Nitrogen studies in Lolium perenne grown for seed. II. Timing of nitrogen application

Abstract

The effects of applying nitrogen at different growth stages to S24 and S23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1971 to 1976. These varieties of ryegrass were found to be insensitive to timing of nitrogen application from apex initiation to the stage when ears first emerged. However, if nitrogen application was delayed until about 30% or more of the ears had emerged, yields were lower compared with earlier applications, this effect being significant when nitrogen was delayed until 70-80% ear emergence because of a decrease in both numbers of fertile tillers and number of seeds per unit area. No advantages were found for splitting nitrogen applications between apex initiation and ear emergence.

A Split Application Approach to Nitrogen and Growth Regulator Management for Perennial Ryegrass Seed Production

“…In Exp. The decrease in lodging as a result of the three-split NAM is consistent with a study in New Zealand where N application was delayed until heading, resulting in lower severity of lodging in perennial ryegrass (Hebblethwaite and Ivins, 1978). Greater tillering early in the growing season could lead to more fertile tillers, greater vegetative biomass, and lower HI which was observed during the 2010 growing season in our study (Table 3) (Cookson et al, 2000;Boelt and Studer, 2010).…”

“…Shorter plant height and less lodging could also result from the application of a growth regulator which would limit cell elongation caused by N fertilization (Cookson et al, 2000;Griffith et al, 1997b). The decrease in lodging as a result of the three-split NAM is consistent with a study in New Zealand where N application was delayed until heading, resulting in lower severity of lodging in perennial ryegrass (Hebblethwaite and Ivins, 1978). Our data suggest that N applied as a foliar 3-split program could be used to improve HI and limit excess vegetative growth if timed properly according to GDD and plant growth stage.…”