Effects of shade on the growth of Poa trivialis and perennial ryegrass

Abstract

P. trivialis and perennial ryegrass sown in autumn for common emergence date were shaded from the 25th to 81st days after emergence to 40, 25, 15, or 5% of full daylight. At the 25th day, total plant dry weight (leaf, stem, and root), leaf area, and numbers of tillers were greater for ryegrass than for P. trivialis. Relative growth rate of P. trivialis from the 25th to 81st days exceeded that of ryegrass. The pattern of species response to the shade treatments was similar for both species. Specific leaf areas were higher for P. trivialis than for ryegrass, but ratios of leaf weight to total weight were similar for both species.

Relative growth rate of an erect growth form of P. trivialis was greater than that of a prostrate growth form in full daylight and 45% light, but not under 10% light.

Competitive ability of the prostrate form of P. trivialis in 50:50 association with ryegrass in simulated swards cut from 17.8 cm to a stubble of 2.5 cm was less than that of the erect form, probably because of lower tillering ability.