Effects of elevated CO2 and warmer temperature on early season field-grown cotton in high-input systems

Changes in temperature and CO₂ under the scenarios of climate change present a challenge to crop production and may have significant impacts on the yield of cotton (Gossypium hirsutum L.) crops. The aims of this study were to (a) investigate the use of novel chambers to evaluate the impacts of climate change, specifically warmer temperatures combined with elevated atmospheric CO₂ concentration ([CO₂]), on field-grown plants; (b) compare the combined effects of elevated [CO₂] and temperature on leaf-level photosynthetic rate and plant biomass; and (c) assess the effects of elevated [CO₂] and warmer temperature on soil water content and leaf-level water-use efficiency (A_sat/E). Canopy evapotranspiration and assimilation (CETA) chambers were used to elevate [CO₂] in the field over two consecutive seasons, but also generated higher air temperatures (on average 2–4 °C warmer) at ambient (C_A: 400 μl L⁻¹) and elevated [CO₂] (C_E: 650 μl L⁻¹) from ∼44 days after planting (DAP) until 72 DAP. Elevated [CO₂] increased early stage vegetative biomass by 34–68% in well-watered, field-grown cotton growing at warmer temperatures. Despite increased A_sat/E with C_E, there were minimal changes in leaf-level biochemistry (estimated from gas exchange) and volumetric soil water content (VSWC) over the 28 d period, potentially the result of the combination of greater biomass and improved A_sat/E. We observed increased early season crop growth of cotton grown in a changing climate; however, studies are needed to assess the effects of elevated CO₂ and temperature on cotton production over a full growing season in the field.