Fertilizer effects of slag on fruit trees growing on volcanic-ash soil. II

(1) Tree growth and nutrient content of leaves as related to the soil reaction were observed with one year old trees of apple, grape and Japanese pear planted in pots with volcanic-ash soil. (2) For an adjustment of soil reaction, ground limestone and slag were used respectively, though the latter contained silica and magnesia beside lime. (3) In every species, tree growth was much promoted by an addition of either these two lime fertilizers. In apples and grapes, the effect of slag was more striking than that of limestone, especially the tendency being conspicuous in apples, while in pears no distinct difference was found between the two fertilizers. (4) As a result of leaf analysis, N content of leaves decreased with an increase of slag supplied. P content of leaves increased slightly in accordance with an increased application of limestone and of slag. However, no relation existed between the K content of leaves and the amount of the lime fertilizers added. The content of Ca, Mg and SiO2 was closely related to the amount of limestone and of silica-slag supplied, especially Ca to the limestone, and Mg and SiO2 to the slag. (5) Finally it is noticeable that growth of apple trees was correlated intensively with the content of Mg and SiO2 in leaves. And it might be a reason why slag was much superior to limestone as a fertilizer for apples planted in the volcanic-ash soil.