Andrew.P.Smith, Bill Davoren, Rick Llewellyn, Damain Mowat, Vadakattu V.S.R. Gupta
CSIRO Agriculture, Waite Campus, PMB 2 Glen Osmond, South Australia, 5064
Peer review: Richard Hayes, DPI NSW
In regions with low annual rainfall (<350 mm annual rainfall), long summers, and poor-quality soil there are few green feed options for farmers for many months in the year when both feed quantity and quality are limiting. Consequently, supplementary feeding is often required to meet animal requirements. Forage shrubs can be particularly valuable during these times and extended periods of drought. Research to further develop the profitable use of forage shrubs, including new shrub options from the Enrich research program, was initiated under the Future Farm Industries CRC (which ran from 2007 to 2014).
In 2009 a field experiment including Old man saltbush (OMSB, Atriplex nummularia) and Mallee saltbush (Rhagodia preisii), one of the more promising alternative species, was established at Waikerie, South Australia with the aim to monitor shrub development, leaf biomass production and regrowth after grazing, and to investigate the effects of soil variability. In doing so the greater aim was to determine the potential contribution of perennial forage shrubs to modern mixed-farming systems in medium to low rainfall grain and livestock zones. The experiment ran until 2015. Here we summarise some key findings from 6 years of the field experiment.
• Forage shrubs are well adapted to climates with (low) variable rainfall – therefore the lower variation in feed supply between years mean that forage shrubs are a reliable source of feed,
• In most areas, and on most soils, farmers with OMSB can expect between 1-2 kg edible dry matter per shrub from plantations in most years,
• Soil type has a large influence on the amount of biomass produced by forage shrubs –rooting depth probably being one of the most important factors,
• The nutritional quality of shrubs seems less influenced by soil type,
• For OMSB, the root system contributed (on average across the different landscape positions) 67% of the total plant biomass,
• A model now exists that can be confidently used across soil types, regions and different grazing systems in the low and medium rainfall zone,
• The interrow is widely underrated and plays a critically important role in the livestock productivity of the forage shrub system