Temperatures for seedling emergence of tropical perennial grasses

A growth-cabinet study was conducted to determine the optimum temperature range for seedling emergence of seven tropical grasses commonly sown in the frost-prone, summer-dominant rainfall region of inland northern New South Wales. The grasses were Bothriochloa bladhii subsp. glabra (forest bluegrass) cv. Swann, Bothriochloa insculpta (creeping bluegrass) cv. Bisset, Chloris gayana (Rhodes grass) cv. Katambora, Digitaria eriantha (digit grass) cv. Premier, Panicum coloratum var. makarikariense (makarikari grass) cv. Bambatsi, and Megathyrsus maximus (panic) cvv. Gatton and Megamax 059. Six constant temperatures were used, ranging from 10 degrees C to 35 degrees C in 5 degrees C increments. Katambora Rhodes grass was the only grass to emerge at 10 degrees C; seedlings of all grasses emerged at temperatures > 10 degrees C. Optimal temperature range for emergence varied between species, falling into three groups: low (Bisset creeping bluegrass 16 - 22 degrees C); intermediate (Premier digit grass 21 - 32 degrees C, Swann forest bluegrass 23 - 31 degrees C, Megamax 059 panic 23 - 35 degrees C, Gatton panic 24 - 32 degrees C); and high (Bambatsi makarikari grass 24 - 35 degrees C, Katambora Rhodes grass 24 - 35 degrees C). The temperature range at which 50% of optimum emergence occurred was 12 - 14 degrees C for Katambora Rhodes grass, Bisset creeping blue and Premier digit, and 17 - 18 degrees C for the panic grasses, Swann forest bluegrass and Bambatsi makarikari grass. These temperatures provide options for sowing earlier in spring or later in summer-autumn and may assist development of sowing time options in new environments and provide insight into competition between species.