Causes and Defense methods of Frost injury of Wheat with poor drought Resistance and easy Frostbite

The external cause of wheat freezing is poor weather conditions, and the internal cause is poor cold resistance. According to the occurrence period and characteristics of wheat freezing injury, it can be divided into four types.

Wheat is frozen

The types of freezing injury of wheat: (1) in the early stage of overwintering (early and middle December), wheat seedlings did not exercise cold resistance, and suddenly encountered the weather of sudden drop in temperature and lower than-5 ℃, resulting in weak seedling quality, poor soil preparation quality, large soil voids and rapid withering of seedlings in dry fields. (2) during the overwintering period (from the end of December to the first ten days of February of the following year), strong cold currents or abnormal weather lead to the alternation of freezing and thawing. There are two cases, one is the aboveground withering of wheat, the other is the rise of air temperature, the cold resistance of wheat seedlings decreases after the young spike sprouting, and it is easy to be frozen when the temperature drops. (3) from turning green to jointing stage (from mid-February to early March), the growth of wheat seedlings is accelerated, and the cold resistance decreases. In case of cold current, the seedlings are easy to freeze to death. (4) the wheat from jointing to heading stage (mid-March to early April) has strong growth and weak cold resistance. in case of a sudden drop in air temperature, it is easy to be frozen, and the young ears of the main stem and large tillers are frozen to death.

Causes: (1) climatic factors. The high temperature before winter leads to the vigorous growth of wheat seedlings, the sudden drop in temperature during the overwintering period, and the strong cooling and continuous low temperature make the unhardened wheat frozen. (2) breed factor. The cold resistance of wheat varieties with strong spring is poor, which increases the risk of freezing injury. (3) sowing factors. The suitable sowing time of wheat in central Jiangsu is from the end of October to the beginning of November, but there are often rainy or dry days at this stage, so it is difficult to ensure timely sowing. If sowing early, the wheat seedlings will grow in the early stage, and when the freezing injury comes, the wheat seedlings will be seriously damaged. (4) tillage factors. In order to grab soil moisture and sow seeds, extensive tillage, wheat seeds fall deep into the soil, elongate seedling emergence time, and form weak seedlings; or the soil mass is large and hard, which is not conducive to root binding, and it is difficult for wheat seedlings to absorb fertilizer and water, resulting in poor quality of wheat seedlings, while cold air is easy to invade the root system of frostbite under the soil; covering the soil is not easy to form open-seeded seedlings; the root system is shallow into the soil, vulnerable to freezing damage; the ditch system is not matched, poor drainage, prone to freezing. (5) Fertility factor. When sowing, the amount of fertilizer application is too large, resulting in wheat seedlings growing before winter, prone to freezing injury; while in fertilizer-deficient fields, wheat seedlings are yellow and thin, poor cold resistance, and easy to be frozen when the temperature drops suddenly.

Defense countermeasures: (1) improve the quality of sowing. Select wheat varieties with good cold resistance, apply rotten organic fertilizer 1500-2000 kg per mu, 45% ternary compound fertilizer 35-45 kg per mu before sowing, and fine soil preparation after deep ploughing. The seeds were selected, dried and germinated, and the seeds were mixed with chemicals. Sowing at the right time according to the characteristics of the variety, reasonably determine the sowing rate, sowing depth of 3-4 cm to ensure consistency of depth.

(2) strengthen field management. It is necessary to irrigate the fields after sowing, such as soil consolidation, timely ploughing and loosening the soil; after emergence, timely dense and sparse, dredge the three ditches, and see the seedlings apply wax fertilizer; properly suppress before overwintering, close the soil cracks, in order to preserve soil moisture. Winter irrigation before the cold current can increase soil temperature, close soil cracks, promote more tillers, grow tillers and grow seedlings. Covering grass in the field after winter irrigation and fertilization is beneficial to preventing wind, freezing, heat preservation and soil moisture conservation.

(3) to prevent the growth before winter. The early sowing fields can be properly suppressed to inhibit the growth of wheat main stem and large tillers, and if necessary, growth regulators should be sprayed; if the sowing rate is too large, seedlings should be thinned first, then combined with watering, and appropriate amount of available nitrogen and phosphorus fertilizer should be applied; if the fertilizer and water is excessive, 7cm can be hoed deep between rows during the 5-leaf stage of wheat seedlings, cutting off part of the secondary rooting and controlling nutrient absorption.