Limitations to production and choice of species in finishing pastures

During the past 15 years many new pasture species and cultivars have been released and are now commercially available. However, with the exception of Nui and Ellett ryegrasses, only a few have received enthusiastic acceptance by farmers. Acceptance depends in part to the extent to which the new plant can overcome periods of low productivity. Other reasons which are the frequent subject of comment by seed merchants include historic use of a pasture mixture and seed cost. In the summer-moist regions of New Zealand, perennial ryegrass and white clover are traditionally used. During favourable seasons, production from these pastures is adequate for finishing stock. However, periodic summer droughts and low winter temperatures can create problems for farmers, particularly under high stocking rates. Temperature and water are the two most important environmental factors determining total and seasonal pasture productivity and influencing the use of pasture plants. Changes in these factors are the major cause of annual variation in production between seasons and years. They can influence plant performance as components of weather or by association with soil physical characteristics. We will describe limitations imposed by temperature and moisture on pasture plants in the finishing country of Southland and Manawatu and, where appropriate, comment on choice of species. There are obviously other areas in New Zealand where the effects described also operate. Southland has a livestock industry based almost exclusively on sheep for lamb meat and wool. The major pasture restriction is in winter and early spring when growth rates do not meet animal requirements. The farming pattern of the Manawatu is more complex, with enterprises based on sheep, beef and