This study was undertaken to investigate the effects of the nitrogen forms on the plant growth, dowering and tuberous roots development in dahlia, under the conditions of three kinds of soil, namely sandy loam, sandy clay loam, and loam.
1. Ammonium sulfate promoted much the plant growth of dahlia and next were ammonium nitrate and urea in order. However, effects of ammonium nitrate was promoted as clay contents increased, so that it was similar to the plot of ammonium sulfate. Urea was less effective in each textual class of soils. The effects of fertilizer in general was revealed good results as the contents of clay increase.
2. In ammonium nitrate plot, yields of tuber were higher, while lower in urea plot, these was not found the same tendency by different soil conditions but yields of large tubers were increased in ammonium nitrate plot and it was decreased as clay contents were high.
3. Flowering date was similar in ammonium sulfate and ammonium nitrate plots and it was late in urea plot. This was not found as clay contents increased. The number of flowers was lower also in urea plot and in the havier soil also.
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