Crop Water Stress Index (CWSI) as an Indicator of Water Stress and Yield Performance among Cotton Cultivars

Field experiments were conducted in Seville (SW Spain) on a sandy loam soil (Typic Xerofluvent) to investigate the usefulness of CWSI in screening cotton genotypes for drought resistance and yield characteristics. Non-water-stressed baseline equations were determined in 1993 and 1994 by conducting a diurnal study of a well watered crop. Seventeen upland cotton genotypes were evaluated in 1994 in randomized complete blocks with four replications. Eight furrow irrigations were applied from June 8 to August 23 with a total of 800-900 mm of H2O applied. Crop Water Stress Index (CWSI) was quantified in seven dates. Variance analysis showed that dates and genotypes were highly significant for seasonal CWSI ranging from 0.38 for Acala Germain 510 to 0.59 for La Niña. Seed cotton yield was negative correlated to mean seasonal CWSI (r = -0.28). Seed cotton yields ranged from 4658 kg ha-1 for Stoneville 324 to 5723 for La Chata (a Spanish cultivar). CWSI revealed a good water status for some cultivars with low values in this characteristic but it was not a determining factor in the performance of cultivars under well-watered conditions. CWSI corroborates the drought tolerance of some Spanish genotypes such as Maria del Mar and could be a good tool in evaluating genotypic drought tolerance if a low seasonal CWSI is combined with high yields under well watered conditions.