A ley-farming system for marginal lands based upon a self-regenerating perennial pasture legume

Abstract

Annual-based farming systems represent some of the most highly disturbed terrestrial ecosystems on the planet. They are also highly exposed to climate variability. Many wheatbelt systems of southern Australia rotate annual crops with annual pastures, where the productivity of both is reliant upon seasonal rainfall. Perennial plants, in contrast, are less reliant upon both consistent rainfall and annual establishment, so one approach to decrease exposure to climate variability and disturbance in agriculture is to increase the proportion of the farm sown to perennial species. Perennial pasture or forage species offer immediate possibilities for transformation of agricultural ecosystems as they offer high protein feed to animals, often when green feed is most limiting, and concomitantly restore soil fertility. However, there are no perennial forage legumes adapted to acid and infertile soils in low-rainfall regions of the developed world, either in temperate or Mediterranean climates. Here, we review the recent research efforts to domesticate a perennial legume for these regions. Reasons for the lack of success are provided by a comparison of the attributes of the legumes evaluated in recent research programs and the limitations of these legumes as assessed by reviews and publications. This manuscript outlines an alternative approach to domestication of perennial forage legumes for acid soils and introduces new concepts in ley farming in an Australian context that might support the development of more sustainable agro-ecosystems. It highlights situations where very hard-seeded annual legumes have been successfully included in modern intensive cropping systems, and where perennial legumes may underpin ley-farming systems on infertile soils that normally produce low crop yields. Both innovations require the legume and their nodule bacteria to be sown only once in decades and address concerns about the sustainability of modern agro-ecosystems.