Effects of deficit irrigation on photosynthesis, photosynthate allocation, and water use efficiency of sugar beet

Deficit irrigation is commonly used to improve crop yields in arid land. Our study evaluated the response of physiology and yield of sugar beet (Beta vulgaris L. cv. Beta 356) to deficit irrigation via applying three irrigation treatments (30%, 50%, and 70% of field capacity (FC)) during canopy development stage. The results showed that deficit irrigation significantly increased the dry matter of sugar beet taproot. The dry matter for the moderate deficit irrigation treatment (50% FC) was more than that for the severe deficit irrigation treatment (30% FC). Only severe deficit irrigation treatment significantly reduced the yield of sugar beet. Photosynthetic parameters of sugar beet reduced with water deficit increasing. However, the moderate deficit irrigation treatment significantly increased instantaneous water use efficiency (WUEi) and water use efficiency for yield (WUEy). Leaf Delta C-13 was negatively correlated with the WUEy of sugar beet. After rehydration, more photosynthate was allocated to taproot for the moderate deficit irrigation treatment, which increased the yield, while more photosynthate was allocated to the aboveground part for the severe deficit irrigation treatment. Short-term gas exchange measurement was used to indicate the dry matter accumulation, and the result was used to formulate deficit irrigation management strategies for sugar beet.