8月下旬至10月上旬,为春夏红薯块根膨大期,此时是产量形成的关键期,更是需肥最多期,可用以下3法追肥。(1)孔眼追肥法。用一块木橛,在离其主根20～30cm处,打一深30cm左右的孔眼,放入适量三元素复合肥,并用湿土封好,若在其垄两侧各打一个孔,效果更佳。此法每667m2增产20%左右。(2)裂缝追肥法。红薯膨大地面出现裂缝时,每667m2用500g磷酸二氢钾,加水400kg, From late August to early October, it is the key period for the production of sweet potato tubers in spring and summer. (1) hole top dressing method. With a piece of clogs, 20 to 30cm away from its main root, hit a hole about 30cm deep, into the amount of three-element fertilizer, and sealed with wet soil, if the ridge on both sides of each play a hole, the better . This method yields about 20% increase every 667m2. (2) crack top dressing method. Sweet potato swelling on the ground cracks, every 667m2 with 500g potassium dihydrogen phosphate, add water 400kg,