Performance of several subtropical grasses in Northland hill pastures

Abstract

Five C4 grasses [Pennisetum clandestinum (kikuyu); Cynodon dactylon cv. Coastcross 1; Digitaria eriantha spp. pentzii (pangola); D. pentzii (CQ911); Setaria sphacelata cv. Narok] were evaluated as components of three hill country pastures in Northland, New Zealand (lat. 34°S). Best site for all C4 grasses was a west-facing slope grazed by cattle and the most competitive species was kikuyu. After 4 years it occupied 2.5 times the area and had 5 times the herbage mass of the second most competitive species (‘Coastcross 1’). its rate of spread into resident pasture averaging 8, 11, and 21 cm/year. Under mowing, with two rates of nitrogen (N) fertiliser over summer (N0, N200 units), the control sward yielded 7.8 and 10.1 t herbage DM/ha per year on one site. Relative yields of swards with C4 grasses added were 2–138% for NO and 135–152% for N200, although stem/stolon material of C4 grasses accounted for 18–54% of total yield. Whole sward DM digestibilities were little affected by N rate, were higher in the cool than the warm season (63.5, 53.5%), and varied among sward types from 55 to61% (pangola, control). Efficiencies of sward N use in summer were 11.6–37.3 kg DM/kg N (control, ‘Narok’). It was concluded that kikuyu is easily the best adapted of the C4 grasses screened, and that to realise the summer potential of improved C4 grasses as hill pasture components, both N fertiliser and greater grazing control would be needed, especially for bunch grasses such as ‘Narok’.

Keywords:

• hill pasture
• C4 grasses
• Pennisetum clandestinum
• kikuyu
• Cynodon dactylon cv. Coastcross 1
• Digitaria eriantha spp. pentzii
• pangola
• Digitaria pentzii
• CQ911
• Setaria sphacelata cv. Narok
• subtropical grasses
• ‘Narok’
• ‘Coastcross 1’