The South African perennial legume Lebeckia ambigua sustainably supports livestock production on infertile soils in rain-fed agro-ecosystems

Abstract

Lebeckia ambigua is a perennial legume endemic to rangeland South Africa that is adapted to dry (< 400-mm annual rainfall), infertile and acidic (below pH 5.5 Ca ) soils. Although it is considered that the legume was grazed by mammalian ungulates during its evolution, little is known about its production, nutritive value for grazing animals or optimal management in an agricultural context, in either its centre of the origin or in Australia. Experiments were conducted to test the hypotheses that sheep would graze L. ambigua in autumn without adverse effects on either the animal or the plant. Lebeckia ambigua was established at two sites in Western Australia. In experiment 1, three grazing intensities were imposed by exclusion cages introduced during a single intensive grazing period, to provide differing residual pasture heights. The metabolisable energy and crude protein content of L. ambigua were more than 11.4 MJ/kg dry matter and 21%, respectively for all treatments. Un-grazed L. ambigua produced 1740 kg DM/ha while a single moderate or severe grazing reduced total biomass production by about 50% over 10 weeks post-grazing (P < 0.001). In experiment 2, continuous grazing of L. ambigua for 64 days had no negative impacts on biochemical health indicators of merino wethers. Grazing had no effect on plant density in either experiment indicating that L. ambigua is adapted to substantial grazing pressure in autumn. Lebeckia ambigua could become a valuable plant for sustainably increasing livestock production on infertile soils in rain-fed agro-ecosystems where other legumes fail.

Defoliation enhances the positive effects of soil microbial diversity on plant productivity

“…It is worth noting that defoliation had no significant effect on the legume ANPP but significantly decreased grass and forb ANPP (Figure 2), contributing to the reduction of community ANPP. Legume is tolerant to defoliation and has stronger regeneration than grass, which may play a key role in maintaining plant community composition and productivity under defoliation (Howieson et al, 2021).…”