The Chemical Composition of a Range of Forage Grasses Grown Under Two Nitrogen Fertiliser Inputs and Harvested at Different Stages of Maturity

Abstract

Grass species, rate of N fertiliser application and plant maturity at harvest represent three of the most important grassland management factors affecting plant chemical composition. This study investigates the effects of two N fertiliser inputs and five harvesting dates in the primary growth on the yield and chemical composition of five common grass species. Perennial ryegrass, Italian ryegrass, cocksfoot, timothy and tall fescue, were grown in triplicate field plots under two inorganic nitrogen fertiliser inputs (low = 0 kg N ha-1, high = 125 kg N ha-1) and harvested at five sequential dates (fortnightly from 12 May–7 July; Harvests 1–5) in the primary growth in both 2009 and 2010. At each harvest date, herbage was weighed to estimate DM yield and representative samples were used to determine herbage chemical composition. In general for the five grass species investigated, herbage dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) concentrations increased (P 0.05) was observed between the other grass species. Although timothy and PRG had a similarly high DMD, of the five grass species timothy had the highest (P < 0.001) NDF and ADF concentration. The IRG had the highest (P < 0.001) WSC concentration and lowest (P < 0.001) BC making it the most suitable species for ensiling.