Manfredi, Córdoba, Argentina

In Argentina, there are approximately 6 million ha of alfalfa (pure or in mixtures with temperate grasses). About 85% of that area is used under direct grazing for beef an dairy production. However, within the Argentine cultivar evaluation system, performance of new alfalfa cultivars is evaluated mainly under cutting conditions. In some locations, only the best materials under cutting are further tested under rotational grazing. Simultaneous evaluation under both management systems has never been performed.

The objective of this paper was to simultaneously evaluate forage yield, and persistence of 12 alfalfa cultivars under cutting and grazing conditions. The experiment was conducted at Manfredi Exp. Stn.-INTA, Cordoba, Argentina. Tested materials included 6 cultivars from the intermediate fall dormancy group (DK 170, Victoria SP INTA, Sutter, 5683, 5715 and GT 13 R Plus) and 6 from the non-dormant group (Alfa 200, Super Lechera, Falcon, 5939, DK 189, and Monarca SP INTA). Trail was conduted for three growing seasons (1996/97 to 1998/99).

The varieties were planted in April, 1996 in 800 m² plots. The experiment was a 12*2 factorial arranged as completely randomized design with 2 replicates. Cut or grazing was performed at 10% blooming. Length of grazing was about 7 days and frequency of grazing was adjusted to forage growing rate. Alfalfa production (Mg DM ha^-1 under both cutting and grazing systems was estimated by cutting 5 randomized samples prior to each harvest. Persistence (%) was calculated as the relationship of stand cover between the beginning and the end of the experiment. An analysis of variance for yield and persistence was performed for both management system. Performarce of each cultivar within and between management systems was compared by orthogonal contrasts.

Along the experiment there was an important soil moisture stress, causing yields lower than normal for the area. Average accumulative forage production (three growing seasons) under cutting and grazing was 21.7 Mg DM ha^-1 and 21.6 Mg DM ha^-1, respectively. There was no cultivar*management system interaction. Under cutting, most productive cultivars were Victoria SP INTA, 5683 and 5715, while under grazing were Falcon and Monarca SP INTA.

In terms of persitence, there was no interaction between cultivar and management systems. As a general trend, persistence of intermediate dormant cultivars was higher (70%) than that non-dormant varieties (65%) under both cutting and grazing systems.

We concluded there was no effect of utilization system on yield and persistence of the tested intermediate and non-dormant alfalfa varieties.