Studies on physical properties of soils in relation to fruit tree growth

Abstract

Since 1947 the effects of low oxygen concentration which suspend the top growth or dry to death upon the growth of peach, pear, persimmons and apple seedlings have been studied by regulating sealed pots except upper and bottom holes to keep the oxygen concentration within the alloted range. Continuously aerating system used in the present study, which can decrease oxygen level to less than 1 or 2% continuously. Top growth of peach seedlings was normal in about 7916 or more oxygen level and not so much less than that of check plots. When oxygen level decreased to less than 5%, growth of peach seedlings was remarkably decreased. Further decreasing to less than 2% oxygen level caused wilting to death. As continuous oxygen level less than 1% enongh to ceasing of shoots or roots growth of pear, persimmon or apple can not be obtained under the sealed pots which are regulated by aeration through upper or bottom holes, apparatus for continuous aerating system of prescribed oxygen level was used in this study. Almost none of growth difference, compared with check, was found under the current aerating of 5% oxygen. Ceasing of shoot growth was found in 2% oxygen aerating. Tops of apple and pear seedlings began to wilt in less than 1% oxygen analysed concentration about one week after treatment and began to die after about two weeks, whereas persimmon (D. Lotus LINN.) did not die but showed faded leaf colour or some defoliation only 35 days after treatment of the lowest concentration. Excavated persimmon roots showed comparatively normal development in lower oxygen concentration.