Pelformance of perennial ryegrass and cocksfoot cultivars under tree shade

The shade from trees in silvopastoral systems potentially decreases the persistence and production of pasture species by reducing tillering and shoot dry weight accumulation. However data from a glasshouse trial indicated that cocksfoot (Dactylis glomerata L.) had better tolerance to shade than other pasture species at the lowest photosynthetically active radiation. To verify the results obtained in the glasshouse, and also to evaluate whether any differences exist among cocksfoot cultivars in terms of shade tolerance attributes, seven cultivars of cocksfoot along with perennial ryegrass (Lolium perenne L.) cv. Grasslands Nui were field tested under 11-year old alder trees at the Horticultural Research Centre, Aokautere. A split-plot design with four replicate blocks was employed for the experiment. The main plot treatments were three levels of photosynthetic photon flux density (PPFD) (77%, 27%, and 17% of full sunlight) created by pruning trees to different heights. The sub-plot treatments were pasture species and cultivars grown at first in a glasshouse and then transferred in pots to the field. Five plants per pot were maintained and plants were watered daily. Water and fertilizer were non-limiting. The experiment ran from 3 February to 30 April, 1997. Tillers per plant and shoot dry weight were assessed 5 times at 15 day intervals and leaf area, leaf dry weight, specific leaf area, and root dry weight per plant were determined at the final harvest. Shade affected ryegrass more than all the cocksfoot cultivars, especially at the low PPFD. Eighteen tillers were produced in ryegrass compared with twenty nine (p<0.001) for cocksfoot cv. Grasslands Wana at the final harvest. Ryegrass leaf area per plant was also significantly (p<0.001) lower (1559 mm2) than cocksfoot cv. Grasslands Wana (8163 mm2), and similarly for relative specific leaf area, and leaf dry weight at the low PPFD. Cocksfoot cultivars were better able to tolerate low PPFD than perennial ryegrass, and cv. Grasslands Wana was a particularly shade tolerant