Early spring and late autumn response to applied nitrogen in four grasses

Abstract

The regrowth of Aberystwyth S. 23 perennial ryegrass, S. 24 perennial ryegrass, S. 59 red fescue and S. 170 tall fescue was studied in field swards, comparing four levels of applied nitrogen, for 8 weeks following a clearing cut. The clearing cuts were in midOctober, mid-February and mid-March in each of 3 years, different plots being used on each occasion.The application of N increased the number of leaf primordia, the number of unemerged leaves, the rate of leaf emergence and death, leaf blade length, width and weight, sheath length, number of leaves per unit area of ground and proportion of green tissue in total yield. The application of N had little effect on the number of leaves per tiller and tended to reduce weight per unit area of leaf blade. The increase in size, weight and number of leaf blades appeared to be major reasons for the positive effect of applied N on yield, previously reported; and the increase in sheath length contributed to the increase in proportion of yield above 4 cm. Rate of leaf extension was not closely related to yield and was more sensitive to temperature than was yield. Changes during regrowth in blade and sheath length helped to explain changes in weight per tiller, previously reported. The effects of improving weather conditions in late winter/early spring were similar to the effects of applied N: larger, heavier leaf blades, longer sheaths, a taller canopy, a lower proportion of dead material, younger leaves. The length of shoot apex per leaf primordium was relatively constant. Leaves continued to emerge, at a slow rate, in the period December-February. S. 170 had the biggest leaves, particularly in May, and the slowest rate of leaf turnover. Rate of leaf extension was increased by applied N more, on average, in the ryegrasses than in the fescues.indirectly, with grassland management to develop a fuller understanding of reasons for yield differIn an earlier paper (Wiknan, 1980) a field experi-ences so that management decisions can be more ment concerned with early spring and late autumn soundly based, response to applied nitrogen in four grasses was described and the results for yield, number of tillers EXPERIMENTAL PROCEDURE and chemical composition presented and discussed. In the same experiment leaf initiation, rates of leafThe experimental treatments, field procedures emergence and extension, leaf blade area and weight, and weather have been described previously sheath length and proportion of green tissue in total (Wilman, 1980). Regrowth after a cut in field swards yield were studied in order to gain a more com-of grass sown as pure stands was studied for 8 weeks plete view of the effects of applied N, grass species at three times of year in each of 3 years, using and variety, stage of regrowth, time of year and different plots on each occasion. All combinations weather. The two papers together present a much of four levels of applied N and four grasses were more comprehensive set of data on this topic, for compared. A randomized-block design was used, early spring and la...

The effects of rate and timing of application of fertilizer nitrogen in late summer on herbage mass and chemical composition of perennial ryegrass swards over the winter period in Northern Ireland

“…The mean apparent recovery of N (calculated from the data in Tables 2 and 4) was 0·50, 0·40 and 0·38 for 30, 60 and 90 kg N ha −1 , respectively, which is lower than the 0·69, 0·37 and 0·48 found after a 7‐ to 8‐week regrowth interval by Wilman (1980) for 42, 84 and 126 kg N ha −1 applied in October. Further studies are required to fully quantify the sources of N loss after N application in late summer.…”

“…In agreement with evidence from the literature, the DM content of the herbage decreased and N concentration increased with increasing rate of N application (Baker et al ., 1961a; Wilson and Flynn, 1979; Wilman, 1980). Similarly, progressively reducing the length of the regrowth period reduced the DM content and increased the N concentration of the herbage.…”

Comparaison des dynamiques d'apparition et de mortalité des organes de fétuque élevée, dactyle et luzerne (feuilles, talles et tiges)

“…La densité de talles peut augmenter jusqu'à des valeurs d'indice foliaire de 3-4, qui correspondent au seuil à partir duquel la compétition pour la lumière devient prépondérante (Simon et Lemaire, 1987 (Ong, 1978 (Sato, 1971). Le nombre de tiges diminue rapidement au cours d'une repousse (Woodward et Sheehy, 1979), et ce sont généralement les tiges les plus petites qui meurent (Duru et Langlet, 1988 (Dufour et al, 1989 (Wilman et Mohamed, 1980), nous l'avons contrôlé à partir du calcul d'un indice de nutrition (Duru, 1992 (Yu et al, 1975), 240 à 265 °C.j pour de la fétuque en plein champ en hiver (Lemaire, 1985). Ces valeurs moyennes reflètent cependant une forte variabilité entre périodes de croissance et au cours de celles-ci.…”

Nutrient Pools in Bermudagrass Swards Fertilized at Different Nitrogen Levels

“…Increasing N fertilization level has been reported to increase herbage growth rate, tiller density, height (Wilman, 1980), and ultimately herbage accumulation. Herbage accumulation increased linearly (P = 0.02) from 8.6 to 9.7 Mg ha −1 yr −1 as N fertilization level increased from 50 to 250 kg ha −1 yr −1 .…”