Grasses and herbivores evolved about the same time. Hyams (1971) believes that "Without the exceptional powers possessed by grasses to grow again after being eaten almost down to the roots, a large number of animal species, including nearly all farm animals could not have evolved." He says, "It is possible to argue that the astounding success of Homo sapiens as a species is ultimately due to the power possessed by grass to grow again after being eaten down by animals."
Grasses are cosmopolitan from the equator to the arctic circle. Wherever flowering plants will grow, grasses can be found. It is estimated that there are about 10,000 species of grasses in the world, grouped into 620 genera arranged in 25 tribes (Hubbard 1954). There are 173 genera found in South Africa, most of which are indigenous (Meredith 1955).
Grass tribes may be grouped as Panicoid grasses containing the tropical and subtropical species and Festacoid grasses containing the temperate species. The panicoid group contains most of the African grasses. The panicoid grasses (Bogdon 1977) fix carbon by the efficient C4 pathway of photosynthesis that has optimum temperatures of 30° to 40°C and optimum light intensities of 50 to 60 klx. The festucoid grasses use the C3 photosynthesis processes that optimizes at 15° to 20°C and 15 to 30 klx. With optimum light and temperature Panicoid grasses can fix 30 to 50 g dry matter m-2d-1 whereas Festucoid grasses can fix up to about 20 g dry matter m-2d-1. Panicoid grasses do not make use of this advantage under low temperatures and low light intensities.
Although bermudagrass originated in Africa, it is cosmopolitan today occurring in every tropical and temperate part of the world. Its seed producing ability and its woody stolons and rhizomes have made it a weed. When southern crops were grown with a man, a mule, and a plow, bermudagrass was the farmer's worst weed. Yet, it saved untold acres of soil from erosion and became the South's first and most widely grown pasture and turfgrass.
Bermudagrass is a highly variable species (Burton and Hanna 1985). One variant crossed with tall selected types from South Africa produced 5,000 hybrids, the best of which, after much testing became 'Coastal' bermudagrass, named for the Georgia Coastal Plain Experiment Station where it was bred. In numerous tests, 'Coastal' bermudagrass has yielded about twice as much as common bermudagrass. In a year with only half of the average rainfall, 'Coastal' yielded six times more than common. 'Coastal' bermudagrass crossed with a common bermudagrass from Berlin, Germany produced 'Tifton 44', the best of 3,500 F1 hybrids (Burton 1978). Because of its greater cold tolerance, 'Tifton 44' can be grown 160 km farther north than Coastal bermuda.
'Coastcross-1' bermudagrass, an F1 hybrid between 'Coastal' and a highly digestible bermudagrass from Kenya, yields no more dry matter but is 12% more digestible than 'Coastal' and gives 30 to 40% more average daily gains (ADGs) and liveweight gains (LWG) per unit area (Burton 1972). It is restricted to Florida and the tropics.
'Tifton 68', an F1 hybrid between PI 255450 and PI 293606 both from Kenya, is the most digestible bermudagrass in our collection of 500 introductions (Burton and Monson 1984). It is a hexaploid, 2n = 54.
'Callie' bermudagrass, a natural hybrid found in an old Soil Conservation Service grass nursery, yields well but lacks winterhardiness and is very susceptible to rust that reduces forage yield and digestibility.
'Tifton 78' bermudagrass, a hybrid between 'Tifton 44' and 'Callie', is immune to rust and is a little less winterhardy than 'Coastal' (Burton and Monson 1988). Compared with Coastal, it is taller, establishes easier, starts earlier in the spring and in a 3-year grazing test produced 36% more LWG/A. Fertilized with 168 kg/ha of N plus P and K, it annually produced 983 kg/ha of liveweight gain at a fertilizer cost of 11cents per kg of gain.
'Tifton 85' is a tall, coarse, dark green F1 hybrid between PI 290884 from South Africa and 'Tifton 68'. 'Tifton 85', 2n = 45, is sterile but its large stolons and rhizomes make vegetative propagation easy. In a three-year replicated grazing trial, 'Tifton 85' has produced 47% more liveweight gain than 'Tifton 78'. It will be released officially in 1992. It is a little less winter hardy than 'Tifton 78', but should survive most winters in Florida and the southern half of the gulf states.
Other vegetatively propagated bermudagrass cultivars include 'Grazer', 'Midland', 'Hardie', and 'Brazos'. 'Pasto Rico' and 'Tempre Verde', commercial seed propagated mixtures of common and a tall wild type, are inferior to 'Coastal' and soon revert to low yielding common bermudagrass.
Cynodon nlemfuensis Vandeyst usually called stargrass is taller and larger than C. dactylon (Harland 1976). Stargrass is highly variable, spreads by seed and stolons but lacks rhizomes. It is softer, more palatable and has a higher digestibility than common bermudagrass. Stargrasses usually contains prussic acid glucosides but reports of livestock poisoning are rare. It lacks winterhardiness and is limited to South Florida and South Texas.
Thus, napiergrass is established from stem cuttings or crown divisions. If cut only once a year, napiergrass can produce more dry matter per unit area than any other crop that can be grown in the deep south, but cutting it twice a year at Ona, Florida reduced annual yields 70% (Burton 1986). Napiergrass cut once a year will produce more dry matter per unit of N and other fertilizer nutrients removed than other biomass crops.
Blaser et al. (1955) conducted a number of management experiments from 1938 to 1944 with napiergrass in Florida. They found napiergrass inferior to maize and sorghum as a silage crop. Its coarse stems made it a very poor hay crop to cure and handle. Fertilized with 67 kg/ha of N plus adequate P and K and grazed rotationally, napiergrass maintained a stand for 3 years, provided 235 steer days, gave ADGs of 0.71 kg and produced LWG of 414 kg/ha per year. Dairy cows did well on napiergrass fertilized and managed in the same manner.
Napiergrass breeding begun in 1936 produced the eyespot immune high-yielding 'Merkeron', the best of many hybrids between outstanding tall, selection No. 1 and a very leafy dwarf No. 208 (Burton 1990). A selfed progeny of 'Merkeron' contained a number of dwarfs, the best of which has been released in Florida as 'Mott' (Sollenberger et al. 1988).
|Potential future useu|
|Scientific name||Common name||Type of growthz||Height (m)||Reproduction methody||Adaptationx||Plantedw||Genetic improvementv||World||USA|
|Andropogon gayanus Kunth||Gamba||B||1-3||S?||WDtCs||SV||L||1||5|
|Brachiaria decumbens Stapf.||Surinam||SfS||0.3-0.6||A||WCs||VS||O||3||5|
|Brachiaria mutica (Forsk.) Stapf.||Para||SfS||1-2||A?||NDsCs||V||O||1||4|
|Cenchrus ciliaris L.||Buffel||BR||1-1.5||A||WDtCs||S||M||1||2|
|Chloris gayana Kunth.||Rhodes||SfS||1-2||S||WDtCt||S||M||2||4|
|Cynodon dactylon (L.) Pers.||Bermuda||SfSR||0.2-0.7||S||WDtCt||VS||M||1||1|
|Cynodon nlemfuensis Vanderyst||Star||SfS||0.3-0.9||S||WDtCs||V||S||2||2|
|Digitaria decumbens Stent||Pangola||SfS||0.4-0.8||V||WDtCs||V||O||1||2|
|Eragrostis curvula (Schrad.) Nees||Weeping love||B||0.4-1.0||A||WDtCt||S||S||1 2|
|Hyparrhenia rufa (Nees) Stapf||Jaragua||B||1-2||S||WDtCs||S||L||3||4|
|Melinis minutiflora Beauv.||Molasses||B||0.6-1.0||S||WDtCs||S||L||2||5|
|Panicum coloratum L.||Klein||BS||0.4-1.4||S||WDtCs||S||M||3||2|
|Panicum maximum Jacq.||Guinea||B||0.5-4.5||A,S||WDtCs||S||S||2||4|
|Pennisetum clandestinum Hochst. ex Chiov.||Kikuyu||SfSR||0.2-0.4||S||NDtCs||V L||4||5|
|Pennisetum purpureum Schumach.||Napier||B||2-6||S||WDtCt||V||M||1||2|
|Setaria anceps Stapf ex Massey||Setaria||B||1-2||S||WDtCs||SV||L||4||5|