Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: April 29, 2010
Publication Date: September 1, 2010
Citation: Meyer, S.L.F., Zasada, I.A., Orisajo, S.B. 2010. Phytotoxicity of mustard seed meals alone and in combinations [abstract}. Journal of Nematology. 42:258.
Mustard seed meal is produced when oil is extracted from brassicaceous seeds. The high glucosinolate content of these seed meals makes them of interest as management agents for weeds and soilborne pathogens. Previous studies indicated that seed meals from Brassica juncea and Sinapis alba are nematotoxic, with higher application rates of S. alba than of B. juncea required to reduce nematode population levels. However, there is also the potential for phytotoxicity. It would be advantageous to know the amount of time required between mustard seed meal application and planting to avoid phytotoxicity. Consequently, both meals were tested alone and in combinations to determine toxicity to pepper (Capsicum annuum) seedlings. Rates of application (weight meal:weight soil) were: 1) 0.5% Sinapis alba, 2) 0.2% Brassica juncea, 3) 0.25% S. alba:0.25% B. juncea, 4) 0.375% S. alba:0.125% B. juncea, 5) 0.125% S. alba:0.375% B. juncea, and 6) nontreated. Treated soil was placed into greenhouse pots 5, 4, 3, 2 and 1 weeks prior to transplant, and at transplant (0 weeks). Pots were watered 1-2 times per day, and 6-week old pepper seedlings were then transplanted into each treatment and harvested 12 days later. The experiment was conducted twice. All treatments except controls resulted in 0% plant viability when applied at transplant. 0.2% B. juncea was the only treatment that resulted in 100% plant viability at all other seed meal application times. This treatment tended to be the least toxic overall to pepper seedlings, including effects on shoot lengths and plant weights. Application of 0.5% S. alba resulted in some loss of seedling viability at all application times, and in decreased shoot lengths and shoot and root weights. 0.125% S. alba:0.375% B. juncea treatment resulted in the third-highest overall seedling viability after controls and 0.2% B. juncea, with 100% live seedlings when treatments were applied 3-5 weeks prior to transplant. Of the combination treatments, 0.375% S. alba:0.125% B. juncea resulted in the greatest loss of viable seedlings, with no seed meal application date resulting in 100% viability when both trials were combined.