Abstract
An experiment was conducted to investigate the early growth of warmseason grasses under the light competitive condition with the preceding cool-season grasses into which the former species were undersown. Three warm-season grasses, Kazungula setaria (Setaria anceps cv. Kazungula, abbreviated as S), Green panic (Panicum maximum var. trichoglume cv. Petrie, abbr. P), and Dallisgrass (Paspalum dilatatum, abbr. D) were grown under shaded condition of 22% (d-treatm.) and full daylight (1-treatm.). With regard to S, 38% (m-treatm.) was added. The shading treatments were applied from 29 Aug. 1974 when the grasses were sown in pots. Their growth were measured three times at intervals of a week. Results are summarized as follows, 1) The growth of each species was retarded by the shading treatment except the plant height (Table 1). The total plant dry weight under d-treatm. was 10% of 1-treatm.. The reduction was heavier in D comparing to P and S. 2) Under d-treatm., the total plant dry weight of S and D species was reduced to 4% of 1-treatm., and 6% in P, but under m-treatm. S maintained 30% after 40 days of treatment (Fig. 1). 3) In S, C/F ratio was increased with the growth under each light condition, and in P, it showed a slight increase in contrast with D, which showed reduction under d-treatm. (Fig. 2). 4) The reduction of RGR by the shading was small in P and S (Table 2). In case of P, increase of LAR by means of thinner leaf blade seemed to compensate the reduction of NAR under shade, and S gained the same compensation by raised distribution of produced dry matter into leaf portion. 5) Many factors must be taken into consideration to select suited species of warmseason grasses to undersowing. But above results show that P and S are thought to be superior from the view point of maintaining better dry matter production even in the shaded condition though these two were different in the mode of adaptation for the shade.
