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The impact of differences in nitrogen content, nitrogen utilization and loss from laminae on competition between four grass species in an old pasture
Published online by Cambridge University Press: 27 March 2009
Summary
The concentration of nitrogen (N) within the emerging, youngest fully expanded and the youngest dead leaf laminae were examined in the grasses Lolium perenne, Agrostis stolonifera, Holcus lanatus and Poa trivialis in Devon, UK, in 1986 and 1987. Lamina growth, appearance interval and lamina utilization were also examined in each species. Marked tillers were measured in situ over 14–21 day periods in a continuously grazed permanent pasture under steady state management on plots receiving either zero (ON) or 400 kg nitrogen (400N) fertilizer/ha per annum. The concentration of N tended to be greatest in the distal half and least in the basal part of each lamina in each species. Total mass showed an opposite trend due in part to the shape of the lamina. Less than 40 % of the lamina N was lost through grazing either in the ON or 400N plots in the four species, except once in H. lanatus when more was lost. In absolute terms, because L. perenne and H. lanatus maintained larger and longer laminae than either A. stolonifera or P. trivialis, they lost more N through grazing. The four grass species recycled N from the senescing lamina with the same apparent efficiency; this meant that differences in lamina N concentration and carbon: nitrogen ratios were present in the dead laminae of the four species. L. perenne achieved the highest tissue growth rate per unit of N in the lamina in the ON plot, not only in comparison with the three other grasses but also compared with the 400N plot. This high N-use efficiency in L. perenne was not translated into an ability to either expand or maintain its population in the ON plot. L. perenne had a lower leaf appearance rate than the other species in both the 400N and ON plots, but this inherent characteristic of the species was particularly pronounced in the ON plot. A slower leaf appearance rate would limit the potential tillering capacity of L. perenne compared with the other species. A reduced tillering capacity, exacerbated by N deficiency, was probably the principal factor limiting the ability of L. perenne to exploit available niches in the ON pasture.
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- Crops and Soils
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- Copyright © Cambridge University Press 1996
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