Efecto de tres regímenes de cosecha en el comportamiento productivo de cinco variedades comerciales de alfalfa (Medicago sativa l.)

The effect of three harvest systems on the productive behaviour of five commercial alfalfa cultivars was studied at Montecillo,Texcoco, Mexico. Clippings were performed each four, five or six weeks in spring and summer, fall and winter, respectively. Dry matter per clipping (YDM) and total accumulated dry matter (YTADM) was greater in the Oaxaca, San Miguel and Moapa varieties than in Valenciana and Cuf-101, Oaxaca showed its greater YDM on August, February and March, and Moapa on October and January, Moapa, Oaxaca and San Miguel had greater YTADM than Valenciana and Cuf-101 for the period of the experiment. Seasonal yield of accumulated dry matter (SYADM) was higher in summer (31 %) than spring (27 %), fall (22 %) or winter (20 %), San Miguel and Oaxaca presented higher SYADM than Valenciana and Cuf-101 in summer, fall, winter and spring, and Moapa had greater SYADM than Valenciana and Cuf-101 in summer, fall and winter. Leaf:stem ratio (L:S) was higher in winter (0.83) than spring (0.75), summer (0.77) and fall (0.72), Valenciana (0.99) and Cuf-101 (0.82) had greater L:S than San Miguel (0.72), Oaxaca (0.73) and Moapa (0.70). Leaf appearance rate diminished from the third regrowth week onwards. The greater forage productivity observed in summer and spring in respect of fall and winter shows the productivity potential that may be exploited when the type of variety and environmental conditions are considered to maximize forage availability throughout the year.