The establishment and performance of a dairy system based an perennial ryegrass - White clover swards compared with a system based on nitrogen fertilized grass

A dairy system based on grass-white clover (GC) swards, receiving no artifi cial nitrogen fertilizer, was established and its physical performance comp ared with that of a system in which grass only (GN) swards received 350 kg N ha(-1) year(-1). The comparison wits made over 3 years using two self-con tained Holstein-Friesian herds of 70 cows and replacements. initially the s tocking rate for both systems was 2.4 livestock units ha(-1). Grass-clover swards were successfully established and GC herbage ensiled. Total silage y ields from GC swards (t DM ha(-1) year(-1)) were on average 0.87 those of G N swards. Over the three years of the study, grazed sward clover contents w ere 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 l cow(-1) in each year. However, in years 1 and 2, as a resu lt of the lower herbage yield from GC swards, the level of concentrate requ ired to achieve this was higher in the GC system. In year 3, the stocking r ate of the GC unit was reduced to 1.9 livestock units ha(-1) and equal milk yields were achieved by the two units, with equal concentrate inputs. Alth ough 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 fertil izer.