Division of Tropical Crops and Pastures, CSIRO Davies Laboratory, Private Mail Bag, P.O. Aitkenvale, Qld. 4814.
Pastures of Narok setaria (Setaria sphacelata var. sericea cv. Narok) and of Samford Rhodes grass (Chloris gayana cv. Samford) fertilised with 250 kg single superphosphate, 125 kg KG and 336 kg N/ha/yr were compared at a set stocking regime of 5 steers/ha over a 4-year period.
Pastures of Narok gave higher yields of total pasture dry matter and of green dry matter on most sampling occasions.
The N, P and K concentrations in the yield on offer were similar for both pastures, although N in the Samford Rhodes grass was higher than for Narok in summer/autumn. Over this period, however, samples plucked to simulate herbage grazed by cattle were significantly higher in N and K for the Narok pastures. Faecal N levels were also higher for steers grazing Narok throughout the year. Plucked pasture samples of Narok in spring, summer and autumn were higher in N, K, Na and Zn whereas those of Samford Rhodes grass were higher in Ca and S.
Despite differences in yield and mineral concentration the pattern of weight gain of steers was similar for both pastures in 3 of the 4 years although Narok tended to give reduced weight loss in winter and spring with Samford giving better weight gain in summer/autumn. The marked superiority of Narok over the winter/spring period of 1970 was associated with an exceptionally cold winter which retarded the spring growth of Samford Rhodes grass. However, annual liveweight gains did not differ significantly in any year. Mean gains per annum were 160 and 159 kg/head for Narok and Samford respectively.
Possible reasons for the lack of difference in animal gain on the 2 pastures are discussed.