Seasonal growth patterns and response to nitrogen of some perennial grass varieties in two environments.

The seasonal productivity of eight perennial grass varieties at three nitrogen levels was measured in small pure grass swards at Badgery's Creek, N}S.W., and at "Coolamatong", Orange, N.S.W. Although climatic conditions differ at these two locations, a period of low pasture production from May to September is common to both. The experiment began on previously established plots in early autumn, 1964, and finished in late winter, 1965. The ungrazed swards were cut at l%-monthly intervals. Nitrogen treatments were reapplied immediately after cutting. The plots were irrigated at Badgery’s Creek, but not at "Coolamatong". Many plants failed to survive the dry summer and autumn, 1965, at "Coolamatong". Plant survival was adversely affected by high rates of nitrogen application. Phalaris tuberosa was the most persistent variety, followed by Currie cocksfoot, Brignoles cocksfoot, Demeter fescue, Oregon fescue, Danish cocksfoot, Kangaroo Valley ryegrass, and Victorian ryegrass. In summer and early autumn at Badgery's Creek, with irrigation, tall fescue and cocksfoot varieties significantly outyielded phalaris and ryegrass. It is expected that tall fescue and cocksfoot varieties are capable of useful summer growth at Orange in years of normal summer rainfall. At both locations, Kangaroo Valley ryegrass and Currie cocksfoot were the highest yielding varieties in the period of greatest feed shortage (May to September), yielding up to 40% greater than phalaris, and up to 200% greater than Danish cocksfoot. With adequate nitrogen, the dry matter produced by Kangaroo Valley ryegrass and Currie cocksfoot in the autumn to early spring period was nearly as great as that produced over a similar period by oats in earlier experiments at Badgery's Creek and "Coolamatong". Under the conditions of the experiment, the response to applied nitrogen (up to 500 lb N/acre/annum) was linear in all seasons at Badgery's Creek. At "Coolamatong" in spring, late autumn, and winter, nitrogen applied at the rate of 300 lb N/acre/annum (medium level) significantly increased the productivity of all grass varieties compared with that at the low level of nitrogen (100 lb N/acre/annum). The lack of a significant difference in annual dry matter production between the medium and high nitrogen treatments was primarily due to the depressing effect of nitrogen on plant survival. At both sites, grass gave a greater response to nitrogen in late winter than in late autumn or early winter. This is discussed in relation to plant growth and climatic factors. Kangaroo Valley ryegrass used nitrogen more efficiently than the other grasses in late autumn and late winter, at both sites. The difficulty of extrapolating the results of this experiment to grass—clover swards in the County of Cumberland and Central Tablelands regions is discussed. Soil temperature records are used to predict favourable times for the application of nitrogen to grass—clover pastures at Badgery's Greek and Orange, but further experiments are considered necessary to assess the profitability of using artificial nitrogen on pastures and fodder crops in these environments. KangarOO Valley ryegrass, Currie cocksfoot, and Phalaris tuberosa are the varieties suggested as companion grasses for clover in future experiments