Effects of early spring N-fertilisation strategies on grass production and nitrogen recovery

Application rate and application date of fertiliser nitrogen (N) are important factors determining grass production response and N recovery by grassland in spring. This study was conducted at two sites with different soil types (sandy loam and clay loam) in Ireland in spring 2005 and 2006. In comparison with a non-fertilised (zero-N) control, urea N was applied at rates of 60 and 90 kg N/ha either as single or split applications on eight dates ranging between 11 January and 14 March. Grass was harvested on four occasions between 21 February and 25 April. Split fertiliser N applications provided the best outcome in relation to grass DM production, apparent recovery of fertiliser N (ARFN) and cost of additional grass produced compared with single applications. Likewise, in this study the optimum date to commence fertiliser N application was 21 January combined with a second application on 26 February in terms of the cost-effectiveness of the fertiliser N input to increase grass DM production.