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据研究,小麦拔节以后,5日内抗冻为急剧下降,拔节后10～15天,抗寒能力最弱。这时遇到最低气温1℃时,就可能发生轻度冻害;若气温低于零度以下就会造成重霜冻。冷空气南下,引起平流降温,夜间晴朗无风或微风,地表及植株表面大量辐射失热,便预示着霜冻的到来。冻害的程度因地形、低温强度和持续时间而不同。盆地、洼地、坡地下部和山谷等处,地势低洼闭塞,冷空气容易堆积,霜冻发生较为频繁、严重,持续时间也较长。干旱土壤冻害重于湿润土壤。
According to the study, after jointing wheat, the frost resistance dropped sharply within 5 days, and the weakest cold resistance ability ten to 15 days after the jointing. At this time encountered the minimum temperature of 1 ℃, it may occur mild frost damage; if the temperature below zero will cause heavy frost. Cold air south, causing advection cooling, sunny at no wind or breeze, a large number of surface radiation and plant heat loss, it indicates the arrival of frost. The degree of frost damage varies with topography, low temperature strength and duration. Basins, depressions, slopes and valleys and other places, low-lying blockage, easy accumulation of cold air, frost occurred more frequently, serious, longer duration. Arid soil is harder than moist soil.