Changes in Cotton Yield, Boll Development, and Growth in Response to Leaf and Terminal Removals at Various Growth Stages

Many natural occurrences have the potential to reduce cotton lint yield by causing physical damage to vegetative and reproductive plant tissues.  Mechanical damage to foliage, stems, and terminals from crusting, sandblasting, insect damage, animal feeding, and severe weather events can cause significant damage to stems and foliage at various stages of crop development.  More specifically, severe weather events such as hail storms have been observed to cause light to severe damage to many crops including cotton, and the associated crop injury often varies within a given agricultural field or across a farm due to the sporadic nature of the storms.  Whether attributed to biotic or abiotic factors, physical damage to terminals has the potential to delay maturity and reduce the yield and/or fiber quality of cotton.  Accurate estimation of lint yield loss following a particular stress requires an understanding of the propensity of the cotton plant to recover during the remainder of the growing season.  Estimating expected yield loss based on the timing and severity of crop injury is important for the purpose of grower compensation for insurance claims in the event of injury, replanting decisions for producers and consultants, and recommendations from university Extension personnel. 

 A replicated field trial was conducted at the PDREC located in Florence, South Carolina during the 2013, 2014, and 2015 growing seasons.  Treatments consisted of 17 different combinations of leaf and terminal removal based on cotton growth stages.  PHY 499 WRF plants were either completely defoliated (100% defoliation) or had half their leaves removed (50% defoliation) by hand at the 4-leaf stage, at matchhead square, at early bloom, and at early bloom plus 2 weeks.  Terminals were also removed by hand in combination with the defoliation treatments on half the plots during the same growth stages.  An untreated check was also included.