Changes in Agronomic and Physiological Traits of Sugarcane Grown with Saline Irrigation Water

In Japan, the highest salt concentration in irrigation water for sugarcane cultivation has been reported to be above 2500 mg L-1, which may cause harmful effects to the crops; however, little information is available on the relationship between the salinity of irrigation water and sugarcane. To investigate its effects on agronomic and physiological traits, a Japanese cultivar, Saccharum spp cv. NiF8, was grown with 0, 200, 500, 1000, 2000, and 3000 mg NaCl L-1 under pot conditions. The treatments significantly lowered leaf area; however, NaCl levels up to 500 mg L-1 did not greatly reduce culm weight and juice sugar concentration. These traits were impaired when the tested cultivar was grown with 1000 mg NaCl L-1 or higher, indicating that salt concentration is desired to be lower than 1000 mg L-1. CO2 assimilation rate was inhibited mainly due to stomatal closure caused by salt stress. The treatments significantly altered Na+, Cl-, and K+ concentrations in juice but not those in leaf, suggesting that juice analysis is an effective method to estimate its salinization status. Culm weight and juice sugar concentration were severely affected as juice conductivity exceeded 900 mS m(-1); thereby, sugarcane plants of NiF8 possessing conductivity above this level could be considered salt-stressed where water salinity is a concern.