Submitted to: Pacific Northwest Sustainable Agriculture Newsletter
Publication Type: Popular Publication
Publication Acceptance Date: July 10, 2007
Publication Date: September 28, 2007
Citation: Boydston, R., A. McGuire, S. Vaughn, and H. Collins. Effect of mustard seed meal on early weed emergence in peppermint and potato in Sustaining the Pacific Northwest - Food, Farm, & Natural Resource Systems, Newsletter, CSNAR, Washington State University Extension. 5(2):4-6. 2007. Technical Abstract: Seed meal is the by-product remaining after pressing/crushing mustard seed to remove the majority of the oil. Trials to evaluate weed suppression were conducted at several locations on peppermint and potatoes using seed meal obtained from Sinapis alba, variety Ida Gold. White mustard seed meal applied to the soil surface at 1 to 2 ton/acre reduced the number of broadleaf and grass weeds at 2 weeks after treatments (WAT) in newly planted peppermint. By 4 WAT the number of weeds in plots treated with 0.5 and 1 ton/acre mustard meal were similar to the nontreated checks, but the weeds were smaller in the plots treated with mustard meal. Some phytotoxicity was observed on peppermint treated with white mustard seed meal at 2 ton/a, but it was short lived and peppermint grew normally thereafter. Field pennycress seed meal applied at 0.5, 1, and 2 ton/a did not reduce total weed emergence at 2 WAT and tended to increase the number of grass weeds. Grass weed counts at 4 WAT were significantly greater in the plots treated with field pennycress seed meal compared to the nontreated checks. In potato, mustard seed meal at 0.5 ton/acre did not reduce the number of weeds compared to the nontreated check, but rates of 1 and 2 ton/acre significantly reduced counts of large crabgrass and total weed emergence. Dried distillers grains applied at 1 ton/acre increased hairy nightshade counts and total weed counts at 3 WAT. Final weed density was lowest (5/m2) in plots treated with mustard seed meal at 2 ton/acre compared to 48 and 50 weeds/m2 in nontreated checks and plots treated with distillers grain, respectively. Final weed dry weight was similar among all treatments except the 2 ton/acre mustard meal, which was only 13% of the nontreated checks. Potato tuber yield or specific gravity were not statistically significantly different among treatments, but nontreated checks and plots treated with dried distillers grain, which lacked weed suppression, averaged the lowest yields.