Productivity and water use of seven pasture grasses when sown alone and in binary mixtures

Abstract

Three experiments were conducted on a Wakanui silt loam between 6 March 1991 and 26 February 1993. These examined the grass treatments for: production (28 grass treatments, seven single sown and 21 binary mixtures), water use (12 treatments), and maximum water extraction depths (three treatments). The seven grass species used were: 'Grasslands Gala" grazing brome (Bromus stamineus), 'Grasslands Hakari' upland brome (Bromus sitchensis L.), 'Grasslands Roa' tall fescue (Festuca arundinacea Schreb.), 'Grasslands Marsden' hybrid perennial ryegrass (Lolium x boucheanum), 'Grasslands Maru' phalaris (Phalaris aquatica), 'Grasslands Wana' cocksfoot (Dactylis glomerata), and 'Grasslands Kahu' timothy (Phleum pratensis). The 21 binary mixtures were all possible binary combinations of these seven species.

The first experiment investigated the establishment and productivity of seven pasture species and all their binary mixtures. Lolium x boucheanum had the highest relative seedling vigour of the seven species. Interspecific competition was not detected in the establishment phase 127 days after sowing. The mean total grass production, after the establishment phase, for the first 14 months of the 28 treatments was 17 tonnes DM ha⁻¹. Binary mixtures produced on average two tonnes more than single sown treatments but this was not statistically significant. Interspecific competition was detected during the first year of production. The seven species had the following order of relative competitive ability: Bromus stamineus, Lolium x boucheanum, Bromus sitchensis, Dactylis glomerata, Phalaris aquatica, Festuca arundinacea, and Phleum pratensis.

The second experiment investigated the water use, water use efficiency (WUE) and Water uptake rates of five pasture grass species: Bromus sitchensis, Festuca arundinacea, Lolium x boucheanum, Phalaris aquatica, Dactylis glomerata, and seven binary mixtures from these species. There was no difference in water use between treatments over any period, and no difference in WUE over the season. In two measurement periods WUE was significant, this reflected large differences in the production of treatments for those periods. There were significant differences between the uptake rates (with no water stress) of the 12 treatments at three depths (O-20cm, 20-30, and 40-50cm). Dactylis glomerata and Dactylis glomerata mixtures with Festuca arundinacea and Phalaris aquatica had the highest water uptake rates at the 0-50cm depths.

The third experiment showed that Phalaris aquatica, Lolium x boucheanum, and Phalaris aquatic/Lolium x boucheanum could extract water to the depth of 180cm in the second year after sowing.