Production of two species and two interspecific hybrids of phalaris under irrigation in south-west New South Wales

Abstract

Two phalaris hybrids (Siro 11 46 and allopolyploid) and the parent lines (Phalaris aquatica and P. arundinacea) were compared in monoculture with nitrogen fertilizer and in a mixed sward with white clover and lucerne. The experiment was flood irrigated and the effects of defoliating the swards at intervals of 21, 42 and 84 days were measured. The hybrid (Siro 11 46) was the most productive genotype at all defoliation intervals. Eighty one % of its annual yield occurred in spring and summer. This production imbalance renders Siro 11 46 unsuitable as the foundation of a pasture for high production throughout the year. The mixed sward produced more than the monoculture sward when defoliated every 21 or 42 days and there was increased production associated with increased defoliation interval. The monoculture sward was more productive than the mixed sward at an 84 day defoliation interval. The yield of Siro 1146 + white clover was 2.25 t ha-1 per 84 days, compared with a mean yield of phalaris + white clover of 1.78 t ha-1 per 84 days for the three other genotypes. The results indicate that Siro 11 46 grown with white clover and defoliated approximately every 42 days would be a suitable alternative pasture to Paspalum dilatatum and white clover in the two-pasture system used in irrigation areas of southern New South Wales. The problems of low acceptability and suspected toxicity of Siro 1146 are discussed.