Establishment and productivity of cicer milkvetch (Astragalus cicer L.) in alfalfa (Medicago sativa L.) or alfalfa–hybrid bromegrass mixtures

Abstract

Cicer milkvetch (Astragalus cicer L.) (CMV) is a non-bloating, perennial legume that has shown persistence under grazing. Limited information is available on its seedling establishment and subsequent forage yield and nutritive value in alfalfa (Medicago sativa L.) mixtures. Field plots were seeded in May 2013 at Melfort, SK, Canada, to evaluate ‘Oxley II’ cicer milkvetch performance in ‘AC Grazeland’ alfalfa or alfalfa and ‘AC Success’ hybrid bromegrass (Bromus riparius Rehmann× Bromus inermis Leyss.) mixtures from 2014 to 2017. Two controlled environment tests were also conducted by treating seeds of CMV using alfalfa root aqueous extract. Seed germination and seedling height of CMV were significantly reduced in aqueous extract. In the field, establishment of CMV in a mixture containing alfalfa was reduced, and CMV dry matter proportion in the mixture increased only 3.5% over three years. Increasing CMV seeding rate did not increase its dry matter (DM) percent in the mixtures, indicating a high allelopathic effect of alfalfa. Forage DM yield of all mixtures was linearly correlated to the proportion of alfalfa, and adding hybrid brome did not increase the DM yield. Forage DM yield was higher for the three-cut than the two-cut treatments for CMV–alfalfa mixtures, but there was no difference between the cutting frequency for CMV–alfalfa–hybrid brome mixtures. Fiber concentrations decreased linearly with increased CMV seeding rate in the mixtures. This study showed that CMV establishment in alfalfa mixtures was reduced in a same-row seeding, and the allelopathic effect was not reduced by lower alfalfa seeding rates or adding a grass.