Mustard seed meals (MSMs) are by-products resulting from crushing mustard seeds to provide biofuel. MSMs have been applied as bio-herbicides due to the release of active glucosinolates hydrolysis products. Four experiments were conducted to determine the herbicidal activity of MSMs (Sinapis alba 'IdaGold' and Brassica juncea 'Pacific Gold') on weed and vegetable emergence. In Expt. 1, MSMs were applied at 0, 50, 100, 200 or 300 g/m2 to the bottom of petri dishes and covered with germination mix. Five of the ten reps were sealed with parafilm. In Expt. 2, MSMs were applied on the surface or incorporated with germination mix at 0, 1.5, 3.0 or 4.5 g/pot in the top layer of greenhouse containers. In Expt. 3, MSMs were incorporated with germination mix at 0, 1.5 or 3.0 g/pot in the top layer of outdoor containers. In Expt. 4, six types of vegetable seeds (onion Allium cepa 'Texas Grano 1015Y', lettuces Lactuca sativa 'Black Seeded Simpson' and 'Buttercrunch', mustard Brassica juncea 'Green Wave', kale Brassica oleracea 'Vates Blue Curled', green Brassica rapa 'Mizuna') and two types of weeds, large crabgrass (Digitaria sanguinalis) and Palmer amaranth (Amaranthus palmeri) were sowed in a germination mix incorporated with MSMs at 0, 88, 176 or 265 g/m^2 in petri dishes, and unsealed for 1, 3, 5 or 7 days after sowing. Results suggest that 'Pacific Gold' had better suppressive effects on large crabgrass and Palmer amaranth emergence than 'IdaGold' at 100 to 300 g/m^2 under all sealing conditions in petri dishes, while less emergence was exhibited under sealed than unsealed conditions at same rates. Surface applied MSMs had better suppressive effects on weed emergence than incorporated in greenhouse containers, 'IdaGold' exhibited better herbicidal efficacy on Palmer amaranth, whereas 'Pacific Gold' was more effective on large crabgrass. Besides, there was suppressive effects and phytotoxicity of MSMs at higher rates (176 and 265 g/m^2) on vegetable and weed emergence in petri dishes, and increased sealing durations strengthened the suppressive effect when sealed longer than 7 days after sowing. In conclusion, MSMs have potential to control weeds in nursery containers and organic farms.
