Studies of Tiller Formation in Reed Canarygrass (Phalaris arundinacea L.) and ‘Climax’ Timothy (Phleum pratense L.)1

The greenhouse and growth chamber experiments reported herein were set up to investigate the influence of the following factors on tillering of ‘Climax’ timothy, Phleum pratense L., and reed canarygrass Phalaris arundinacea L., (a) stage of development at which the first harvest was removed; (b) clipping height; (e) nitrogen level; (d) day‐night temperature; and (e) shading. Stages of development at the time the first harvest was removed were as follows: for Stages 1, 2 and 3 the growing points were 5, 10 and 20 cm, respectively, above the soil surface; Stage 4 was 2 weeks after Stage 3. Tillering was affected as follows by these treatments: Climax timothy plants from Stages 1, 3, and 4 showed no increase in thc number of tillers formed between the 1st and 2nd harvests, but increased thereafter. Tillering under Stage 2 increased between the 1st and 2nd harvests, and declined between the 2nd and 3rd. Plants clipped leaving 10‐ vs 4‐cm stubble showed a 30% increase in the number of tillers formed. Tillering was increased significantly (18%) by the high rate of N (112 vs 28 kg/ha). Reed canarygrass plants clipped at Stages 1 and 2 demonstrated an increase in tillers of 2.6 times between the 1st and 3rd harvests. Those clipped at Stage 3 and 4 performed similarly to the above stages between the 1st and 2nd harvests, but showed no increase thereafter. Plants clipped leaving 10‐ vs 4‐cm stubble produced 26% more tillers. No N treatments were applied to reed canarygrass. The number of tillers formed under high day‐night (32–27C) temperatures was less than the number under the 21–15.5C regime for both species. Climax timothy was more susceptible to injury when subjected to the higher temperature. Both species produced more tiller when shaded (40% of full light intensity received) regardless of whether the day‐night temperature was 32–27C or 21–15.5C Dry matter production of reed eanarygrass was approximately equal regardless of whether the first harvest was removed at Stage I or Stage 4, or whether the clipping height was 4‐ or 10‐cm. Climax timothy produced less dry matter when the first harvest was removed at the two earlier stages of maturity, but no difference was found between the 4‐ and 10‐cm clipping heights.