Response of Soybean Genotypes to Different Irrigation Regimes in a Humid Region.

Several studies have demonstrated that soybean yield for non-humid regions increases with irrigation. The objective of this study was to determine the response of four soybean genotypes to different irrigation regimes for a humid region. A field experiment consisting of four soybean varieties that represented maturity groups V, VI, VII, and VIII was conducted during the 2006 growing season at the Bledsoe Research Farm in Williamson, Georgia, USA. The seeds were planted on May 30, 2006 and three irrigation regimes including rainfed, irrigation starting at anthesis, and full season irrigation were established. The field was 0.58-ha in size and consisted of a completely randomized block design with a split-plot array and 4 replicates. The irrigation regimes were the main treatments and the soybean varieties were the sub-treatments. Irrigation was applied with a lateral sprinkler system. Growth analysis samples, including biomass, canopy height as well as leaf area index (LAI), were taken every 12 days from a 1-m row length.  The PROC GLIMMIX of SAS was used to perform ANOVA. The variables analyzed included LAI, canopy height, aboveground biomass of the plant and its components, and seed yield. There were significant differences (p < 0.05) between irrigation regimes for all variables analyzed as well as for all variables within genotypes, except for LAI. However, there were no significant differences between the interaction of irrigation regime and plant components within genotypes. The LS-Means, with irrigation regimes and replicates as random effect, showed that maturity group VIII performed and yielded better than the other genotypes, demonstrating the importance of MG under irrigated soybean crop management.