Abstract
5 crop species were grown to know the most suitable pH value of soils for those plants modified by adding lime or nitro-lime to high-acidic volcanic ash soils of high cation exchange capacity and low base saturation. Results obtained are summarized as follows: (1) Germination and the following early growth were arrested comparatively little by soil scidity. Tolerant plants in their earlier stages of development seemed to be strongly influenced by N concentration and also quite susceptible to excessive Ca applied. (2) As the plants grew, the highest growth was seen in the plots of high pH values owing primarily to Al toxicity; this seems to be due to gradual acidification of soils by raising the intolerant plants to soil acidtiy and also possibly to the decreased susceptibility of the plants themselves to excessive Ca. (3) The highest yield of maize was gained at pH 5, and others at pH 6.4, however, as for sugar beet, yield could not be increased on soils of higher pH any more. These results show that the pH value giving the most promising yield on this soil seems to be those which are least susceptible to excessive Ca and also give least Al toxicity.
