I. Pasture production

Abstract

Production and composition of 3 pasture types under intensive sheep grazing were measured over 7 years. All pastures were sown to a basic mixture of perennial ryegrass‐white clover ( Lolium × hybridum‐ Trifolium repens ) but 2 pastures had either paspalum ( Paspalum dilatatum ) or kikuyu grass ( Pennisetum clandestinum ) as an additional summer‐growing component. For the first 4 years (Period 1) ewe stocking rate averaged 17.6/ha. For the following 3 years, two management systems were imposed as subtreatments: ewes stocked at a uniform 19.8/ha and hoggets at a variable stocking rate related to pasture growth. Paspalum was a relatively minor component, but during Period 1 its inclusion produced DM yield increases of 12% in summer‐autumn and 6% per annum, and variability of yield among years was less. Paspalum had some competitive effect on ryegrass but negligible effect on associated white clover. When grazing pressure was increased for the following 3 years, paspalum content declined further. Pastures containing kikuyu grass had similar average yields to ryegrass‐based pasture in Period 1 when mechanical defoliation was used to check kikuyu aggression in autumn. For Period 2, this was discontinued and as a result kikuyu dominance increased markedly, white clover and total yields fell by 37% and 8% respectively below those in the control pasture, and autumn production increased at the expense of spring production.