Establishment and productivity of three perennial grass species overdrilled into lucerne

Abstract The effects of irrigation and fungicide seed treatment on the establishment and growth of perennial grasses overdrilled into lucerne (Medicago sativa L.) were investigated. Phalaris aquatica cv. Grasslands Maru, Bromus willdenowii cv. Grasslands Matua, and Lolium perenne cv. Grasslands Nui were overdrilled into 5‐year‐old lucerne in spring in a dry, subhygrous environment. At 250 days after sowing (DAS), the seedling population was only 11 % of the peak value, with significant differences in survival between species of 29, 45, and 60 plants/m 2 for Nui, Maru, and Matua respectively. Irrigation did not significantly affect seedling establishment or survival and had no effect on seedling growth where the lucerne canopy was closed, but increased seedling weight by 77% where the canopy was open. Similarly, seedling growth at 40 DAS was no different for all species under the closed canopy but Matua seedlings were 35% heavier than Nui where this was open. Matua seedlings had a leaf area which was 2–4 times that of the other species and a root mass which was 25–30% larger than the other grass species at all times except shortly after sowing. During the establishment year, total yield from rainfed overdrilled grasses was low (0.45 t DM/ ha). Irrigation increased this to 2.821 DM/ha. Under rainfed conditions, Matua produced 0.97 t DM/ha, 5 times that of the other species. Irrigated Matua produced 4.961 DM/ha, nearly double the yield of the other species. There was no difference in total sward yield between pure lucerne and any of the overdrilled treatments. Overdrilled swards had 40–80% less weed growth than pure lucerne in the winter and early spring. Fungicide seed treatment had no effect on the establishment and productivity of the grasses. It is concluded that the overdrilling of lucerne with grasses in a dry subhygrous environment can be achieved successfully by using upright grasses able to establish a large leaf area quickly. However, significant production from these will only be obtained if the lucerne canopy is relatively open, and the stand is irrigated.