Six cotton cultivars were evaluated in the field for differences in root and shoot traits, canopy temperature, yield and earliness under irrigated and non-irrigated conditions. Four of the cultivars were from the multi-adversity resistance (MAR) program, and the other two Deltapine 41 and Paymaster 303, were non-MAR cultivars. Root and shoot traits were measured at the squaring stage prior to irrigation and at plant maturity. An infrared thermometer was used to measure canopy temperatures over a 4-week period during peak flowering. The irrigated treatment received five supplemental irrigations of approximately 3-acre inches each from June 30 to July 30. The non-irrigated treatment received less than 0.05 inches of rainfall during the supplemental irrigation period.