Pasture Production of Annual, Hybrid and Perennial Ryegrasses in Cool and Warm Temperature Climates

Pasture production and persistence of 8 ryegrass species-cultivars were evaluated under 2 grazing frequencies (infrequent and frequent) in a cool temperate climate (Southland) and a warm temperate climate (Manawatu) in New Zealand. All pastures were sown with white clover (Trifolirim repe11s) and rotationally grazed with sheep for 3 years. The 8 ryegrass lines were divided botanically into cultivars of annual ryegrass (Lo/ium muftljlorum), hybrid ryegrass (L. boucl1eanu111) (most of the parentage derived from L. multiflorum) and perennial ryegrass (L. pere,me). Infrequent grazing resulted in higher yields and particularly higher ryegrass yields, but lower ryegrass tiller numbers at the cool site. At the wann site, annual ryegrass suffered greatly from frequent grazing both in terms of yield and tiller numbers over the summer, and hybrid ryegrass to a lesser extent. Hybrid and perennial ryegrasses at the cool temperate site had high production for 3 years. It is concluded that the production and persistence of annual and hybrid ryegrasses at the cool site was enhanced by the cool, moist summers, encouraging tillering and reducing dainage by the pasture pest Argentine stem weevil, In contrast, the warm, dry summers at the warm site reduced tillering and increased damage by Argentine stem weevil. The relative importance of these factors, and the influence of natural reseeding, are not known.