Resident ryegrass in hill country pastures

Abstract

The attributes of 1800 ryegrass plants removed from North Island hill country aredescribed and the implications for oversowing discussed. Morphology was varied but the mean of the population was prostrate and densely tillered, resulting in dense pastures under intensive grazing. Although morphology was not related to the site of plant origin, agronomic response to low nitrogen and moisture stress was. Plants from north-facing steep areas responded least to application of nitrogen or water indicating a low relative growth rate. A probable survival mechanism for moisture-stressed plants is reduced vegetative growth and increased seed set. Response to moisture stress was found to be heritable. In moderate-high fertility steep sites total ryegrass production has not increased after oversowing new cultivars. It is assumed that this is a reflection of the number of niches available for ryegrass exploitation. Our studies show that the strength of existing ryegrass is its genetic diversity and its ability to exploit the various niches present in hill country. The growth and expansion of these ryegfass populations should be actively encouraged. In niches below the optimum for rycgrass growth new species should be introduced. Keywords hill country, perennial ryegrass, morphology, stress, genetics, oversowing, management