2012 Volume 81 Issue 4 Pages 441-448
To investigate the effects of desalinization of the field caused by the March 2011 Tsunami on rice growth, we grew rice cultivar ‘Akitakomachi’ at six tunami-covered field spots in Iwate Prefecture, which were desalinized to a level below a criterion of 0.6 mS cm-1 EC, and examined their growth. Besides this field experiment, the rice seedlings grown in Iwate University campus were transplanted to pots filled with the culture soil on the market, and grown at the six desalinized fields (pot expt 1). In addition, another group of the same seedlings were transplanted to the pots filled with the soil from either one of the six desalinized fields and grown in Iwate University campus (pot expt 2). The dry weight at the flowering stage of the plants in the field varied greatly with the spot from 23 to 52 g plant-1, and was closely correlated with that in pot expt 2, but not with that in pot expt 1. However, the dry weight was not significantly correlated with the electrical conductivity (EC) of the soil and surface water, which confirmed the effectiveness of the criterion of desalinization. To evaluate the interactive effects of soil salinity with air temperature on rice vegetative growth, we grew rice plants under two temperature conditions (20.9 and 25.4°C) and six NaCl salinity conditions (0.1∼7.3 mScm-1EC). Leaf transpiration, which was higher at a high temperature than at a low temperature, was significantly reduced by high salinity. High salinity suppressed the vegetative growth and decreased dry weight at 0.8∼2.3 mScm-1EC at a high temperature, but not at less than 2.3 mScm-1EC at a low temperature. These experiments suggested that the criteria for desalinizing soil, 0.6 mScm-1EC, can be alleviated in cooler climate regions.
