暖地型一年生マメ科牧草

A mixed culture of tropical legume, phasey bean (Macroptilium lathyroides), Pb, with tropical annual grass was evaluated by the dry matter yield, nutritive value and competitive relation. The four grass species used were green panic (Panicum maximum var. trichoglume), Gp, Rhodes grass (Chloris gayana), Rg, colored guineagrass (Panicum coloratum), Cg, and setaria (Setaria anceps cv. Kazungula), Se. Two nitrogen levels (1 and 2kgN/a; LN and HN respectively) were applied three times in equal dressing at sowing and after two cuttings. 1) In LN treatment dry matter yield of Pb pure culture was higher than those of grass pure cultures, but lower in HN treatment. Four mixed cultures with Pb out-yielded respective grass pure cultures in dry matter yield irrespective of the applied N levels. The mixed cultures with Rg or Gp showed higher dry matter yield comparing with Cg or Se. Pb yields in LN mixed cultures occupied over 50 percent in total yield, but ranged between 17 and 31 percent in HN treatment. 2) Increases in nitrogen percent and in vitro dry matter digestibility of respective grasses were observed in mixed cultures and on high nitrogen application in the first cut, but not in regrowths. 3) The mixed cultures with Pb out-yielded nitrogen and digestible dry matter yields in respective grass pure culture irrespective of applied N levels. The order of increasing nitrogen and digestible dry matter yields was arranged in Gp mix≧Rg mix>Cg mix>Se mix. 4) RYT of the respective mixed cultures in both N levels of regrowths were over 1.0, which indicated that mixed culture utilized nitrogen efficiently. Grass species in mixed cultures became dominant in high N application, however Rg strongly suppressed the growth of Pb in mixed culture. It is suggested that Gp is suitable for mixed culture with Pb for higher dry matter and nutritive yields as the effect of mixture, and smaller suppression of the growth of Pb comparing with the other grass species.