Winter wheat freeze-proof
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The current status of wheat from seeding to the present seedling stage is generally favorable. There was a good sowing foundation, sufficient base fertilizer, high-quality varieties, concentrated sowing dates, and a high accumulated temperature, leading to robust seedlings with strong individual growth and high yield potential before winter. However, several challenges have emerged that require immediate attention.
I. Main Issues in Wheat Fields
(A) High Temperature, Excessive Growth, and Frost Risk
Last winter, due to higher-than-normal temperatures, the accumulated temperature from sowing to overwintering was significantly above average. As a result, many wheat fields were in a vigorous growth phase before winter, with some even beginning to joint. When winter temperatures dropped, some varieties suffered frost damage, leading to dead seedlings and significant yield losses. This year’s situation is more severe than last year, with a greater risk of frost damage.
1. Elevated Temperatures and Accumulated Heat: In the southern and central parts of the province, wheat sown before October 5th has already reached an accumulated temperature of up to 650°C by November 27th. In areas like Shijiazhuang, wheat continues to grow through the winter. Experts predict a warm winter this year, which means the accumulated temperature before winter will be even higher.
2. Excessive Leaf Age and Vigorous Growth: Wheat sown before October 5th has shown leaf ages of up to 8, with leaves longer than 20 cm and plant heights around 30 cm. The population density exceeds 1 million per mu, and fields are densely packed. If plants reach 8–9 leaves, they may start jointing before winter, significantly reducing cold resistance and increasing the risk of frost damage.
3. Weak Winter Varieties: Many weak winter varieties are being grown in Shijiazhuang and southern regions. These varieties are prone to winterkill, as seen in several counties last year. With the current conditions, the threat is even greater.
4. Early Sowing: In Shijiazhuang, about one-third of the total area was planted before October 5th, contributing to the problem of excessive growth.
(B) Drought, De-fertilization, and Yellow Seedlings
1. Large Planting Area with Low Water Supply: In central and southern Anhui, the planting area is extensive, with some regions covering over 90% of the land. However, water supply for irrigation is less than 20% of the total.
2. Dry Weather: From October to November, the region experienced high temperatures and low rainfall, with precipitation below 20% of the average.
3. Nutrient Deficiency: Due to heavy growth before winter, some wheat fields lack sufficient base fertilizer, leading to yellow seedlings and poor health.
II. Frost Damage Assessment and Its Impact on Wheat Before Winter
(I) Indicators of Pre-Winter Seedling Development
1. High Population Density: A stem count of over 1 million per mu indicates dense growth, with most fields fully closed.
2. Excessive Leaf Age: A main stem with more than 7 leaves suggests overgrowth, increasing the risk of frost damage.
These two indicators should be considered together. Even if the population is slightly below 1 million, if the leaf age is too high or the plant height is excessive, it still qualifies as overgrown.
(B) Effects of Frost Damage
Frost damage can severely impact wheat yields through three main mechanisms:
1. Physiological Damage: Overgrown fields exposed to late winter cold show no visible symptoms, but ear development is affected, leading to fewer spikelets and lower yields.
2. Leaf Damage: Frost-damaged leaves dry out and die, causing a “no gluten†phenomenon. This leads to slow regrowth in spring and reduced production.
3. Seedling Death: In highly vigorous fields, cold resistance is nearly lost. Some plants may die completely, resulting in insufficient panicle numbers and significant yield loss, or even total crop failure.
III. Key Measures to Control Wheat Growth
(1) Implementing Field Compression: For fields sown before October 5th, especially those showing signs of overgrowth, field compression measures should be intensified. If the ground is not frozen, compression should be done first, followed by freezing. For extremely vigorous fields, methods such as rolling or turbulence can be used.
(2) Deep Rooting and Compression Combined: Deep rooting can help control root length and fill soil cracks, improving overall plant resilience.
(3) Applying Frozen Water: This year, drought stress is severe. Applying frozen water can help alleviate drought and reduce frost effects. It also helps replenish nutrients in fields with insufficient base fertilizer. For overly vigorous fields, combining compression with frozen water and chemical fertilizers can prevent the “no flourishing†phenomenon.