Medicago sativa and Desmanthus virgatus: suitable perennial legumes in mixes with Digitaria eriantha in Australia during drought

Abstract

Tropical perennial grasses are an important forage option in the frost prone, summer dominant rainfall zone in eastern Australia. These pastures commonly lack a companion legume and are, at best, irregularly fertilised with nitrogen; therefore, their production potential is not realised. We conducted a study during 2012–16 to evaluate the productivity and persistence of a range of cultivars/lines of eight tropical and two temperate perennial legumes in mixes with digit grass (Digitaria eriantha cv. Premier) at two sites (Bingara and Manilla) in the northern inland region (North-West Slopes) of New South Wales. The sites were subjected to dry conditions during the assessment period, with the Bingara site receiving <25th percentile rainfall for 2 years of the study. Lucerne (Medicago sativa) was the most productive companion legume, with mixes producing 16–18 and 38–46 t dry matter (DM)/ha at the Bingara and Manilla sites respectively. Cultivars of Desmanthus spp. were less productive, with the best performing in mixes producing 13 and 21–23 t DM/ha at Bingara and Manilla respectively. These cultivars were also persistent and readily recruited new seedlings. Their persistence was similar or superior to lucerne, which appeared to be declining, especially at the Manilla site. Mixes of burgundy bean (Macroptilium bracteatum) and digit grass produced 14–17 t DM/ha at the sites but DM tended to decline during the course of the experiment, especially at the Manilla site. Stylosanthes spp. and Chamaecrista rotundifolia had poor persistence, generally failing within 1–2 years of sowing. Therefore, we recommend lucerne and Desmanthus virgatus cvv. Marc and JCU 2 as suitable perennial legumes in mixes with digit grass during drought conditions.