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立冬至小雪期间,是预防翌年春旱的关键时期。大量旱灌试验证明,易旱地区这时只要抓紧进行冬灌,实行春墒冬补,就可以保证适时春播。据试验,冬灌水渗入耕地壤土层0.8~1.0米深并达到饱和时,采取一定的保墒措施,到第二年春播时,耕层土壤含水量仍可为15~20%(最适播期含水量),而未灌的土壤水分一般只有8%左右。这表明,冬灌补助春墒的作用是非常显著的。初冬时节,土壤夜冻昼化,容易灌足水。进入冬季后,由于气温下降,冰封大地,上壤水分蒸发大为减少。一般耕地土壤每日耗水量只有0.3~0.5
During the winter and winter snowfall, it is a crucial period to prevent the spring drought next year. A large number of drought irrigation experiments show that the drought-prone areas at this time as long as the pay close attention to winter irrigation, the implementation of spring moisture supplement, you can ensure that timely sowing. According to the experiment, winter irrigation water infiltrated into the soil layer 0.8 ~ 1.0 m deep and reached saturation, to take some measures to protect soil moisture, spring sowing the next year, the topsoil moisture content can still be 15 to 20% (sowing date Water), while not irrigated soil moisture is generally only about 8%. This shows that the role of winter irrigation to help sowing moisture is very significant. Winter season, the soil is frozen at night, easy to fill enough water. Into the winter, due to the temperature drop, frozen earth, soil moisture evaporation greatly reduced. Average soil daily water consumption of cultivated land is only 0.3 ~ 0.5