Cotton Root Morphology and Dry Matter Accumulation at Different Film Removal Times

Abstract

Core Ideas Film removal at an appropriate time can increase cotton root length, surface area, and volume. Film removal is conducive to the accumulation of root dry matter in the year with less rainfall. Film removal treatment promotes growth of hair roots and improves the root/shoot ratio. A field experiment was conducted to examine the influence of mulch film removal time (10 and 1 d before the first irrigation (T10 and T1, respectively) and 1 d before the second irrigation (E1) after emergence) on cotton (Gossypium hirsutum L.) root morphology and dry matter accumulation. The control group (CK) was film mulched throughout the growth stage. In 2015, the respective root length density (RLD), root surface‐area density (RSD), and root volume density (RVD) in E1 were highest during the initial flowering stage (IFS, 3537 m m−3, 3.4819 m2 m−3, and 382 cm3 m−3) and blossoming and boll forming stage (BBFS, 2472 m m−3, 3.1307 m2 m−3, and 421 cm3 m−3). The maximum root dry matter accumulation was measured in CK (2647 kg ha−1). In 2016, which had more rainfall, RLD (1699 m m−3) and RSD (2.6877 m2 m−3) in T10 and RVD in T1 (503 cm3 m−3) were the highest during IFS. RLD in E1 (2234 m m−3), RSD (3.6770 m2 m−3) and RVD (598 cm3 m−3) in CK were the highest during BBFS. The cotton root/shoot ratio (R/T) was higher in the film‐removal treatments than in CK. E1 showed the highest proportion of fine roots thinner than 1.0 mm during any stage except for 2015 BBFS. The results indicate that film removal at an appropriate time can increase RLD, RSD, and RVD, but it is conducive to the accumulation of root dry matter only in years with lower rainfall.