Incidence of sowing date, fertilization and irrigation practices on establishment of a legume-grass mixed pasture

In an experiment conducted during 1997 and 1998 at the Experimental Farm of the Faculty of Agricultural Sciences (University of Rosario) the combined effects of three factors on the establishment of a pasture of alfalfa (Medicago sativa L.) and tall fescue (Festuca arundinacea Schreb.) were studied. The treatments combined presence or absence of complementary irrigation, with or without corrective fertilization at three sowing dates (early, normal and late), corresponding to a split-split plot factorial design with three replicates. The number of plants and the aerial biomass of both species and the number of tillers of tall fescue were measured. Data were analyzed using ANOVA and Tukey Test. A marked effect of climatic conditions on variables that define pasture productivity was demonstrated. Fertilization increased number of tillers and forage production of tall fescue without influencing the alfalfa. Irrigation had a positive effect on the density of alfalfa, but no effect on tall fescue. During years with weather conditions similar to those of this experiment, a more favorable proportion of aerial biomass between the two species can be expected from sowing in April.