Mechanism of Wind Injury on Tobacco PlaLnts : III. On the relationship between stalk strength and wiater content

Abstract

In the previous paper, it was found that the physical properties of the stalk were greatly different according to the growth stage and variety to tobacco. On the other hand, it was known that the root lodging and stalk breakage were signiftcantly increased when the weather was wet and the ground was loose. Based on those results, the present experiments were carried out to reveal the relationship between stalk strength and water content in 1964-1966 at the Hatano Tobacco Experiment Station. Five varieties grown under normal cultural practics were selected for this study. The stalks were cut at the ground level and used as samples after removing all of the leaves. The water content of stalks and the variation of soil moisture were measured on three plots described below. One third of the samples were measured as soon as possible after the cutting and one third were 2 days after. In the remained sample the bottom of the stalks were soaked in water for 2 days and then the samples were used for experiment. The procedure of the measurement was the same with that describctd in the previous report. Results obtained are as follows. 1) The water content of the stalk was found to be different according to the growth stage, especially in the harvesting stage, it was much lower than in the early growing stage. The water content of the stalk in rainy day was higher than in clear day. 2) The water content of the stalk was different by stalk position and in the top of the stalk, it was higher than in the base. 3) The bending stress showed different values with tlle different water content through out all stages and some differences in the stalk breakage were observed in connection with the water content of the stalk. 4) From these results that the stalk breakage is increased when the weather is wet and loose, the auther suggested a method to prevent the damages of stalk breakage by film mulching practice.