Grazing System and Grazing Pressure Effects on Herbage and Lamb Production from Subclover Interseeded Annual Grassland

Information on management effects on the productivity of improved mediterranean annual grassland pastures in California is limited, Our objectives were to compare herbage and lamb production in subclover (Trlfolium subterraneum L.)-seeded annual grassland under different intensities of continuous and rotational systems of grazing. Grazing systems at 3 grazing pressures were applied in a factorial arrangement to 12 0.6S-ha pastures in a randomised complete block design replicated twice. Targhee lambs grazed pastures from 28 February to 9 May in 1989 and from S March to 1 May in 1990. Lambs occupied each of the eight paddocks in rotations for 1-4 days, depending on herbage growth rates. Lamb numbers were adjusted monthly to provide herbage allowances of approximately 41, SS and 70 kg DM/lamb at high, medium and low grazing pressures. Season-long average dally gain was higher under continuous grazing (0.17 v. 0.10 kg) but unaffected by grazing pressure (range 0.14-0.18 kg) in 1989, and in 1990 was higher under continuous grazing (0.24 v, 0.17 kg) but unaffected by grazing pressure (avg, 0.20 kg), Season-long gain/ha was higher under continuous grazing in both years (1989: 194 v. 154 kg; 1990: 221 v. 18S kg), was unaffected by grazing pressure in 1989 (range 163-194 kg) and increased with grazing pressure in 1990 (179 to 223 kg),