DIFFERENTIAL RESPONSE OF TIMOTHY CLONAL LINES AND CULTIVARS TO SOIL TEMPERATURE, MOISTURE AND FERTILITY

Six clonal stocks of timothy (Phleum pratense L.) were tested under different soil environmental conditions in the greenhouse using three soil temperatures, two moistures and four nutritional levels. The average herbage yields from the various environmental conditions showed that the four parental selections of ’Champ’ were in the order of S-5 = S-9 > S-2 = S-6. Under high nutrition (N 1 P 1 ) and soil moisture (75% available water) S-5, S-9, and Drummond yielded the largest at a soil temperature of 10 C, S-5 and S-9 yielded the most at 20 C, and S-2 the highest under a soil temperature of 27 C (day) and 20 C (night). Under low nutrition the differences among the selections were small. Under high nutrition, a change in temperature from 10 to 20 C increased late seasonal growth but had little effect on early growth, with an overall Q 10  = 0.23, while under low nutrition, a similar change in temperature increased both early and later growth with a mean Q 10  = 1.83. There was a delay in the optimum rate of regrowth with increase in temperature (10, 20, to 27/20 C). The S-5 tillered well at the lower temperatures, S-6 at the higher temperatures, and S-9, at all three temperatures.The yield potential of Champ appears to be similar to the two cultivars under low soil temperature and nutritional condition but greater than them under higher soil temperatures, nutrition and moisture.