Agronomic Consequences of Dormant–Nondormant Alfalfa Mixtures

Abstract

The yield of alfalfa (Medicago sativa L.) during the establishment year is typically less than that from fully established stands. Because nondormant cultivars produce more growth during autumn than dormant cultivars, a mechanism to increase yield during the establishment year in northern areas of the USA could be to mix seed of nondormant and adapted cultivars at planting. The objective of this experiment was to determine if establishment year yield could be improved by seeding dormant–nondormant mixtures without adversely affecting yield in the succeeding year. Two dormant–nondormant mixtures (‘Vernal’–‘Mecca II’ and ‘5454’–‘5939’) with 10, 30, or 50% of the nondormant cultivar and pure stands of all four cultivars were seeded in field studies near Ames, Nashua, and Castana, IA, in April 1998. Four forage harvests were taken in 1998, including one in late October, and in 1999. Plants were counted in May and October 1998 and in June 1999. Plant numbers among treatments were similar during 1998. Stand mortality in spring 1999 increased as the nondormant percentage increased, except that 10% nondormant plots had slightly more plants than 0% plots. In 1998, total forage yield increased linearly with increasing percentage of nondormant seed, but nutritive value in October 1998 declined slightly with increasing percentages of nondormant seed. In 1999, yield declined linearly as the percentage of nondormant seed increased; plots with 10% nondormant seed yielded less than the pure stands of dormant cultivars. We do not recommend mixing any nondormant seed with adapted dormant cultivars at planting.