Since late December 2004, three consecutive rain and snow processes have occurred in Anhui Province, and drought conditions have eased, but the temperature has continued to be low. From late December to early January, the temperature in the northern Huaihe River region is 3 to 4°C lower than the same period in the normal year. On the 1st, the minimum temperature in the Huaibei area reached -9 to -11°C, and the JAC reached -6 to -8°C. As a result, some wheat suffered from different degrees of frost damage.
First, the causes of cold injury, classification and characteristics
This year's winter wheat frost damage mainly due to two reasons: First, the pre-winter temperature is high, the effective accumulated temperature in the province from early October to early December increased by about 150 °C over the same period of the year, including the first half of November and the first ten days of December respectively. High 4-5 °C, resulting in part of the wheat growth is too fast, the stage of development in advance, without cold-resistant exercise, frost resistance is weak. The second is that it has experienced significant temperature reductions just after it entered the wintering period, and it has been caused by continuous low temperatures. Wheat freeze injury can generally be divided into four levels. The primary frost damage is a slight frost injury, which is mainly manifested by the tip of the upper 2 or 3 leaves or the leaves less than 1/2 of the leaves being frozen and yellowed; the second and third-level freeze injury is mainly characterized by more than half of the leaves being frozen and browned; the fourth-grade freezing injury is serious. Freezing damage is mainly manifested in that more than 30% of main stems and large branches are frozen, jointed, and the stems are partially frozen, and young ears lose water, wilt, and even die. According to local surveys, most of the province's wheat showed first-grade frost damage, followed by second- and third-grade frost damage, and four-level frost damage occurred in individual plots. In general, the area of ​​frozen damage to wheat in Huaihe district is smaller than that in Huaibei area, but the degree of frost damage is heavier than in Huaibei area. The reason for this analysis is mainly due to the large proportion of spring varieties in the area.
According to the survey and analysis, this year's wheat freeze injury has the following characteristics:
The first reason is that sowing is too early and the development of early-stage wheat is heavier than freezing, and wheat sowing at a proper time is lighter.
The second is that the spring varieties, especially those with strong springiness, have a large area of ​​frost damage and heavy damage. Among the 24 species surveyed, there are different degrees of frost damage. The cold injury is mostly spring-type, and the semi-winter varieties are lighter. Among the spring varieties, Zheng 9023, Yanzhan 4110, Yumai 18, and Wanmai 44 had a large area of ​​frost damage. The degrees of freezing damage were Zhengmai 9023> Yanzhan 4110> Yumai 18> Wanmai 44, and Zhengmai 9023 suffered freezing damage. Heavier, more than 44 buckwheat for the first and second degree of minor frost damage. Among the semi-wintering cultivars, the buckwheat 38, buckwheat 19, and Yannong 19 also had some degree of frost damage, mostly one or two, and the degree of cold injury was lighter.
Third, the quality of planting and sowing volume affect the degree of frost damage. The poor quality of the site preparation, the large seeding rate, and the thin field of wheat seedlings caused heavy damage.
Fourth, the amount of fertilizer is too large and the nitrogen fertilizer is used as a base fertilizer for one-time use. The wheat leaves are covered under the leaves and the fertilizer is very prosperous. The freezing injury is heavier.
Fifth, the anti-freezing effect of the plots with repression and other control measures before the winter was significant, and the cold damage was lighter. The cold-damaging of the plots that did not adopt the control measures was heavy. In particular, the cold damage of the plots prior to the winter jointing was generally heavier.
Second, the impact of frost damage and remedial measures
Because this frost damage occurred early in the winter and earlier in the season, and wheat has a stronger self-regulatory capacity, it has more room for maneuver. In the case of a slightly frost-damaged field, the growth in the later stage is basically unaffected; as long as the management of the second and third frost damage fields is strengthened, the impact on the yield is not significant; in the case of a field with severe frost damage at the fourth level, timely recovery measures can still be obtained. Even if more than 80% of the main stem and Oita were frozen to death, as long as the childbirth day was not frozen, remedial measures were taken to strengthen management in the early spring and in the middle and later stages, and a good harvest could still be achieved. The main remedial measures are:
1. Early application of fertilizer to promote the early birth of newborn babies after freezing. If the main stem and part of the large shoots are frozen to death, fertilizer should be applied as early as possible. After the beginning of spring, the temperature rises. According to the fertilization of different wheat fields, 7 to 10 kg of urea can be applied per acre to promote the early birth of the new small tiller to ensure the growth of the wheat tiller. Adequate nutrients enhance the wheat's ability to resist cold temperatures in spring.
2, turn green to get up as appropriate fertilizer supplements to promote the recovery of frozen wheat leaves vitality. For the frozen tips of wheat leaf tip and leaves, it is necessary to apply 5 kg of urea per mu after returning to the beginning of the growing season to promote normal growth of the wheat seedlings as soon as possible.
3, suppress the control of Wang, re-apply joint fertilizer, ensure the steady growth of wheat. For wheat fields with minor frost damage and large groups (with more than 1 million mu of stems), the control of the cracks may be carried out before the early spring wheat rises. (When repressing, pay attention to frost and dew in the morning, and do not repress if the soil moisture is too high. ). This type of wheat field due to the consumption of soil nutrients more should be appropriate to reapply joint fertilizer, urea 10-12 kg per acre, can be seen in the jointing to the booting before the rain spread. In case of soil drought, when the water holding capacity in the field is below 50% to 60%, the irrigation areas must be filled with water in time.
4, timely scratch, promote growth. According to the conditions of the seedlings, meteorological conditions and soil moisture conditions, etc., timely ploughing and warming and protecting the wheat seedlings to make up for freezing injury. Three-pass wheatgrass, with less disease and fewer bugs, grows well in the early spring. It can eliminate weeds, make water and fertilizer use more concentratively, reduce the occurrence of pests and diseases, eliminate soil compaction, loosen and increase soil permeability. Promoting the development of wheat roots is conducive to the robust growth of plants. Paddles can be combined with topdressing.
5. Strengthen the control of late-stage disease, insects, and waterlogging in wheat fields, prevent premature aging, and harvest bumper crops.