Phalaris (Phalaris aquatica cv. Sirosa)-based pastures at Sandy Creek (north-eastern Victoria) and Flaxley (South Australia) were subjected to grazing strategies based on different pre- and post-grazing pasture dry matter levels for 3 years, 1994–96. At Sandy Creek, 3 treatments consisted of commencing grazing when either 1600 (1), 2200 (2) or 2800 (3) kg dry matter per hectare (DM/ha) of pasture had accumulated, with treatments being grazed to a pasture residual of 1200 kg DM/ha. Grazing strategies were imposed over autumn–winter. At Flaxley, there were 5 treatments. Grazing commenced when either 1800 (1) or 2200 (2) kg DM/ha of pasture had accumulated, and was grazed to a pasture residual of 1200 kg DM/ha. Also when either 2200 (3) or 2600 (4) kg DM/ha of pasture had accumulated and these treatments were grazed to a pasture residual of 1800 kg DM/ha. A further treatment was when phalaris had reached a 4-leaf stage (5) (4 fully expanded leaves per tiller) and this was grazed to a residual of 1200 kg DM/ha. The grazing strategies were imposed over the autumn, winter and spring. Pasture consumption at Sandy Creek was higher in treatments 2 and 3. Pasture metabolisable energy (ME) levels and crude protein contents were not affected by treatment. Pasture consumption at Flaxley was greater in treatments 2 and 4. The strategy of grazing at the phalaris 4-leaf stage (5) showed potential for large spring growth. The ME of pasture was unaffected by treatments. The optimal grazing strategy to increase pasture growth for phalaris cv. Sirosa-based pastures in winter-dominant rainfall zones of temperate Australia, receiving about 700 mm average annual rainfall appears to be: allowing 2200 or 2600 kg DM/ha of pasture to accumulate before grazing back to a pasture residual of 1200 or 1800 kg DM/ha, respectively.

Barley grass (Hordeum spp.) in a subterranean clover pasture was controlled with herbicides in the time between the 2-3 leaf stage and flowering. The effects on subsequent pasture production and composition were measured and the interaction between grazing and herbicides was also assessed. Early removal of barley grass reduced dry matter production in winter by an average of 41%. It also allowed an incursion of Indian hedge mustard (Sisymbrium orientale L.). which was suppressed by grazing but comprised an average of 23% ground cover in ungrazed pasture. Loss of total pasture production decreased as the date of herbicide application was delayed from June to September. Broadleaf species compensated for the early removal of barley grass, so that total dry matter production in spring in herbicide-treated areas was higher than in the unsprayed pasture. Fluazifop-p at 32, 53, and 106 g a.i/ha gave, respectively, 94, 91, and 94% reduction in barley grass seedhead density when applied at the 2-3 leaf stage, and 64, 88, and 98% reduction when applied at mid jointing. Application of this herbicide at 53 or 106 g a.i/ha for barley grass control can be delayed until late winter, thereby maintaining winter feed production but avoiding declining palatability and awned barley grass seeds.

No abstract

Water-dropwort (Oenanthe pimpinelloides L.), a tuberous perennial herb, is currently known in South Australia from only a single locality in the Mount Lofty Ranges. There is little information on water-dropwort control, and 2 experiments were conducted to assess the effects of sowing pasture, with or without presowing herbicides, on the control of this weed. Phalaris (Phalaris aquatica L.) and perennial clovers were successfully introduced into infested pastures by direct drilling in autumn. Water-dropwort regenerated from seed more densely in unsown plots than plots of established perennial pasture, suggesting that upgrading pastures may be a strategy to reduce the rate of spread by seed of this weed. A range of herbicide treatments applied to waterdropwort at the stem elongation stage in spring before autumn sowing of pastures provided effective shortterm control. The best short-term control was provided by glyphosate at 1440 g a.i./ha; metsulfuron methyl at 6, 12, and 36 g a.i./ha; and metsulfuron methyl at 12 g a.i./ha tank-mixed with glyphosate or 2,4-D amine at 720 or 1000 g a.i./ha, respectively. These treatments, and chlorsulfuron at 21 g a.i./ha, also significantly (P<0.05) reduced water-dropwort abundance (relative to untreated areas) for up to 18 months after sowing and initially improved the density of sown pasture species, but these improvements were not evident 14 months after resowing. Although prior season herbicide treatments controlled water-dropwort in newly sown pastures, 2 separate applications of herbicides, in May and October, gave no better control of water-dropwort than a single herbicide application in spring. Water-dropwort infestations do not appear to prevent successful direct drilling of phalaris and perennial clovers. Although pasture renovation did not provide long-term suppression of water-dropwort, the maintenance of vigorous pastures may reduce the rate of population growth from seedlings of this weed. Recropping restrictions may limit the role of chlorsulfuron for water-dropwort control in pasture renovation situations.