Interactive effects of elevated CO2, temperature and extreme weather events on soil nitrogen and cotton productivity indicate increased variability of cotton production under future climate regimes

Increased atmospheric concentration of CO2 (C-E) and temperature (T-E), and extreme weather events, are predicted to affect future agricultural production. However, our knowledge regarding interactions between these factors is limited, thus potentially underestimating the impact of future climates on agricultural productivity. Using a large glasshouse experiment, we examined how flooding and drought events affected cotton productivity and soil nitrogen availability when grown in the current and future CO2 and temperature regimes, and whether these responses differed between different soils. In the absence of extreme weather events, season-long T-E, and C-E to a lesser extent, significantly increased cotton yield. Flooding induced immediate physiological responses in cotton and soil nitrogen losses, leading to reduced vegetative growth and a significant yield loss under all climate regimes but particularly at T-E. Drought greatly reduced physiological processes, growth and yield under all climate regimes and resulted in a large amount of residual nitrogen in the soil, particularly at T-E. There were also small but significant differences between the two soils in some responses to flooding and drought under the current and future climate regimes. Our results demonstrated that T-E greatly increased yield in the absence of extreme weather events, however, it generated greater yield reduction following flooding and drought events, indicating that inter-annual variability in yield is likely to increase under more extreme future climates. Contrasting consequences for soil nitrogen also suggest that adaptive nutrient management will become increasingly important to secure the resilience of agricultural production under future climates.