Changes in pastoral farming practices and pasture persistence - a review

Abstract

From 1990 to 2010 there have been major changes in New Zealand pastoral agriculture. The intensification of the dairy industry has led to higher stocking rates, lower grazing residual DM, higher N fertiliser use and increased supplementation. However, there is little evidence that these changes are responsible for the decreased persistence of ryegrass-based pastures, rather the interactions between low summer rainfall, low water-holding capacity soils, endophyte status and cultivar 'type' have caused significant pasture damage. These factors, together with plant nutrient status (especially N) and plant population survival mechanisms (tiller dormancy, birth and death rates, seed production and establishment) are hypothesised to be the primary drivers of ryegrass persistence. A secondary subset of pests, diseases, weeds and high grazing intensity (pugging and pasture 'pulling') are considered to interact with the primary drivers to compromise ryegrass tiller survival. Attention to plant species and cultivar selection, tiller replacement mechanisms and ryegrass cultivar development are required to improve ryegrass persistence. Keywords: climate, dairy, N fertiliser, perennial ryegrass, white clover