棉花播种期的选择是一件很重要的工作。播种过早,苗棉有受晚霜为害的危险,且种籽在土壤内时间过长,有腐烂和被害虫吃掉的可能;播种过晚,春季蒸发量大,保墒不易,造成缺苗。种籽必须在表土充分温热的情况下才会发芽,在5厘米深地温达到10—12℃,并掌握在晚霜期刚过去时棉苗就出土。玛纳斯河流域一般的晚霜期均在4月底与5月初,5厘米地温在4月20日左右即可达到10—12℃,故该垦区在4月18日至25日 The choice of cotton sowing time is a very important task. Sowing too early, Mian Mian risk of night cream damage, and the seeds in the soil for too long, rot and pest eaten possible; sowing too late, large amount of evaporation in spring, soil moisture is not easy, resulting in lack of seedlings. The seed must germinate only when the topsoil is sufficiently warm, reaching a temperature of 10-12 ° C at a depth of 5 cm, and mastery of the cotton seedlings unearthed just after the frost period has passed. Manas River basin generally frost-day period in late April and early May, 5 cm ground temperature around April 20 to reach 10-12 ℃, so the reclamation area in April 18 to 25