Recently published information on cotton agronomic and photosynthetic component responses to nitrogen (N) application rate is limited for the southeastern US. This experiment was conducted to 1) evaluate cotton yield, fiber quality, growth, and maturity responses to N application rate and 2) quantify associations between photosynthetic component processes and N-induced variation in net photosynthesis. A two-year field experiment was conducted during the 2015 and 2016 growing seasons at a field site in Tifton, GA and evaluated cotton agronomic and physiological response to six N fertilizer application rates ranging from 0 to 168 kg N ha⁻¹. Cotton lint yield was 42–51% lower in 0 N treatments than all other fertilized treatments in both years of the study, and N rates that substantially limited yield decreased final plant height, reduced mainstem node development, and substantially hastened maturity. Date of cutout ranged from 73 to 91 DAP for all N rates and years of the study. Photosynthetic rates were also responsive to N rate on later sample dates (July and August) for both growing seasons. Although declines in chlorophyll content, specific leaf nitrogen, and stomatal conductance were observed for low N plants in some instances, none of these parameters were strongly associated with net photosynthesis overall. In contrast, light-dependent electron transport rate (ETR) was strongly correlated with N-induced variation in net photosynthesis. Estimates of ETR may need to be included along with SLN estimates in future efforts to scale from leaf to canopy level photosynthetic performance in cotton.

美国东南部最近发表的关于棉花农艺和光合成分对氮 (N) 施用率的响应的信息有限。本实验旨在 1) 评估棉花产量、纤维质量、生长和成熟度对施氮量的响应，2) 量化光合成分过程与氮诱导的净光合作用变化之间的关联。在 2015 年和 2016 年的生长季节，在佐治亚州蒂夫顿的一个田间地点进行了为期两年的田间试验，并评估了棉花对六种施氮肥的农艺和生理响应，范围从 0 到 168 kg N ha ^-1. 在研究的两年中，0 N 处理的棉花皮棉产量比所有其他施肥处理低 42-51%，并且显着限制产量的 N 比率降低了最终植物高度，减少了主茎节发育，并显着加速了成熟。对于所有 N 率和研究年份，截止日期范围为 73 至 91 DAP。在两个生长季节的较晚采样日期（7 月和 8 月），光合速率也对 N 速率有响应。尽管在某些情况下观察到低氮植物的叶绿素含量、比叶氮和气孔导度下降，但这些参数都与总体净光合作用没有密切关联。相比之下，光依赖电子传输速率 (ETR) 与净光合作用中 N 诱导的变化密切相关。