Resumen

KLOSTER, A.M.  y  ZURBRIGGEN, G.. Producción y persistencia de una mezcla de alfalfa (Medicago sativa L.) y festuca alta (Festuca arundinacea Schreb.) bajo intensidades y frecuencias de pastoreo contrastantes. RIA. Rev. investig. agropecu. [online]. 2019, vol.45, n.1, pp.44-51. ISSN 1669-2314.

The mixture of alfalfa (Medicago sativa L.) and tall fescue (Festuca arundinacea Schreb.) is widely adopted in the Pampas Region due to its good productivity and complementarity. However, the management of the frequency and intensity of defoliation is critical in order to maintain a stable balance between species. The objectives of this work were to analyze the production and persistence of the mixture under different frequencies and intensities of grazing, and to identify strategies that might improve the autumn-winter fescue production. The experimental work was carried out at the EEA INTA Marcos Juárez (Córdoba, Argentina), on a typical argiudol soil, without limitations. The pasture, sown with 10 kg of alfalfa and 8 kg of tall fescue per hectare, received during 23 months four treatments resulting from the combination of two intensities (I) and two frequencies (F) of grazing, with three plot replications. The I were allowances of 34.5 and 23.0 g DM.kg-1 of l.w. for I1 and I2 respectively and the thermal sums of 350°Cd and 450°Cd were F1 and F2. The combinations I2/F1; I1/F1; I2/F2 and I1/F2 conformed I+F+, I-F+, I+F- and I-F-, respectively. A put and take grazing system of 7 days of occupation was performed and the pre and post grazing biomass was estimated by 10 manual cuts, with species separation. The intake of DM.ha-1 of each component was calculated for autumn-winter (AW) and spring-summer (SS) grazing seasons. Basal cover (BC) was estimated in autumn of each year using a metal reticule on transects with six observation stations. SAS GLM was used for statistical analysis. During AW, alfalfa biomass was higher in I+F- and I-F- for both cycles. For tall fescue, the highest biomass was reached in I-F+, and the lowest alfalfa/fescue ratios were in I+F+ and I-F+. Regarding intake.ha-1, in AW, differences were detected for alfalfa in favor of I+F-, but not for tall fescue (p=0.27) or the mixture (p=0.12). During SS, the biomass of fescue was higher in I-F+ for both cycles. Although for alfalfa no differences were observed in the second cycle, I-F- was higher during the whole period. In intake.ha-1, there were differences in favor of I+F+ for alfalfa and the mixture, whereas fescue did not show differences between I+F+, I-F+ and I+F-; however, I-F- values were lower than the others. For the whole period considering both seasons, intake.ha-1 was higher in I+F+ (p<0.01). In regards to BC, there were differences for alfalfa early in the first year, with the lowest values ​​for I+F+ and I-F+ (p=0.03). On the other hand, for tall fescue, differences appeared at the end of the period, I-F+ overcoming I+F- (p<0.01). It was concluded that frequent and lax grazing achieved good grass participation in pre-grazing biomass. The use of different intensities and frequencies of grazing had low impact on primary production in AW. During SS and the total period, I+F+ generated the highest biomass intake.ha-1 in both species, showing good plasticity of tall fescue to intensive grazing.

Palabras clave : mixed pastures; grass; legume; defoliation; biomass; consumption; basal cover.