The nitrogen handling characteristics of white clover (Trifolium repens L.) cultivars and a perennial ryegrass (Lolium perenne L.) cultivar

G. S. Griffith, A. Cresswell, Debra Allen

Allbwn ymchwil: Cyfraniad at gyfnodolynErthygladolygiad gan gymheiriaid

16 Dyfyniadau (Scopus)

Crynodeb

Ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) have contrasting responses to soil mineral N availability and clover has the ability to fix atmospheric N 2 symbiotically. It has been hypothesized that these differences are the key to understanding grass-clover coexistence and vegetative dynamics in pastures. However, the whole plant response of clover and ryegrass to mineral N availability has not been fully characterized and inter-cultivar variability in the N-handling dynamics of clover has not been assessed. A detailed experimental study to address these issues was undertaken. For all clover cultivars and ryegrass, mass specific mineral N uptake rates (of whole plants) were similar saturating functions of mineral N availability. For all clover cultivars total N assimilation rates, whole plant C:N ratios and root:shoot ratios were independent of mineral N availability. Clover growth rates were also independent of mineral N availability except for a slight (<10%) reduction at very low N availability levels. Specific N 2 fixation rate (whole plant) was precisely controlled to ensure fixation balanced the deficit between mineral N uptake and the total N assimilation required to maintain constant whole plant C:N ratio. There was always a deficit between N uptake and the total N assimilation required to maintain C:N ratio. Consequently, some N 2 fixation remained engaged even at high mineral N availability levels. All inter-cultivar variation in N 2 fixation dynamics could be attributed to variations in growth rate. Clover mass specific growth rate declined as plant size increased. Ryegrass specific growth rate, whole plant C:N ratio and root:shoot ratio were dependent on N availability. Increased N availability led to increased growth rate and decreased C:N and root:shoot ratios. Specific growth rate was also dependent on plant size, growth rate declining as plant size increased. It is concluded that clover inter-cultivar variation in field performance is unlikely to be a consequence of variation in N-handling characteristics. Inter-cultivar differences in growth rate are likely to be a much more important source of variation.

Iaith wreiddiolSaesneg
Tudalennau (o-i)1879-1892
Nifer y tudalennau14
CyfnodolynJournal of Experimental Botany
Cyfrol51
Rhif cyhoeddi352
Dynodwyr Gwrthrych Digidol (DOIs)
StatwsCyhoeddwyd - Tach 2000

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