INFLUENCE DE LA HAUTEUR ET DE LA FREQUENCE DES COUPES SUR LE RENDEMENT, LE PEUPLEMENT, LA COMPOSITION CHIMIQUE ET LES RESERVES NUTRITIVES DE LA LUZERNE
A 3-yr study on height and frequency of cutting showed that alfalfa (Medicago sativa L.) cut at 5 cm from the soil produced significantly more dry matter per hectare than that harvested at 10 cm, but the differences between the two heights decreased with the years and the frequency of cutting. Forages cut at either height had similar mineral composition at any one cutting. However, the percentages of cell walls and of lignocellulose were, in general, highest in alfalfa cut at 5 cm. Height of cutting did not affect the stand nor the accumulation of food reserves in the roots in the fall. The two-cut system gave a uniform production from year to year and maintained the stand at a high level. The three-cut system, the last cut taken in October, yielded the highest yields of dry matter and of crude protein while the four-cut system produced the least and had the thinnest stand at the end of the experiment. Frequency of cutting gave rise to significant variations in the chemical composition of the forages, variations resulting from the difference in the stages of growth at harvest. In general, alfalfa cut at a younger stage exhibited a more valuable composition than that harvested at a later stage. Food storage in the roots varied with frequencies, being highest with the two-cut system and lowest with the four-cut system.Key words: Alfalfa, height and frequency of cutting, yield, chemical composition, food reserves