Studies on the Relation between the Tolerance of Crops to Soil Acidity and That to Low pH : (14) The effects of fertilization on acidic soils with different pH values

Abstract

Soils with different degrees of acidity were prepared by adding varying amounts of lime to "Kuroboku" (volcanic ash soil rich in humus). The effects of different kinds of fertilizers on the growth of Italian ryegrass and milk vetch on these acidic soils were compared. Test plots established for this experiment were: standard, calcium cyanamide, phosphate deficient, potassium deficient and magnesium deficient ones. The test results are summarized as follows: (1) As the rate of germination of milk vetch showed a close correlation with the early-or late-start in germination of seeds and the plant growth in the early stage, such factors as soil acidity and kinds of fertilizers which have bearings on the plant growth are thought to have acted from the start in germination of seeds. However, th toxic effect of calcium cyanamide on milk vetch was greater in times of germination of seeds than in the early plant growth stage. In cace of Italian ryegrass, it showed little correlation between the rate of germination of seeds and the plant growth in the early stage. (2) In both cases of milk vetch and Italian ryegrass, the plant growth in the early stage showed a high correlation with the yields, but it showed poorer plant growth in the later stage of milk vetch in the cases of strongly and weakly acidic plots. (3) Marked decreases in Y1 and activated aluminum were caused by the changes in soil pH. Namely, within the range of the pH (KCl) from 4.2 to 4.5, it showed great increases in the crop yields by the additional application of lime. Within the range of pH from 4.5 to 6.5, however, the yields of Italian ryegrass showed increases little by little by the liming, while the yield of milk vetch resulted is decreases. (4) Within the range of soil pH hi gher than 4.5, in the case of Italian ryegrass, the fertilizer effects of applications of phosphate, potassium and magnesium were greater than the raise in soil pH, and the applications of these fertilizers of optimum concentration gave particularly marked effects on the yield of milk vetch. (5) When calcium superphosphate was applied according to the conventional method to the layer at 5 cm under soil surface of strongly acidic soil (calcium- and phosphate- deficient soil), it showed greater effect by the deficiency in calcium than in phosphate.