Spring Nitrogen Rate and Timing Influence on Seed Yield Components of Perennial Ryegrass

Abstract

Spring application of N generally increases seed yield of perennial ryegrass (Lolium perenne L.). Understanding the influence of N rates and timings on seed yield components can be used to improve N use efficiencies and seed yield. Field experiments during 1982 and 1983 at Oregon State University studied the effects of 60, 90, and 120 kg N ha−1, applied either at double‐ridge stage (DR) or at spikelet initiation stage (SI), on seed yield and yield components of the cultivar Pennfine. Control plots with no spring‐applied N were also included. Little lodging was observed in 1982, but all plots severely lodged by maturity in 1983. Timing of N application did not affect seed yield in either year. Compared with the control, spring N increased seed yield 43% in 1982 and 39% in 1983 when averaged across rates. In 1982, seed yield did not vary with N rates applied at DR, but 120 kg N ha−1 produced greater seed yield than 60 kg N ha−1 when applied at SI. In 1983, seed yield was maximized by 90 kg N ha−1 applied at DR, and by 120 kg N ha−1 applied at SI. Nitrogen application did not affect the number of spikes per unit area, but increased seed number per spike in 1982 and weight per seed in 1983. Averaged across rates and timings, N increased total number of seeds produced per unit area 43% in 1982 and 30% in 1983. Seed yield was correlated with the number of seeds per spike in both 1982 (r2 = 0.68) and 1983 (r2 = 0.72). In 1983, seed yield was also correlated with weight per seed (r2 = 0.55). We concluded that in the absence of severe lodging, 60 kg N ha−1 applied at DR is adequate for achieving maximum seed yield. If fertilization is postponed until SI, however, higher rates of N may be required. Results also suggest that modifications in N fertilization should focus on improving seed set per spike and seed growth rather than increasing the number of spikes per unit area or floret sites per spike.

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

“…Significant N loss due to volatilization and denitrification can also occur when large amounts of N are applied as a single application (Burt et al, 1993;Cookson et al, 2001). Applying N to match perennial ryegrass N demands during the growing season rather than single large applications could improve seed yields (Young et al, 1996;Kurcinka, 2009), improve seed quality (Cookson et al, 2000;Young et al, 1996), and potentially reduce environmental impacts of N fertilization by mitigating N loss (Cookson et al, 2000;Mullen et al, 2003).…”

Uptake and Distribution of Nitrogen in Perennial Ryegrass: Effect of Additional Applications at Vegetative Growth

“…If the application Table 1. [9,11,12] In our experiment, a distinct difference in shoot number, dry matter accumulation, and N content was found in the low-N and high-N treatments at the start of the experimental period (Table 1, Figs. changes N content and=or the biomass production, the original N rate is defined as insufficient for optimal growth, whereas if plants did not respond to an additional application, the original N rate was considered as sufficient.…”

“…[9][10][11][12] In addition, late application in plants with sufficient N available will cause increased growth of vegetative tillers [13] as well as early and strong lodging that can be detrimental for the seed yield. [9][10][11][12] In addition, late application in plants with sufficient N available will cause increased growth of vegetative tillers [13] as well as early and strong lodging that can be detrimental for the seed yield.…”

Seeding Rate, Row Spacing, and Nitrogen Rate Effects on Perennial Ryegrass Seed Production

“…Although the effect of N rate on seed yield sometimes depended on the SR, applying N at a rate of 157 kg ha −1 (even in combination with the lowest SRs) always resulted in seed yields equivalent to the top-yielding treatments (P < 0.05, Table 7). Previous research has shown that increased N availability can improve the number of seeds set per spike in perennial ryegrass, which is a primary factor driving seed yield (Young et al, 1996). Previous research has shown that increased N availability can improve the number of seeds set per spike in perennial ryegrass, which is a primary factor driving seed yield (Young et al, 1996).…”

“…The effect of row spacing on yield and agronomic characteristics of perennial ryegrass in Minnesota has not been well characterized. Studies evaluating the effect of row spacing in various grass seed crops in China indicated that the number of seeds per spikelet, an important seed yield component (Young et al, 1996), increased with row spacing and that TSW for both Chinese sheepgrass (Leymus chinensis Trin. This can increase within-row tiller density, and the resulting increased plant-to-plant competition for light and nutrients in more densely planted rows could have an effect on plant growth (Kays and Harper, 1974;Deleuran et al, 2009;Han et al, 2013).…”