LAUSR

Water deficit is generally thought to negatively impact crop yields, including grain sorghum (Sorghum bicolor L.), but a small body of literature reports changes in crop physiology and growth in plants with short-term imposition of water deficit during vegetative development that could lead to increased yield. In a replicated and repeated pot experiment in which water deficit was imposed for 10-day periods in grain sorghum plants that were otherwise well-watered, we tested the hypothesis that relatively severe, short-term water deficit imposed during early vegetative development could enhance grain sorghum yield. The results showed that severe water deficit (~30% of control ET) imposed during two vegetative periods enhanced grain yield compared to continuously well-watered plants by 21% (p = .0356). Grain yield was correlated with average grain weight, grain number per head and shoot-to-root ratio. Yield enhancement was associated with a substantial shift in resource partitioning, as water deficit reduced root mass (p = .0032), stem/leaf mass (p < .0001) and total biomass (p = .0005), resulting in a 60% increase in harvest index. Imposition of water stress during vegetative growth in sorghum can increase grain yield.