Grazing management to increase utilisation of phalaris-based pasture in dryland dairy systems

Abstract

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.