Forage production and leaf proportion of lucerne (Medicago sativa l.) in subtropical environments: Fall dormancy, cutting frequency and canopy effects Producción de forraje y proporción de hojas de alfalfa (Medicago sativa l.) en ambientes subtropicales: efectos del grado de latencia, la frecuencia de corte y la canopia

BERONE, GERMÁN; DI NUCCI, ELENA; BERTRÁM, NICOLÁS

REVISTA DE LA FACULTAD DE CIENCIAS AGRARIAS DE LA UNIVERSIDAD NACIONAL DE CUYO

UNIV NACIONAL CUYO

Año: 2021 vol. 53 p. 79 - 88

0370-4661

In subtropical and humid environments, winter-active cultivars of lucerne usually produce more forage with lower leaf proportion (leaf to stem ratio) than winter-dormant ones. The aim of present research was to analyze i) forage production of cultivars contrasting in fall dormancy under contrasting cutting frequencies, and (ii) the origin of differences between cultivars in the leaf proportion trait. In each of two subtropical locations of Argentina, an experiment including three lucerne cultivars (FD4= winter-dormant, FD6=semi winter-dormant, FD9=winter-active) and three cutting frequencies (‘high’: defoliated when intercept 0.50 of incident radiation, ‘intermediate’: when intercept 0.95 of incident radiation, ‘low’: when intercept 0.95 of incident radiation plus 150 growing degree days) was established. A significant cultivar*cutting frequency interaction was detected. In treatments where the cutting interval was longer (e.g. ‘high’ vs. ‘low’ cutting frequency) the more winter-active cultivars were more productive than the more winter-dormant ones (FD9>FD6>FD4), mainly due to a higher stem production and without major differences in leaf production. In turn, in treatments where the cutting interval was shorter, the cultivars showed similar forage production (FD9=FD6=FD4). Compared at similar canopy height, the differences between cultivars in leaf proportion were practically irrelevant. We confirm that (i) in subtropical and humid environments, the differences in forage production between cultivars contrasting in their fall dormancy depend on the cutting frequency, and that (ii) leaf proportion in aerial biomass of lucerne pastures is governed mainly by plant morphology, especially canopy height.