Effect of defoliation regime and nitrogen supply on the phyllochron of cocksfoot

The phyllochron of cocksfoot (Dactylis glomerata L.) was studied over a 6-week period with two levels of nitrogen supply (0 and 150 kg ha(-1)) and three cutting regimes which mimic lenient (P), severe (S) and continuous (C) grazing. The phyllochron was highest for treatment with N supply and it decreased from the P to the C defoliation regimes. During the study period, the phyllochron and the sheath length throughout the successive leaves appeared to increase, except for the C treatments. These patterns were accentuated in the case of N supply. The phyllochron could be expressed in a satisfactory way through the sheath length and the sward nitrogen status. For treatments without repeated cuts (C), a simplified model taking into account only the number of days following the cut and the sward nitrogen status was proposed. (C) Academie des Sciences/Elsevier, Paris.