EVIDENCE FOR DIFFERENCES BETWEEN 3 WHEAT CULTIVARS IN YIELD RESPONSE TO PLANT-POPULATION

Three wheat cultivars were grown at five seed levels in 15 experiments under rain-fed conditions in the central wheatbelt of Western Australia in the 1986, 1987 and 1988 seasons. Guthea (released in 1982, 87 cm tall) required less seed and fewer plants on average to achieve its maximum grain yield than either Gamenya (released in 1960, 82 cm) or Aroona (released in 1981, 73 cm). At sites where Gutha was best adapted its optimum population was 65 plants m-2, about half of the population required by the other two cultivars. At sites where Aroona was best adapted its optimum population was 110 plants m-2. Gutha produced larger ears, especially at small populations, but did not increase kernel numbers per m2 in response to increased populations as much as Aroona. It is suggested that when a new cultivar is released its optimum plant population should be assessed in the area for which it is recommended.