Producción primaria y sobrevivencia estival de la mezcla forrajera Festuca arundinacea, Trifolium repens, Lotus corniculatus en su primer año bajo combinaciones de frecuencia e intensidad de pastoreo contrastantes

In Uruguay, animal production is largely based on pasture-based systems, where grazing management plays a key role in determining pasture productivity and persistence. The objective was to evaluate the effect of contrasting combinations of grazing frequency and intensity on forage production, botanical composition, and tiller survival of a forage mixture composed of Festuca arundinacea, Trifolium repens, and Lotus corniculatus during its first year of establishment. The experiment was conducted at the Estación Experimental “Dr. Mario A. Cassinoni” (Paysandú, Uruguay) between August 2022 and May 2023, using a randomised complete block design with a 2 × 2 factorial arrangement, combining two defoliation frequencies (two and four leaves on Festuca arundinacea) and two grazing intensities (30% and 70% residual forage), with four replicates. Results showed that during the first evaluation period (winter–spring), the lower defoliation frequency (four leaves) significantly enhanced pasture production and growth rate, regardless of grazing intensity. However, in subsequent periods, differences among treatments were reduced, mainly due to the pronounced water deficit recorded during spring and summer, which limited the potential growth of the pasture. Grazing intensity had a minor effect on forage production, with differences observed primarily in residual forage during the summer–autumn period. Botanical composition exhibited marked seasonal variation, with a greater contribution of legumes in summer, associated with the summer growth pattern of Lotus corniculatus, and a predominance of Festuca arundinacea in autumn. Species responses to grazing management were differential: tall fescue was favoured by more frequent grazing, white clover by less frequent and more intense defoliation, and lotus by low grazing intensity. Tiller density declined significantly toward autumn, with no differences among treatments. In conclusion, lower grazing frequency and intensity favoured the initial productivity of the forage mixture; however, management effects were strongly conditioned by environmental factors. These results highlight the importance of adjusting grazing strategies according to climatic conditions to improve the productivity and persistence of perennial pastures in Uruguayan grazing systems.