A dairy system based on grass-white clover (GC) swards, receiving no artificial nitrogen fertilizer, was established and its physical performance compared with that of a system in which grass only (GN) swards received 350 kg N ha−1year−1. The comparison was made over 3 years using two self- contained Holstein-Friesian herds of 70 cows and replacements. Initially the stocking rate for both systems was 2.4 livestock units ha−1. Grass-clover swards were successfully established and GC herbage ensiled. Total silage yields from GC swards (t DM ha−1year1) were on average 0.87 those of GN swards. Over the three years of the study, grazed sward clover contents were maintained at an average of 25% of total dry matter production over the whole season, and followed a repeatable seasonal increase from an average of 8% in April to 37% in August. Milk yield per cow was within 0.97 of the target of 5700 1 cow−1in each year. However, in years 1 and 2, as a result of the lower herbage yield from GC swards, the level of concentrate required to achieve this was higher in the GC system. In year 3, the stocking rate of the GC unit was reduced to 1.9 livestock units ha−1and equal milk yields were achieved by the two units, with equal concentrate inputs. Although problems are perceived with the use of GC swards, this study has shown that, with appropriate management, GC swards can support a viable dairying system, providing an opportunity for minimizing the use of nitrogen fertilizer.