采用覆土的方法,把越冬苗木埋在土中,减少外界不良因子的影响,保持苗木内部的水分平衡,可使苗木安全越冬。这种方法简便易行,成本低,适用于油松、樟子松,红松等苗茎较短而带有弹性的苗木。 覆土要在霜降后立冬前(10月末～11月初)进行。过早天气暖和,地温尚高,易使苗木受热,甚至霉烂。过晚土壤结冻,覆土盖不严,往往因透风造成苗木受冻而死亡。 在土壤结冻前两三天灌足底水,用铁锹将步道土(垄作用垄沟土)抢起并敲打细碎,或用大梨将步道土(或垄沟土)趟起打碎,往床(垄)的一方压土。压土要从苗木侧方进行,切忌从苗木头上盖土,要使苗木向一侧倾斜,以防碰伤顶芽。覆土厚度要超过苗梢3～4厘米。覆土后用耙将土搂平、拍实,防止透风。 翌春撤土不要过早或过晚,过早春风大,蒸腾作用快,而使苗木体内水分消耗很多,但土壤仍未解冻,苗根不能从土壤中吸收水分,造成水分失调,致使苗木死亡。过晚土壤已解冻,气温、地温上升较快,苗木受潮 The use of soil cover method, the overwintering seedlings buried in the soil, reducing the impact of adverse factors outside the nursery stock to maintain the water balance, seedlings can be safe winter. This method is simple and easy, low cost, suitable for Pinus tabulaeformis, Pinus sylvestris, pine and other seedlings shorter and flexible seedlings. Cladding to the beginning of winter before the frost (late October ~ early November). Premature weather is warm, the ground temperature is still high, easy to heat the seedlings, or even rotten. Too late soil freezing, cover soil is not strict, often due to ventilation caused by cold and death of seedlings. Two or three days before the soil is frozen, the bottom of the water is filled with shovels, and the shovel soil (ridge-furrow soil) is grabbed and smashed with a shovel, or the pathways (or furrows) Ridge) on one side of the pressure soil. Pressing the seedlings from the side, should not cover the soil from the seedlings, to make the seedlings tilt to the side to prevent bumps head buds. Cover soil thickness to more than 3 ~ 4 cm. After the soil rake with the soil will hug flat, shoot reality, to prevent the ventilation. Spring next spring should not be too early or too late, too early spring breeze, fast transpiration, leaving the seedlings consume much water, but the soil has not yet been thawed, seedling roots can not absorb moisture from the soil, resulting in water imbalance, resulting in death of nursery stock . The soil has been thawed too late, temperature, ground temperature rise rapidly, seedlings damp