Legume yield and persistence in grass and herb pasture mixtures in Lees Valley, South Island High Country

Abstract

Four experiments were established to identify productive and persistent dryland pasture mixtures that included legumes to supply nitrogen and a suitable grass and/or herb companion species. There was a Caucasian clover-herbs (plantain and/or chicory) mixture experiment, and three grass-clover mixture experiments: ryegrass cultivars, dryland grass species (brome, cocksfoot, or tall fescue), or timothy +/-herbs (plantain and/or chicory), all sown with white and sub clovers. The site was in Lees Valley, an intermontane basin in North Canterbury (400 m a.s.l.), which experiences long cold winters, has soils of low pH and high aluminium, with low water holding capacity and severe summer soil moisture deficits. In the first two years of the grass-clover mixtures, the ryegrass and dryland grass-clover pasture mixtures were the most productive with total yields of ~4,400 kg DM/ha. In the dryland grass mixtures, the yield of the brome and cocksfoot grass component increased from Year 1 to 2 (1350 to 2830 kg DM/ha) while tall fescue declined (970 to 800 kg DM/ha). The equivalent timothy grass yields were low averaging ~320 kg DM/ ha/yr. Across the grass-clover mixtures, the average white clover yield was 1800±210 kg DM/ha in Year 1 and represented 43% of total DM, compared with 8% sub clover. In Year 2, the white clover produced 930±90 kg DM/ha, which represented 29% of total annual yield. Sub clover did not re-establish. Grass cultivars/species in the mixture experiments had no effect on white clover yield. White clover yields peaked in October-November of both years with growth rates of ~16 kg DM/ha/d. At the start of the summer dry period, from November onwards, white clover growth rates declined resulting in lower yields. In the Caucasian-herbs experiment, total yield in Years 1 and 2 was ~2750 kg DM/ha/yr. In both years Caucasian clover yields were lower when grown in herb-based mixtures compared with a monoculture (Year 1: ~400 versus 1800±270 kg DM/ha, Year 2: 920 versus 1750±210 kg DM/ha). Plantain contributed ~1740 kg DM/ha/yr to the total yield. The persistence and productivity of grass-legume-herb mixtures for dryland pastures are discussed. Cocksfoot was a productive grass in Lees Valley because of its aggressive growth habit and resilience in dryland conditions. Caucasian clover was a productive when grown as a monoculture.