Identifying Mechanisms of Putative Drought Tolerance in New Cotton and Soybean Genotypes Under Rainfed Field Conditions

New drought-tolerant row crop germplasm may help reduce risk under drought conditions in the southeastern U.S., but how these genotypes adapt to drought is poorly understood. This study examined how new genotypes of cotton and soybean with putative drought tolerance altered physiological and morphological characteristics in response to moisture stress compared to commonly used genotypes. Plant and soil-water responses were compared among two cotton genotypes, “DP2123 B3XF” (putatively drought-tolerant) and “DP1840 B3XF” (non-drought-tolerant), and two soybean genotypes, “N7006” (putatively drought-tolerant) and “Stonewall” (non-drought-tolerant). Soil volumetric water content and electrical conductivity were measured under each genotype at depths of 15, 30, and 45 cm from June to September, coupled with monthly measurements of leaf water potential, leaf size, and end-of-season yield. Results indicated that DP2123 consistently used less soil water at the 30 cm rooting depth, experienced less moisture stress, and produced heavier seed than the non-drought-tolerant DP1840 while maintaining similar lint yields. For soybean, N7006 did not alter soil water content, but produced smaller leaves and fewer beans per pod while yielding similarly to the non-drought-tolerant Stonewall. These findings indicated that cotton adapted to drought by reducing water use, while soybean altered yield components rather than water uptake.