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Abstract
The objective of this research was to quantify the relative yield loss attributable to Intercepted Photosynthetically Active Radiation (IPAR), Radiation Use Efficiency (RUE) and Harvest Index (HI) for cotton grown under three distinct irrigation treatments in 2018 and 2019. The results showed that ΨPD remained relatively high in both seasons and was rarely affected by irrigation treatment. A significant reduction in yield of 318 kg ha-1 was observed for over-irrigated treatments (which were comparable to the control) relative to the dryland treatment, despite irrigated plots producing higher biomass. Any positive effects of IPAR and RUE on lint yield due to excess irrigation were substantially offset by large declines in HI in irrigated treatments relative to the dryland. We conclude that HI was the dominant driver of yield loss due to excess irrigation, and our observations illustrate a need to refine irrigation management practices to maximize productivity and water use efficiency.