Agronomic variability in white clover varieties under differing nitrogen application rates

White clover (Trifolium repens, L.) incorporation into pasture based ruminant production systems has the potential to increase their economic and environmental sustainability. Varieties of white clover are evaluated in national recommended list evaluation trials to identify the best varieties to sow on commercial farms. This highlights the need for recommendations to have a broad applicability. In this study, 17 clover varieties were examined under different nitrogen (N) levels to determine whether varieties re-rank in their agronomic characteristics and how sensitive they are to the imposed management. The clover varieties were sown with perennial ryegrass (Lolium perenne L.; PRG) along with a PRG monoculture control in a factorial plot study with three different N rates (0 kg N/ha, 75 kg N/ha and 150 kg N/ha). The experiment was carried out for two years, following an establishment year, measuring sward herbage yield, clover content and nutritive quality. The expected inverse relationship between N rate and clover content in the sward (r = −0.55) and positive correlation between N rate and herbage production (r = 0.38), were both observed. There was, however, a significant variety × N interaction, with a re-ranking of varieties between N application rates for both traits. The re-ranking of these clover varieties between N management systems indicated that the current evaluation of varieties under a single rate of N is not optimal to identify elite varieties for different farm management systems. This study outlines the need to design more effective and widely applicable testing schemes under varying N management systems to accurately define the agronomic potential of individual varieties, across a wider range of farming conditions. The identification of elite white clover varieties under varying N application rates will assist farmers in selecting varieties to reach both environmental mitigation and herbage production targets under their specific grassland management system.