Growth and yield of cotton in response to waterlogging

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Cotton is known to be poorly adapted to waterlogged conditions. In Australia, cotton production is concentrated on soils with inherently low drainage rates, which, combined with the almost exclusive use of furrow irrigation and a summer dominant rainfall pattern, results in a significant risk of intermittent waterlogging. Three field experiments were conducted in which cotton was subjected to intermittent waterlogging by extending the duration of irrigation events. Timing of waterlogging, cultivar and landforming were also varied. Treatments required to generate significant impacts on crop growth and yield were more extreme than previously reported. Possible reasons for this are discussed. Consistent with the literature, yield loss was associated with reduced boll number ( R 2=0.82). The reduction in boll number was commensurate with the reduction in total plant dry matter: dry matter was reduced by up to 32% with the allometric ratio between boll number and glucose adjusted dry matter being unaltered by the treatments. The reduction in dry matter was due to lower radiation use efficiency (RUE g), which fell by up to 35%, rather than lower light interception. While leaf area was reduced, the resultant change in cumulative light interception was less than 5%. Thus, yield loss was caused by a reduction in the number of bolls. This reduction was commensurate with the reduced dry matter production from lower RUE g rather than light interception. A single waterlogging event during early squaring and five events throughout growth of the same cumulative duration gave the same impact on lint yield. However, when the single event was imposed at peak green bolls, it had no significant effect on yield. No impact of waterlogging on fibre quality was detected in any of the experiments.