Abstract
The change of organic acid components of several grasses was investigated in spring of 1975 on the swards of pure stand which had been kept for 6 years with 2 levels of fertilizer supply (N-P_2O_5-K_2O ; 1-1-1 and 4-4-4kg/a) and 11-13 cuts in each year, respectively. Species used, included Kentucky bluegrass, orchardgrass, perennial ryegrass, red top, and tall fescue which were widely distributed on pasture in Japan. The swards were treated with 2 levels of fertilizer supply (N-P_2O_5-K_2O ; 1/4-1/4=1/4 and 1-1-1kg/a) on April 25 after trimming and sampling had been taken onwards. The same procedure as previous report was adopted for treatment and analyses of the sample. The results obtained were as follows: 1) The marked differences between species were recognized in contents of malic, quinic, and t-aconitic acids at the first cut (May, 10th) after fertilizer application. Particularly, t-aconitic acid was remarkably high in only red top, but there was little difference in content of citric acid between species. 2) Higher rate of fertilizer supply caused higher content of malic acid in both orchardgrass and perennial ryegrass, and higher content of t-aconitic acid in red top. The effect, however, decreased to great extent at the second cut (May, 23rd) after fertilizer supply. 3) During advance of growth stage in spring, t-aconitic acid was not detected significantly in any species other than red top while the contents of citric acid were kept low in those species. 4) Different organic acid components were shown in each plant part of grasses in which it must be noted that t-aconitic acid in red top showed markedly higher content in its leaves. From above findings, it was concluded that further research should be made for the relation between red top and outbreak of grasstetany.
