1956 Volume 25 Issue 1 Pages 59-68
In the present paper, the results of the experi-ments on the relation between oxidation-reduction potentials, Fe.. and H25 contents in soils, and the submersion tolerance or excess-moisture injury of the fruit-tree roots are reported with special reference to fig, peach, pear, apple, persimmon and grape. The results are summarized as follows.
1. The growth of fruit-tree shoots were stopped by excess-moisture or water-lodging in the soils having following values of Eh6
Fig 360_??_370m. v.
Peach 330_??_350m. v.
Pear and Apple 260_??_280m. v.
Persimmon 200m. v.
Grape 170_??_180m. v.
Shoot growths of pear, apple, persimmon and grape were inhibited gradually from the neigh-bourhood of ca. 300m. v.
2. Fe..-formation in soils increased as the oxi-dation-reduction potentials failed, and the amount of Fe.. extracted by HCl (pH 3) solution was ca. 20mg at 300m. v., ca. 30mg at 200m. v. and 60_??_70mg at 100m. v., per 100g. dry soil. There-fore, the root system of fig or peach was impeded mainly by oxygen-deficiency before Fe.. was formed abundantly in soil. On the other hand, the impediment of root system in the case of pear or apple was derived from a large amount of Fe.. formed by remarkable reduction in soils, and moreover, when approximately 30 mg Fe..
was formed in soils on persimmon or grape.
3. When the soils were water-lodged, the higher organic matter content in soil, the more rapid Eh falling and more the amounts of Fe.. and HsS formed. Accordingly, the more high organic matter content in soil, the more remarkable the injury of root system of fruittree caused by excess-moisture.
4. Fig and peach were susceptible, pear was middle and grape and persimmon were resistant. Parallelism between resistance of root system to Fe.. and H2S, and submersion tolerance of root was found. And it was suggested that the differ-ence of resistance to excess-moisture injury was caused by the difference of oxidation power of root towards the exterior.