The effect of shade and shade material on white clover/perennial ryegrass mixtures for temperate agroforestry systems

White clover/perennial ryegrass mixtures (Trifolium repens L., Lolium perenne L.) are potential understory candidates for temperate agroforestry systems. A 2-year artificial shade experiment was conducted to determine the effects of shade on herbage production and quality and on changes in sward composition under field conditions. Wooden frames covered by shade cloth or a slatted structure were used on the sward to mimic different shade patterns of trees. The sward was exposed to 30, 50, and 80 % reduction in sun irradiance as well as a non-shaded control (0 % reduction). Total annual herbage production was highest in non-shaded swards in second and third year after establishment (8 and 16 t DM ha(-1), respectively) and declined with increased shade (up to 70 % with 80 % shade). Compared to the control (24 t ha(-1)), 50 % shade cloth and 50 % slatted structure reduced biennial herbage production by 4 and 7 t ha(-1), respectively. A decline in clover content of up to 93 % under severe shade compared to the control in the second year of the field experiment highlighted the sensitivity of clover to reduced radiation. No differences in forage nutritive qualities were detected in response to shade intensity during either growing season. On a dry matter basis, average biennial quality values were 2.7 % N, 41.8 % NDF, 34.4 % ADF, and 4.7 % ADL. The findings of the biennial field experiment confirm a white clover/perennial ryegrass sward is a suitable understory under light to moderate shade conditions; however, within a temperate agroforestry practice under dense shade, sward productivity and clover content will rapidly decline. Long-term effects of shade on white clover/perennial ryegrass mixtures as an understory in temperate agroforestry systems need to be evaluated in future research activities.