Abstract
Yield trials of three guineagrass cultivars ('Natsukaze', 'Natsuyutaka' and 'Gatton'), three experimental lines ('Kyushu No. 3', 'Tift PM39' and 'Tilt PM 41'), one green panic cultivar ('Petrie') and two rhodesgrass cultivars ('Katambora' and 'Hatsunatsu') were conducted on Ishigaki Island, Okinawa Prefecture, Japan. Among them, 'Natsuyutaka' was most promising of the guineagrass cultivars and lines studied for both 3 years and 7 years because it is extremely productive and drought tolerant. 'Tift PM39' and 'Gatton' also showed promise based on their productivity and persistence. 'Kyushu No. 3' would be well suited to grazing because of its winter productivity and regrowth. Although 'Natsukaze' gave the highest dry matter yield in the first year, it was less persistent than the other cultivars. Two rhodesgrass cultivars and 'Petrie' green panic were less persistent than the guineagrasses. Flowering patterns suggest that 'Natsukaze', 'Natsuyutaka' and 'Katambora' may be more sensitive to photoperiod than the other cultivars and lines. 'Natsuyutaka' and other guineagrass cultivars could be used for overseeding or reestablishment of degraded rhodesgrass pastures in Okinawa. It will be very difficult to obtain a large amount of 'Natsuyutaka' seed on Ishigaki Island because it produces fewer seed heads than the other cultivars and lines, and flowers strongly during the wet September to January period.
