Fall dormancy and cutting frequency impact on alfalfa yield and yield components

Abstract

The productivity and survival of alfalfa ( Medicago sativa L.) is strongly influenced by cutting frequency (CF), but there is a lack of knowledge of how cultivar differences in fall dormancy (FD) respond to CF. The yield components of alfalfa also are affected by CF, but it remains unclear which of the components are most affected and if this effect is similar between cultivars differing in FD. Our objectives were: (i) to evaluate the FD × CF interaction on alfalfa productivity (forage yield and yield components), and (ii) to determine relative importance of yield components in response to CF and FD. Treatments were a factorial combination of three alfalfa cultivars with different FD (3, 6 and 10) and three CF (20, 30 and 40 days intervals). Cultivars were sown on August 24, 2006 in rows 30-m long and 0.5-m apart in a randomized complete block with three replicates. The experimental period was two years where cutting frequencies were applied during 120 days of each year. At the end of each regrowth, forage yield, shoots m −2, mass shoot −1, height shoot −1, mass of shoots per centimeter and stage of maturity by the mean stage count (MSC) were measured. In both years, the FD × CF interaction on forage yield was not significant. Of the two factors used in this experiment, FD and CF, the latter had a greater effect on alfalfa performance reducing forage yield, yield components and survival at the 20-day CF. FD treatment had no effect on two-year total forage yield and alfalfa survival. Plants in the CF 20 treatment always had lower MSC than CF 40 and CF 30 treatments and FD 3 plants were always less mature at cutting than FD 6 and FD 10 plants. Our study provides evidence that: (i) in temperate areas, cutting management recommendations can be advocated for short-term stands of dormant, semidormant and nondormant cultivars alike; and (ii) the choice of cutting frequency by the farmer compared to the choice of FD is more important on productivity and survival of alfalfa. Shoot height −1 was the yield component that had the most impact on forage yield; therefore management practices, genetic improvements, and environment conditions that increase this yield component could improvement alfalfa productivity.