Winter wheat freeze-proof
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The current status of wheat from sowing to the present seedling stage is generally positive. There was a good sowing foundation, sufficient base fertilizer, high-quality varieties, concentrated sowing dates, high accumulated temperatures, adequate plant groups, strong individual growth, and promising pre-winter seedlings with high yield potential. However, several challenges have emerged, including slow seedling development, frost damage risks, drought stress, yellowing seedlings, and de-fertilization in some fields.
**I. Main Issues in Wheat Fields**
**(A) High Temperature, Excessive Growth, and Frost Risk**
Last winter saw unusually high temperatures, resulting in significantly higher accumulated temperatures from sowing to overwintering compared to normal. Before winter, many wheat fields were overly vigorous, with some even beginning to joint before the cold set in. When temperatures dropped, certain varieties and areas experienced frost damage, leading to seedling death and reduced yields. This year's situation appears more severe than last year, with an increased risk of frost damage.
1. **High Accumulated Temperatures**: In southern and central regions of our province, wheat sown before October 5th, especially early October, has already reached an accumulated temperature of 650°C by November 27th. In places like Shijiazhuang, wheat continues to grow into winter. National Climate Center experts predict a warm winter this year, meaning the accumulated temperature before winter will be even higher than usual.
2. **Excessive Leaf Age and Vigorous Growth**: Wheat sown before October 5th has developed up to 7 leaves, with some fields reaching 8 leaves, leaf lengths exceeding 20 cm, and plant heights around 30 cm. The population density exceeds 1 million per mu, and fields are almost fully closed. If the leaf age reaches 8–9, plants may start jointing before winter, greatly reducing cold resistance and increasing the risk of frost damage.
3. **Weak Winter Varieties**: Many weak winter varieties are being planted in areas like Shijiazhuang and southern regions. These varieties have poor cold tolerance, and last year, many areas experienced winter kill and seedling loss. This year’s conditions make the threat even greater.
4. **Early Sowing Dates**: In Shijiazhuang, about one-third of the wheat area was sown before October 5th, contributing to the problem of excessive growth and vulnerability to cold.
**(B) Drought Stress, Yellow Seedlings, and Nutrient Deficiency**
1. **Large Planting Area with Limited Water Supply**: In central and southern Anhui, wheat covers over 90% of the total area, but less than 20% of the land receives irrigation.
2. **Drought Conditions**: From October to November, the region experienced high temperatures and low rainfall, with precipitation below 20% of the average.
3. **Nutrient Deficiency and Yellowing Seedlings**: Due to excessive growth before winter, some fields suffered from insufficient base fertilizer, leading to yellowing and nutrient deficiency in the seedlings.
**II. Frost Damage Indicators and Impact on Wheat**
**(I) Growth Indicators for Pre-Winter Seedlings**
1. **High Plant Population**: A population of more than 1 million stems per mu indicates dense fields that are nearly closed.
2. **Excessive Leaf Age**: A main stem with more than 7 leaves is a sign of overgrowth and increased frost risk.
These two factors should be considered together. Even if the population is below 1 million, a large leaf count or high plant height should also be treated as overgrown (Wang Miao). Similarly, dense and closed fields with young plants should also be classified as such.
**(II) Effects of Frost Damage**
Frost damage can severely impact wheat yields through three main mechanisms:
1. **Physiological Damage**: Overgrown fields may suffer internal damage from cold, affecting ear development and reducing spikelet formation, which lowers yield.
2. **Leaf Damage**: Frost-damaged leaves dry out and die, leading to a "no gluten" condition, delayed spring growth, and lower productivity.
3. **Seedling Death**: In severely affected fields, entire plants may die, leading to a lack of panicles and significant yield loss, or even total crop failure.
**III. Key Measures to Control Wheat Growth**
1. **Repression of Overly Vigorous Fields**: Focus on fields sown before October 5th, especially those showing signs of overgrowth. If the ground is not frozen, repress the fields first before applying water. For fields with heavy growth, use methods like rolling or turbulence to control growth.
2. **Deep Rooting and Watering**: Combine deep root stimulation with repression to control root length and fill soil cracks.
3. **Applying Frozen Water**: This year, drought has been severe. Applying frozen water helps alleviate dryness and reduces frost effects. For fields with insufficient base fertilizer, combine it with fertilizers to replenish nutrients. For overly vigorous fields showing de-fertilization, apply repression, squatting, and chemical fertilizers to prevent the “no flourishing†issue.