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LOGO: Journal of Cotton Science


The Impact of Variable, Cold Minimum Temperatures on Boll Retention, Boll Growth, and Yield Recovery of Cotton

Authors: Stephen J. Yeates, Mike F. Kahl, Andrew J. Dougall, and Warren J. Müller
Pages: 89-101
Agronomy and Soils

A previous field experiment reported that cotton grown in the tropical dry season, where minimum temperatures during flowering can be cold (< 10°C), yielded a greater proportion of cotton from bolls pollinated when minima were warmer. The retention and growth of bolls was postulated to be reduced by cold night temperatures. However, biotic stresses (e.g., pests) might have confounded this response. Reported herein is a pot experiment where biotic stresses were effectively removed. Over two seasons, (i) ambient and (ii) ambient plus 5 to 6°C (range 10- 24°C), night thermal conditions were imposed from 1 wk prior to first flower to 2 wk after last effective flower. Day temperatures were the same. Average ambient minimum temperature for the treatment period was 12.6°C (range 5.9-21.1 °C) and 10.2°C (range 2.6-21.0°C) in 2003 and 2004. Flowers were damaged by low ambient minimum temperatures occurring near anthesis, which led to shedding or lower seed number per boll which reduced boll size. The latter could be due to poor pollination and competition for assimilates. Shedding was correlated (p < 0.01) with minimum temperature at anthesis with < 40% survival when minima were < 6°C. Seed cotton yield was the same. It was concluded that the yield recovery from variable, low minimum temperatures during flowering was (1) similar to where damage to fruit was biotic with compensation occurring on later flowering fruiting sites provided temperatures were warm; and (2) unlikely to be impacted by damage to photosynthetic apparatus due to the minimum temperatures observed here.