Abstract
Five different irrigation water from 200 to 2, 500μS/cm electric conductivities were prepared through diluting sea water with under ground water. They were supplied into the respective blocks of rice plant every 2 to 3 days under the condition of percolation during the irrigation season. The blocks were placed in a green house and the relations between the growth of rice plants and the irrigation water were studied. The results are as follows.
1) The rice plant in the block getting irrigation water of EC value 2, 500μS/cm was damaged just after transplant in spite of the opitimum percolation which is 17 mm per day.
2) Etiolation was observed on the plant in the block of EC value 1, 900μS/cm immediatly after mid?summer drainage. The maximum ratio of etiolation judged by the number of plant stems was around 60% at the booting stage, but after that, this phenomenon decreased gradually and disappeared at the milk ripe stage. The average percolation rate in this period was 60 mm per day, which was a good condition for desalting soil layer. This shows that the development and the function of plant root after mid-summer drainage are great factors to the control of outbreak of etiolation. On the other hand, in the blocks under EC value 1, 400μS/cm, damages did not occur and the rice plants grew smoothly.
3) The salinity desalted in the soil layer by supplied water was around 250μS/cm in EC value in the average during irrigation season, but it varied due to the percolation rate.
