Melilotus albus (Medik.) is productive and regenerates well on saline soils of neutral to alkaline reaction in the high rainfall zone of south-western Victoria

Abstract

Dryland salinity is a serious problem in Australia. While some introduced perennial grasses such as tall wheat grass (TWG) Thinopyrum ponticum (Podp. Z.W. Liu & R.R.C. Wang) are adapted to saline soils, there are few pasture legumes that are productive and persistent under saline conditions. Melilotus albus (Medik.) has the potential to be 1 such legume in southern Australia. To test the potential of this species, we conducted 2 experiments over a 3-year period on saline soils at Woorndoo and Glenthompson in south-western Victoria. The soil electrical conductivities (1 : 5 water) of the sites, in autumn before sowing, were 1–3 dS/m at Woorndoo and 3–5 dS/m at Glenthompson (0–10 cm depth).At both sites the herbage yields of 2 Melilotus lines were greater than 10 t/ha of dry matter for the whole season between autumn and late summer. The best commercial control species at Woorndoo, white clover cv. Haifa, produced less than 1/6 of the yield of the best Melilotus line during the summer months. At Glenthompson, during the whole second season the herbage yield of the best Melilotus was 40% greater than that of the best commercial control, Persian clover cv. Nitro plus. In the second season, regeneration of Melilotus at both sites was excellent, averaging 3500 seedlings/m2 at Woorndoo, and 1100 and 3400 seedlings/m2 in mixtures with TWG and in monoculture, respectively at Glenthompson. In the third season, however, regeneration averaged only 400 plants/m2 at Woorndoo and 640 plants/m2 at Glenthompson, both with and without grass. It appears that, when there is limited competition, Melilotus albus dominates in the first 2 years. However, as fertility and water use increase, other pasture species, which initially have a low rate of survival and are unproductive, begin to increase their presence in the sward at the expense of M. albus. These annual species germinate after the autumn rains dilute the salt on the surface of the soil and senesce in early summer as soil water deficits and/or evaporation increase the electrical conductivity again. We suggest that Melilotus albus is an excellent pasture legume to revegetate saline soils in southern Australia and represents an opportunity to obtain high levels of out-of-season pasture production from areas that are currently unproductive.