Differences in the nitrogen use efficiency of perennial ryegrass varieties under simulated rotational grazing and their effects on nitrogen recovery and herbage nitrogen content

Abstract

Eight varieties of perennial ryegrass (six new varieties and two old ones) grown at five levels of applied fertilizer (100, 200, 300, 400 and 500 kg of N ha?1) were cut monthly during two growing seasons (March to October in 1997 and 1998) and their herbage dry-matter (DM) yield and nitrogen (N) content were determined. Herbage leaf content and the N content of young fully expanded leaves were also measured in 1997, and monthly recovery of applied N was determined in both the first and second harvest years by using 15N. The rank order of varieties was similar for annual yield of DM and N at all five fertilizer levels. Proportional differences between varieties in DM yield were greatest in the first cut of each year, the late-heading candidate variety Ba12151 out-yielding the old late-heading variety S23 by more than 70%. However, differences in annual DM yield were much more modest than in early spring yield, up to 10% in 1997 and up to 21% in 1998. The relatively small differences in total annual DM yield were attributed to only a small proportion of the applied N being recovered during a single regrowth period, most of the remainder becoming available for uptake in subsequent regrowth periods. There were small but highly statistically significant differences among varieties in the N content of their leaves, leaf N content being inversely related to yield of DM and N. This lends further support to the hypothesis that the metabolic cost of protein synthesis and turnover is a key factor controlling genetic variation both in leaf yield and in annual DM and N yield under frequent harvesting. Seasonal variation in herbage N content was much greater than differences among varieties in mean N content over all harvests. In May of both years at all applied fertilizer levels, herbage N content fell below the 20 g N kg?1 DM level required by productive grazing animalsPeer reviewe

The effects of strategic nitrogen fertiliser application during the cool season on perennial ryegrass-white clover pastures in the Western Cape Province 4. Selected nutritive characteristics and mineral content

“…Similar observations were reported by Eckard (1994) and Wilkins, Allen & Mytton (2000). No differences (P>0.05) in CP % between the 0 and 50 kg N ha-I application rates were found in 2000 and 2001.…”

Dual purpose wheat production with different levels of nitrogen topdressing

“…Generally, grass pastures have longer growth periods than other forage genres, and are more responsive to nitrogen fertilization (ASSMANN et al, 2004). Successive grazing in the same area with rotational grazing are mainly defined by the management of leaf area index (WILKINS et al, 2000). It can be seen (Figure 1) that the larger the LNF shorter time for a new pasture.…”

Management, production, and nutritional characteristics of cup-plant (Silphium perfoliatum) in temperate climates of southern Chile

“…From a nutritional perspective, such low protein content brings a clear limitation to potential uses of this forage species. This limited absorption of nitrogen is distinctly different from grass species, which can accumulate over 5% N at high rates of fertilization (Wilkins et al, 2000). Such a low requirement for N is however an interesting observation from an environmental viewpoint in livestock systems.…”