Ecology of herbaceous perennial legumes: a review of characteristics that may provide management options for the control of salinity and waterlogging in dryland cropping systems

Abstract

Salinity is a widespread problem caused by an imbalance between rainfall and transpiration in the dryland cropping systems of southern Australia. The need to use more perennials has been identified and this paper examines the possibility of replacing annual with perennial pasture legumes and the germplasm available to do so. While lucerne is already used widely in eastern Australia it has only recently been adopted in the wheat belt of Western Australia. There are doubts about its adaptation to acid soils and to climates where summer rainfall is low and ambient temperatures are high. There is also a need to diversify the species available to reduce the likelihood of invasion by exotic diseases and insects. Several genera are likely to be of value in this respect, although few will be as widely adapted as lucerne. Perennial legumes are found in environments ranging from alpine to desert. Targeted collections of genera from the dry areas, especially where soils are acid, are likely to yield species of value. These may include perennial species of Astragalus, Hedysarum, Lotus, Onobrychis, Psoralea, and Trifolium. Some Australian genera, for example Swainsona, Glycine, and Cullen may also be of value. Most of these genera are from alkaline soils, and the need to cope with acid soils that are often high in free aluminium is seen to limit their use in southern Australia. However, since virtually nothing is known of the ecology and ecophysiology of species from the dry areas, it is possible that through selection and the use of adapted rhizobia, some at least may be of value in Australian conditions. Cropping in rotation with perennial legumes is likely to involve several changes in farming systems. It is impossible to predict their nature but it is essential that we understand what these changes are before the species are widely introduced. Account must also be taken of their ability to use water. It is entirely possible that perennials from dry areas are dormant in summer despite the fact that there is no evidence in the literature to this effect. It was concluded that although lucerne is suitable for phase farming, alternatives to lucerne are needed. They will have to match the water-using and nitrogen-fixing capacities of lucerne, and farming systems will be required that make full use of the new germplasm. Collaboration with institutions in the Mediterranean basin and elsewhere is needed and a beginning has been made in this direction.

Genetic variability and inheritance of aluminium tolerance as indicated by long root regrowth in lucerne (Medicago sativa L.)

“…This is also true for lucerne or alfalfa (Medicago sativa L.), a widely cultivated, deep-rooted, perennial pasture legume. The use of lucerne as a valuable fodder plant is considerably limited by its lack of tolerance to soil acidity (Bouton 1996;Campbell et al 1994;Cocks 2001;Eticha et al 2005;Parrrot and Bouton 1990). Breeding for acid-tolerant and/or Al-tolerant cultivars appears to be the most economically viable solution to the acid soil problem, because genetic selection for acid soil tolerance offers an avenue for increasing plant production and reducing production cost (Samac and Tesfaye 2003).…”

Prioritisation of novel pasture species for use in water-limited agriculture: a case study of Cullen in the Western Australian wheatbelt

“…Climate change and the growing global population's demand for water and land are increasing pressure on agriculture to produce food using less water or from areas receiving less rainfall (Neumann 2008; Rosegrant et al 2009). Existing perennial pasture species, however, show poor growth and survival in low-rainfall areas or drought conditions (Cocks 2001;Dear et al 2003). The search for novel perennial pasture species to address this shortage is impeded by the lack of knowledge about putative pasture species that are, as yet, undomesticated and by the often limited germplasm collections of novel species that are available for evaluation.…”

Use of functional traits to identify Australian forage grasses, legumes and shrubs for domestication and use in pastoral areas under a changing climate

“…Most are perennials with occasional biennials and very few annual species, and their growth habits range from prostrate, twining to upright (Cocks 2001). Many of them have their major growth period in the warm season, even in southern parts of the continent, whereas others behave as yearlong green species (Lunt et al 1998;Cocks 2001). All legumes are C 3 species.…”

“…However, with the introduction of sown pastures and cropping, they have largely disappeared from the higher rainfall parts of the country, except for areas that have been retained as predominantly native pastures or in reserved areas. Most are perennials with occasional biennials and very few annual species, and their growth habits range from prostrate, twining to upright (Cocks 2001). Many of them have their major growth period in the warm season, even in southern parts of the continent, whereas others behave as yearlong green species (Lunt et al 1998;Cocks 2001).…”

“…Many species of native legumes contain toxic elements that render them unsuitable for grazing (Cocks 2001), and those best known among the grazing industry are species of Swainsona commonly called the Darling peas. There are~85 species in Australia (McKenzie 2012) and they occur right across the country, but the records are sparser in the driest parts and in the tropical north (AVH 2014).…”