Msma and Dsma for Removing Grass Weeds From Grass-Legume Seedlings

Abstract

MSMA (monosodium methanearsonate) and DSMA (disodium methanearsonate) were applied to seedling orchardgrass (Dactylis glomerata L.) – alfalfa (Medicago sativa L. ‘WL-304′) and reed canarygrass (Phalaris arundinacea L. ‘Ioreed’)-birdsfoot trefoil (Lotus corniculatus L. ‘Dawn’) mixtures before grasses were beyond the three-leaf stage. MSMA and DSMA controlled foxtails (Setaria spp.), large crabgrass [Digitaria sanguinalis (L.) Scop.] and fall panicum (Panicum dichotomiflorum Michx.), but were not effective on barnyardgrass [Echinochloa crus-galli (L.) Beauv.]. The addition of 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] or bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) to MSMA or DSMA increased broadleaf weed control over that obtained with MSMA or DSMA alone. The forage mixtures tolerated 2 to 3 kg/ha of MSMA or DSMA and increased in yield when weeds were controlled. Elemental arsenic found in the forage increased in forage as the rates of MSMA or DSMA increased. Eighty-six to 96% less arsenic was found in early-than in late-treated forage.