The copper-poisoned soils were studied to clarify the question introduced from the previous report. First of all, the copper contents of the soils and the rice plants in the paddylands, growing favorably or poorly, were measured in connection with the difference of the growth. The soils were measured with the total copper contents and the available ones under the paddyland condition. The results obtained were comparatively investigated by the experiment of the younger rice plant cultivation. Secondly, the effects of the drying processes of the paddyland soils on the available copper contents were investigated.
The results were as follows:
(1) The available copper content under the paddyland condition was 181.8 ppm in the paddyland soil, growing the rice plant poorly, and was more than 4 times, in comparison with that of the paddyland soil, growing the rice plant favorably. The difference of the growth was more obviously shown by the available copper content than by the total one.
(2) The copper content of the rice plant of the poor growth was as same as that of the favorable growth.
(3) According to the experiment of the younger rice plant cultivation, the plants were poisoned by the existence of the available copper of more than 100 ppm under the paddyland condition. The copper contents of the plants were parallel with the quanties of the copper application.
(4) The available copper contents were increased with the drying processes of the paddyland soils, distributed in the copper-poisoned area. The conditions of the moisture and the temperature had the influences on the available copper contents.