Response of twelve soybean cultivars to water deficit in a Cerrados Dark-Red Latosol of the Federal District. I. Yield, leaf area and root development

Abstract

During the dry season of 1979 and 1980, the response of twelve soybean cultivars to water deficit was studied at the Cerrados Research Center, Planaltina, DF, Brazil. The plants were exposed to a dry spell at flowering stage. During 1979, irrigation of the cultivars was suspended for 27 days (128 mm tank A evaporation) and during 1980 irrigation was suspended for 36 days (245.8 mm tank A evaporation). Yield response indicates that the cultivars can be classified into three groups. a) Resistant to water stress; b) intermediate and c) non resistant. Best results were obtained with cultivars Doko and Cristalina. During 1979 and 1980, under permanent irrigation, Doko cv. Yields were 4,194 and 3,079 kg/ha, respectively; and under water stress, yields were 2,452 and 1,482 kg/ha, respectively. During 1980, Cristalina cv. yields were 2,254 kg/ha under permanent irrigation and 1,497 kg/ha under water stress conditions. Leaf area index (LAI) was greatly reduced by water stress but it was not clearly associated to cultivar response. 75 to 85% of soybean roots were distributed in the upper 20 cm of soil profile. Stress resistant cultivars showed higher root density in the upper 20 cm of the soil profile than the stress non-resistant cultivars. Root density showed by cultivars with or without permanent irrigation was not different, which suggests that this parameter is not sensible enough to study plant response to phe phenomena.