Opportunities for plant improvement to increase the value of forage shrubs on low-rainfall mixed farms

Abstract

Plantings of forage shrubs such as saltbush (Atriplex spp.) in the drier part of the crop–livestock zone of southern Australia have the potential to help fill feed autumn gaps, provide valuable feed during drought periods, and provide year-round groundcover, shelter for livestock and options for management of saline soils. However, the proportion of farms with forage shrub plantings and the extent of those plantings remain relatively low, with the rate of new plantings slowing over the past decade. Development of new forage-shrub options has been occurring with the aim of improving the feed value and adoption of forage shrubs. Using a whole-farm bio-economic optimisation model for a crop–livestock farming system in the low-rainfall Mallee region of southern Australia (Mallee MIDAS—model of an integrated dryland agricultural system), we explored how key attributes of forage-shrub plantings and the associated pasture understorey, such as biomass growth, digestibility and ease of establishment, can make forage shrub plantings economically more attractive to farmers. We found that saltbush types and forage-shrub options with improved feed quality characteristics will offer the opportunity for improved economic returns and increased profitability from larger plantings compared with existing options. Improving feed quality was more important than increasing the growth rates of saltbush plants. Results still indicate only a niche role in farming systems, with profit typically being greatest when using relatively small areas (<10% of farm area) on the less productive soils of the farm. The results suggest that the profitability of forage shrubs will be greatest for those growers with larger areas of marginal cropping soils and greater reliance on livestock than cropping. Furthermore, the results demonstrate that, if cereal prices or yields fall significantly and/or lamb prices rise, the value of a forage shrub planting can increase substantially. The principles revealed have wide application beyond the region, although these need to be adapted on-farm and widely disseminated before potential contribution to Australian agriculture can be realised.