Journal of Experimental Botany, Vol. 53, No. 366, pp. 111-121,
January 2002
© 2002 Oxford University Press
Original Papers |
Influence of summer sowing dates, N fertilization and irrigation on autumn VSP accumulation and dynamics of spring regrowth in alfalfa (Medicago sativa L.)
1 INRA, Unité d' Agronomie de Châlons-Reims, BP 224, 51686 Reims cedex 2, France
2 UMR INRA–UCBN Physiologie et Biochimie Végétales, Institut de Recherche en Biologie Appliquée, Université, 14032 Caen Cedex, France
3 Station d' Ecophysiologie des Plantes Fourragères, INRA, 86600 Lusignan, France
4 Department of Agronomy, Purdue University, West Lafayette, IN 47907-1150, USA
Herbage yield of alfalfa (Medicago sativa L.) depends on forage management or environmental conditions that change C and N resource acquisition, and endogenous plants factors such as root organic reserves and number of active meristems. The aim of this work is to study the influence of two sowing dates in summer (12 July or 9 August), N fertilization (0 or 100 kg ha-1) and/or irrigation applied during the first year of alfalfa establishment on (i) the accumulation of N organic reserves (soluble proteins and more specifically vegetative storage protein) in taproots during autumn, (ii) the number of crown axillary meristems present at the end of winter and (iii) the dynamics of spring shoot growth. Delaying the sowing date for one month reduced root growth and root N storage, especially vegetative storage proteins (VSP) during autumn. Irrespective of sowing dates, N fertilization did not affect root biomass, number of crown buds, total root N, root soluble protein or VSP concentrations. By contrast, water deficiency during alfalfa establishment in the early summer reduced both root growth and N reserve accumulation. When spring growth resumed, there is a significant linear relationship between leaf area development and soluble protein and VSP concentrations in taproots, and also the number of crown buds. The results showed that an early sowing date and adequate water status during the summer allowed alfalfa plants to accumulate N reserves by increasing taproot mass and soluble protein concentrations, especially VSPs. This resulted in rapid shoot regrowth rates the following spring.
Key words: Alfalfa, spring growth, sowing date, N fertilization, water, VSP.
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