Improved legume pastures increase economic value, resilience and sustainability of crop-livestock systems

Well-managed legume pastures play a crucial role in agricultural systems, contributing to strategies for the increasingly complex challenges of supplying meat and wool, improving soil fertility, increasing land use efficiency while minimising environmental impacts, and building system resilience. This paper examines the potential for a range of improved annual legume pasture species to deliver multiple benefits such as extending the length of the growing the season and closing feed gaps, boosting crop yields and farm profits, and contributing to natural resource management. Using MIDAS, a bioeconomic model of a crop-livestock farming system, we quantified the relative profitability and sustainability of five self-regenerating legume pasture scenarios − burr medic (Medicago polymorpha L.), bladder clover (Trifolium spumosum L.), French serradella (Ornithopus sativus L.), biserrula (Biserrula pelecinus L.) and common vetch (Vicia sativa L.) − against the baseline scenario of (mainly) subterranean clover (Trifolium subterraneum L.) for the medium-rainfall region of Western Australia. The modelling indicated that profit gains of more than 25% were possible by using an improved self-regenerating legume option when compared to a subterranean clover-based pasture system. This could be achieved through greater utilisation of land under pastures and higher stocking rates while still maintaining a major cropping program. The whole-farm economic benefits of improved legume pastures resulted from land use adjustments to sustain more profitable cropping and livestock enterprises, and benefits were small at low stocking rates. The combination of additional feed at the start of the season and slower loss of energy values at the end of the season in the improved pasture scenarios was an important profit driver for the livestock enterprise. Other benefits included projected savings in nitrogen fertiliser for crops in rotation with the pasture, greater sheep carrying capacity, improved efficiencies in supplementary feed and labour costs per animal, lower groundwater recharge, and improved farm business resilience overall. Pastures with higher nutritional value could lead to reduced net emissions per DSE if they allow ruminants to reach finishing weight faster or improve reproductive efficiency. This whole-farm study expands previous work by comparing a broad range of annual legume pasture species developed for the soils and climatic conditions of Western Australia. The general principles behind changes in land use revealed by the MIDAS modelling have wide application beyond this Australian region, confirming the potential role of well-managed legume pastures for achieving sustainable intensification of agricultural systems, while offering sufficient flexibility for grazing systems to cope with climate variability.