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四、返青——起身(中南部在2月下旬——8月20日,北部在3月上旬——3月下旬) 促进早春多分蘖,并整齐健壮,根系深扎,争取增加穗数。一般情况下,当日平均温度达0℃上下,最高温度5℃以上,5厘米(1寸半多)土层地温达0.5℃以上时,小麦开始返青,返青后开始分蘖,形成一个春季分蘖盛期。返青至拔节也是根系生长的主要时期,长出的次生根数占总根数的70—80％。此时小麦幼穗
Fourth, turn green - get up (Central South in late February - August 20, the north in early March - late March) to promote more tillering in early spring, and neat and tidy, deep roots tie, strive to increase the number of ears. Under normal circumstances, the average daily temperature of 0 ℃ up and down, the maximum temperature above 5 ℃, 5 cm (1 inch and a half more) soil temperature reached 0.5 ℃ above, the wheat began to turn green, turning green after tillering, the formation of a spring tillering peak . Rejuvenation to jointing is also the main period of root growth, the growth of secondary roots accounted for 70-80% of the total number of roots. Wheat ears at this time