Photosynthetic Characteristics of Cotton Are Enhanced by Altering the Timing of Mulch Film Removal 

Abstract Background: The photosynthetic parameters of cotton plants may be modified by the timing of film-removal during their growing period. This study was undertaken during 2015–2017 in Xinjiang, China, to determine to what extent the film mulching removal time—1 and 10 days before the first irrigation and 1 day before the second irrigation after seedling emergence—influenced cotton’s photosynthetic characteristics. The control group consisted of film mulching present throughout the growing period. Results: The results suggested the following: (1) Removing mulching-film within 50 days of seedling emergence had adverse effects on soil temperature and moisture. (2) Film-removal before the first or second irrigation after emergence improved the net photosynthetic rate in cotton’s later flowering stage and its transpiration rate in mid and later flowering stages, while enhancing the actual electron transport rate (ETR) and maximum electron transfer rate (ETRmax) between cotton photosystems I and II. (3) Film-removal treatment post-emergence also increased cotton plants’ tolerance to high irradiation, a trend more pronounced in the early flowering stage in wetter years. (4) Leaf area index (LAI) of cotton was reduced in the film-removal treatment, for which the greatest maximum accumulation of dry matter occurred in a drought year (i.e., 2015). (5) Film-removal increased lint cotton yield, except in dry year (2015). Conclusions: Film-removal can improve cotton’s fiber quality to a certain extent. Collectively, our study’s experimental results indicate that applying mulch film removal at an appropriate, targeted time can improve photosynthesis and yield of cotton crops.