Annual pasture legumes for farming systems in cool-temperate areas with summer soil moisture deficits

Abstract

Seed softening rates of subterranean clover (Trifolium subterraneum) are lower in cool-temperate environments than in typical Mediterranean areas, allowing the accumulation of large seed banks. These large seed banks should enable a pasture to selfregenerate following a year of cropping in which the pasture has been removed. To test this hypothesis, a 1:1 pasture/crop rotation system was established at three sites in southern Victoria, Australia, with subterranean, balansa (T. michelianum), Persian (T. resupinatum) and arrowleaf (T. vesiculosum) clovers. At Hamilton, pure subterranean clover herbage yields of up to 10 t DM/ha were obtained under grazing. This was followed by wheat grain yields averaging 7 t/ha with 12.7% grain protein over three seasons. After a year of dryland cropping, the pastures selfregenerated with more than 3 000 clover seedlings/ m2. At Gnarwarre and Streatham, all four clover species were well adapted to the pasture/crop rotation in terms of their seed-seedling dynamics, with the highest regeneration after cropping at 8 000 seedlings/m2 in balansa clover and the highest seasonal herbage production of 12.8 t DM/ha in arrowleaf clover. No nitrogen fertiliser was applied in the system. Key words: annual legumes, cool-temperate climate, crops, seed softening rates