Influence de l'indice foliaire et des réserves en hydrates de carbone au moment de la coupe sur la croissance foliaire de deux graminées fourragères (Dactylis glomerata L. et Festuca arundinacea Schreb.)

Abstract

Leaf growth of two forage grasses (Dactylis glomerata L. and Festuca arundinacea Schreb.) was studied as a function of the sward state after a cut. Two heights of cut (3 and 6 cm) and a variable number of previous cuts were used to reach different residual leaf area index (IFr), and non-structural carbohydrate (CNS) concentration and quantity. For both species, four treatments were studied in 2 consecutive years. In mid-May for each of the species, the IFr ranged from 0 to 1, and the quantity of CNS varied from 12 to 25 g 100 g−1 DM according to the treatments. Over the 3 wk of regrowth, the IF reached values ranging from 1 to 7 and its increase depended on the IFr and the quantity of CNS. Among the three components of the quantity of CNS (weight of sheath per tiller, tiller density and CNS concentration), only the first two had a significant effect on the IF increase. Tiller mortality occurred when the quantity of CNS or the IFr were the lowest and it contributed little to the growth of lower leaves. No significant differences were found between the two species. Key words: carbohydrates, leaf area index, tiller, cut