Effect of land preparation and nitrogen fertilizer on yield and quality of temperate species introduced into a tropical grass sward during autumn

Five temperate pasture species (Trifolium repens cv. Ladino, Trifolium subterraneum cv. Mt Barker, Lolium multiflorum cv. Tama, Lolium perenne cv. Kangaroo Valley, and (Lolium perenne x L. multiflorum cv. Ariki) were compared singly and in combination for their winter production when introduced into an existing couch and pangola mixed pasture grown under irrigation in tropical Queensland. The effects of preparing a cultivated seedbed and applying 50 kg N/ha.month on dry matter (DM) yield and in vitro dry matter digestibility (IVDMD) were studied. Nitrogen fertilizer increased the DM yields of all pasture types, (P < 0.05), but with a lesser effect on clovers and mixtures of clover and ryegrass than on ryegrass. Average DM yields for winter (April to September) were 5740, 3665 and 5238 kg/ha for nitrogen-fertilized clovers, ryegrasses, and clover and ryegrass mixtures, respectively. Corresponding DM yields without nitrogen were 4852, 874 and 4532 kg/ha, respectively. Clovers, and clover and ryegrass mixtures maintained a higher IVDMD than did the ryegrasses. Cultivation assisted early establishment of temperate pastures, though satisfactory pastures were also established after slashing and burning of the original couch and pangola mixed pasture. DM yields were higher for clover, and clover and ryegrass mixtures. Ryegrass did not persist without N fertilizer. It was concluded that clovers, ryegrasses, and clover and ryegrass mixtures could be introduced annually into existing couch and pangola mixed pastures to provide winter forage in a tropical environment.