<br><div><section class="_135editor" data-role="paragraph" style="font-size: medium; max-inline-size: 100%; margin: 0px; padding: 0px; border: 0px none; z-index: 0; overflow-wrap: break-word !important; outline: none 0px !important;"><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 14px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉花具有无限生长的习性。山东棉区８、９月份的气温虽然能使棉株主茎不断生长，花蕾不断分化，但随着秋后气温的逐渐下降，这部分花蕾往往不能开花，即使成铃也不能成熟。另外，棉花开花结铃后，营养生长已逐渐衰退，主茎顶端的不断生长将抑制上部果枝的横向生长，花蕾因得不到足够的养分而大量脱落。适时打顶能改变养分运输方向，使原来运向主茎生长点的养分供应上部果枝，促进花蕾生长发育，提高成铃率，减少脱落。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 14px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉花打顶要因地、因时制宜，要根据地力、气候、品种和管理水平的不同区别对待。一般长势弱、密度大的棉田，打顶适当早些；长势强、密度稀、肥力大的棉田，可适当迟些。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 14px; overflow-wrap: break-word !important; outline: none 0px !important;">　　打顶的时期应尽量及时准确，打顶过早，会造成上部赘芽生长过多、过快，上部果枝伸展过长，影响通风透光，还限制了果枝数和果节数，减少了有效蕾铃，不能充分利用有效季节。打顶过晚，起不到调节养分分配的作用，使上部出现空果枝或结一些无效桃，导致迟熟减产。一般在７月中旬前后打顶。高产棉田７月２０日前后打顶，一般棉田应在７月１０日前后打顶，各类棉田为了充分利用有效结铃时间，打顶的最晚时间是７月２５日前后，这就是“时到不等枝”。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p></section><section class="_135editor" data-role="paragraph" id="autoparagraph" style="font-size: medium; max-inline-size: 100%; margin: 0px; padding: 0px; border: 0px none; z-index: 0; overflow-wrap: break-word !important; outline: none 0px !important;"><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; font-family: 微软雅黑, &quot;Microsoft YaHei&quot;, sans-serif; font-size: 17px; caret-color: rgb(255, 0, 0); overflow-wrap: break-word !important; outline: none 0px !important;"></p></section></div>