The influence of applied nitrogen on herbage yield and quality of Lolium perenne L. pastures during the establishment year under subtropical conditions

Abstract

The dry matter (DM) yield, cellulase DM disappearance (CDMD) and herbage nitrogen (N) of sheep-grazed perennial ryegrass [Lolium perenne (L.)] during its establishment year was evaluated. Yield and quality were monitored under N applications ranging from 120 to 720 kg N ha⁻¹ a⁻¹. Total (perennial ryegrass and weeds) and perennial ryegrass DM yields increased with increasing levels of N up to 480 kg ha⁻¹ a⁻¹. Conversely, weed DM yields declined with increasing N up to 480 kg ha⁻¹ a⁻¹. A logistic model predicting the response of perennial ryegrass DM yield to applied N also indicated little justification for applying N in excess of 500 kg ha⁻¹ a⁻¹. Although CDMD and herbage N increased throughout the range of N applied, such increase was significant (P < 0.05) only up to 480 kg ha⁻¹ a⁻¹. In terms of yield and quality, there is little justification for applying N in excess of 480 kg ha⁻¹ a⁻¹ to perennial ryegrass during its establishment year.