Differences in nitrogen uptake and marginal yield response between low and high yielding perennial ryegrass (Lolium perenne) genotypes

Abstract

Abstract Current nitrogen (N) use recommendations for perennial ryegrass (Lolium perenne) were derived from the response of historic genotypes certified or bred between 1930 and 1970. Despite significant increase in the yield of modern cultivars in seasons of lower forage growth (late spring through winter), no existing research considers the impact of this on N response functions or N uptake characteristics. In light of this a multi-year genotype by N rate trial was established. Data analysed confirms significant differences exist in the slope and intercept of genotype N response functions. Higher yielding modern cultivars had more than twice the marginal response to N of old genotypes in summer and autumn in addition they also yielded more when no N fertiliser was applied. Nitrogen uptake characteristics of higher yielding cultivars in the first winter were significantly greater than low yielding genotypes, thus they may present a different N leaching risk than older genotypes. Farm-scale implications of these preliminary findings warrants consideration once a larger dataset is available for analysis. Keywords: pasture, nitrogen fertiliser, genetic gain, N leaching, nitrogen economics