Alfalfa Establishment with Barley and Oat Companion Crops Differing in Stature

Abstract

AbstractSmall‐grain companion crops are commonly used for establishing forage legumes in the north‐central USA. Semidwarf‐stature barley (Hordeum vulgare L.) and oat (Avena sativa L.) show promise as less competitive and more lodging‐resistant companion crops. This study compared forage production and agronomic characteristics of companion‐cropped semidwarf and conventional‐stature genotypes of barley and oat. Alfalfa (Medicago sativa L.) was seeded both with and without companion crops in experiments conducted at St. Paul, MN, from 1987 through 1989 on a Waukegan silt loam soil (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll). Both semidwarf and conventional‐stature barley and oat genotypes were evaluated. Small‐grain and alfalfa forage harvests were made at the boot and soft dough stages of the small grain. Subsequent alfalfa harvests also were made later in the establishment season and at first flower in the following spring. Light penetration through the canopies of the various companion crops was monitored in all years. Weed biomass was measured in 1989, to estimate weed suppression by the companion crops. Light intensity at the level of the alfalfa within the semidwarf companion crop canopy was consistently higher than within the conventional‐stature companion crops. Averaged over all small‐grain genotypes, companion crop treatments produced from 202 to 2355 kg ha−1 more forage dry matter than direct‐seeded alfalfa (no companion crop). Alfalfa dry matter production during establishment was suppressed by all companion crops, especially those with conventional stature. Weeds were greatly suppressed by all companion crops. Companion crops increased mortality of alfalfa plants during establishment, but did not lower production of the alfalfa at subsequent harvests in the establishment season or in the following spring. Overall, semidwarf and conventional barley and oat were comparable in performance as companion crops in these studies, but semidwarf genotypes should prove particularly advantageous under conditions where lodging is likely to occur.