Abstract
Two experiments were carried out with dwarf grain sorghum (Sorghum vvlgure Pers.), using hybrid seed from U.S.A. in 1968. One of the purposes was to examine the yield abilities and related characters of 12 varieties, and the other was to evaluate the effects of 7 plant densities combined with 3 nitrogen levels on the yield as well as yield component with one variety. The results are as follows.
1. Yield of varieties varied considerably between 70kg/a and 38kg/a.
2. High yielding varieties showed the tendency to have the following characters; thick and short stalk, much joints, broad but short leaf and loose type panicle.
3. Typhoon damaged leaves but caused neither lodging nor shedding of grain.
4. Both dry weather and low temperature retarded initial growth rate, resulting in delay of flower differentiation.
5. Yield per unit area increased with higher plant density and the peak was at 2, 000 plants /10 a in non nitrogen plot, while at 4, 000 plants /10 a in both nitrogen plots, thereafter slowly reduction of yield occured with denser populations.
6. Higher nitrogen level favoured to the grain porduotion as well as numbers of grains per year at any plant density.
7. Length of stalk, ear and recondary rachis-branch were all hardly affected by nitrogen levels but strongly influenced by plant density; in the positive direction on the former, contrary in the negative derection on the latter two.
