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 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 smoke generation, thereby preventing and reducing frost damage.

1. 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, cold resistance is strongest during the “vernalization” stage, and after completing “vernalization”, cold resistance further declines. When frost damage occurs, under the action of low temperature, the water in the wheat cell tissues will freeze. When ice forms between cells, the volume increases, and the cells are damaged. If the temperature drops further, the inside of the cells will also freeze, leading to death. After wheat jointing, when it encounters a low temperature of -1℃-4℃, the young spike may be frozen to death, or deformed spikes may form. The greater the amplitude and steepness of the cooling process, and the longer the low temperature lasts, the more severe the damage.

2. Check the degree of damage after freezing. After wheat is frozen, promptly check the degree of damage, 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 directly wither and die. However, some frozen-to-death plants give a false impression: the leaves can still remain green, and some may not even turn yellow and dry until 10-15 days later. Therefore, 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.

3. Remedial measures. 1. Do not arbitrarily plow up frozen wheat fields. Spring frost damage occurs in spring. At this time, 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 completely frozen to death, the root system and tillers will not die. As long as management is strengthened, with the rise of temperature, new tillers will quickly grow out, and it 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 fertilizer-absorbing capacity than that of live tillers. After the main stem and large tillers are frozen to death, the nutrients absorbed by their root system 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, nutrients in the body are consumed excessively, and seedling vigor is very weak. With the rise of temperature, new stems and tillers grow rapidly, requiring large amounts of water and nutrients. Timely irrigation and topdressing are needed. According to seedling condition, apply 5-7.5 kg/mu of urea, or spray a 1%-2% urea solution on the leaves, to promote recovery growth.