The effect of nitrogen on the yield of four pasture grass species

Abstract

This research examined the morpho-physiological attributes of four pasture grass species under two nitrogen (N) treatments. The experiment was a split plot design with main plots of N+ and N- and subplots of cocksfoot (Dactylisglomerata), pasture brome (Bromusvaldivianus), perennial ryegrass (Loliumperenne) and tall fescue (Festucaarundinacea). Leaf length, leaf area and specific leaf area (SLA) decreased by 30%, 36% and 7% under N-, whereas leaf dryness (percentage dry matter) increased by 18%. Total accumulated aboveground plant dry matter (DM) yield decreased by 13% in response to the N- treatment. Chlorophyll levels, measured as SPAD units, predicted yield under N+ conditions which was also reflected in the leaf length, leaf area and SLA measurements. The findings also suggest that species with higher green DM compensated for external N reduction by utilising higher internal available N within the plant. Brome and cocksfoot, and to a lesser degree tall fescue, showed superior morphological leaf attributes under mixed N-availability and can be proposed as suitable alternatives in dryland and low nitrogen farming systems as an alternative to perennial ryegrasses.