The causes of wheat seedling death in winter and spring can be broadly divided into endogenous and exogenous factors. Endogenous factors relate to the plant's inherent ability to resist cold and drought. Using varieties with poor cold tolerance increases the risk of seedling death. Planting too early can lead to premature spike differentiation, reducing the plant’s cold resistance. Seedlings that are weak or delayed may not accumulate enough sugars, making them more vulnerable to cold and drought stress, ultimately leading to death.
Exogenous factors include environmental conditions such as weather, soil quality, and improper farming practices. For example, insufficient rainfall in summer and autumn can result in low soil moisture, while dry winters and springs with little snow and frequent cold winds exacerbate drought conditions. Sudden temperature fluctuations can also damage wheat seedlings. In saline soils, high salt content can cause physiological dehydration, further increasing mortality. Choosing weak winter-hardy varieties or sowing at inappropriate times—too early, too late, too deep, or too dense—can lead to weak seedlings, which struggle to survive the winter. Lack of sufficient groundwater or failure to apply frozen water can also cause early freezing and seedling death.
To reduce seedling death, several cultivation measures can be implemented. First, selecting cold-resistant wheat varieties is one of the most cost-effective strategies. Local farmers should choose varieties suited to their region, ensuring they have both high yield potential and adequate cold tolerance. Before planting, it's essential to understand the characteristics of each variety.
At the seedling stage, if irrigation is insufficient, watering during the tillering phase can help promote healthy growth. If the soil lacks nutrients, a small amount of fertilizer can be applied to support early growth, encouraging strong root development and large leaves, which aid in winter survival. However, overwatering should be avoided, as it can interfere with the cooling process of the plants.
Winter irrigation is crucial for maintaining soil moisture and improving thermal capacity. It helps seal the topsoil, promoting root growth and reducing the risk of cold and drought-related seedling death. Proper timing is important—frozen water should be applied when temperatures drop to around 4°C. Clay soils should be irrigated earlier to prevent freezing before water infiltration, while sandy soils should be irrigated later. In wetlands, rice fields, or low-lying areas, irrigation can be adjusted accordingly. For fields with pest problems, frozen water can also help control pests by breaking up the soil.
Timely rolling of wheat fields can promote root development by breaking up cracks, solidifying the soil, and strengthening the bond between roots and soil. Additionally, covering the wheat with a thin layer of soil or sand during winter can protect the lower leaves, reduce soil moisture evaporation, and improve the microclimate around the tiller zone. A 1–2 cm layer of cover soil can provide effective frost protection. The cover should be removed when the temperature reaches around 5°C in spring. For weak or late-sown wheat, covering is especially important, as it helps protect against frost, promotes faster growth, and enhances tiller development. Covering at 3°C allows for early growth, but covering too late may result in leaf freezing. For late-sown wheat, covering after sowing can provide additional warmth and protection.
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