Abstract
In the previous paper, we described that the nitrate accumulation related closely with the age of fodder turnip. The purpose of the present report was to examine the differences in nitrate accumulation among species or varieties of forage crops. For this reseach, culturing conditions were investigated by using Italian ryegrass as a test plant. And then, forage crops of 21 species and 44 varieties were grown with the same nutrient solution contained 100 ppm of nitrogen. The results obtained were as follows. 1. The contents of nitrate nitrogen in Italian ryegrass increased with the increasing of concentration of nitrate nitrogen in the culture solution. Especially, its contents increased almost linearly at any varieties, as the concentration of nitrate nitrogen in the medium was increased up to 100 ppm. 2. The contents of nitrate nitrogen in both the top and the root of Italian ryegrass were markedly high in the early stage of growth and decreased gradually with aging. 3. Growing in the nutrient solution contained 100 ppm of nitrate nitrogen, some differences of nitrate accumulation in plant among species or varieties was observed. The level of nitrate accumulation of each species decreased in following, order on the basis of their mean values. Grasses: orchard grass (17.71mg as nitrate nitrogen per 1 gram in dry matter)> timothy (16.99)>medow fescue (16.19)>kentucky blue grass (14.97)>rodesgrass (10.13)>Italian ryegrass (10.23)>bent grass (9.20) Legumes: white clover (17.27)>alsike clover (15.71)>red clover (13.81)>alfalfa (7.75)On the other hand, the varitation of nitrate contents in Italian ryegrass was markedly larger than those of orchard grass or timothy. 4. The contents of nitrate nitrogen in alfalfa at any time of repeated harvests were usually lower than those of Italian ryegrass, red clover and white clover. 5. The nitrate accumulation in leguminous forages were higher than might be expected. For example, 17.46mg as nitrate nitrogen per 1 gram in dry matter was observed in white clover.
