Effect of Saline Water on Crop Water Potential and Transpiration Rate

At newly developed agricultural fields resulting from reclamation from the sea, productivities of crops are affected by salt remaining in the soil. Moreover, water below the drainage pipes having a high concentration of salt can possibly, through capillary action move upwards and damage crops. It is reported that root activity is affected by the salt when the concentration exceeds around 0.02 to 0.04 N, but threshold values are not clarified physiologically. Experiments to clarify the effect of salt on crop water extraction from soil by roots were conducted using broccoli grown in Masa sandy loam. Salt water concentrations of 0.0N, 0.05N, 0.1N, 0.2N were applied and water potential, transpiration, leaf temperature were measured under onstant light intensity. An SPAC model was developed to explain the interaction between crop water potential and soil water potential. It was found that the effect of salt on water absorption by roots began at around a 0.05N concentration and the roots stopped absorbing water at around a 0.2N concentration. At high salt concentrations, water potential in crop cells in the roots and the stems showed irregular distribution and the resulting transpiration showed abnormal conditions. This phenomenon concluded as a physiological breakdown caused by the high salt concentrations. Simulated water potentials in the crop from the roots to the tips of stems showed good agreement at a non-salt water condition, but at high concentrations of salt, the SPAC model could not be applied because of the unexpected physiological reaction of the crop to salt water.