Rothlisberger, Katie Lynn (2012-02). Effects of Oilseed Meals on the Germination, Growth, and Survival of Crop and Weed Species. Master's Thesis.
Thesis
Oilseed crops are being widely evaluated for potential biodiesel production. Seed meal (SM) remaining after extracting oil may have use as a bioherbicide or organic fertilizer. Brassicaceae SM often contains glucosinolates that can hydrolyze into biologically active compounds. Jatropha curcas SM does not contain glucosinolates but contains curcin, a known phytotoxin (toxalbumin). A 14-d greenhouse study was conducted to determine how Sinapis alba (white mustard, WM), Brassica juncea (Indian mustard, IM), Camelina sativa (camelina) and Jatropha curcas (jatropha) applied to soil at varying application rates and incubation times affected seed germination and seedling survival of cotton [Gossypium hirsutum (L.)], sorghum [Sorghum bicolor (L.) Moench], Johnsongrass (Sorghum halepense), and redroot pigweed (Amaranthus retroflexus). Seed meals were analyzed for the presence of glucosinolates, and were applied at 0, 0.5, 1.0 or 2.5 percent (w/w) to Darco fine sand soil and incubated for 1, 7 or 14 d prior to planting. With the weed species, germination and survival was most reduced by 2.5 percent WM SM incubated 1d for Johnsongrass and 14 d for redroot pigweed. Cotton and sorghum seedlings showed strong negative responses to WM SM applications of 2.5 percent at any incubation time. All crops and weed species were most inhibited by 2.5 percent application with any SM, but incubation days varied. Seed meals of each species showed negative results dependent on the incubation day, but overall, WM and camelina SMs were most detrimental compared to IM and jatropha. A second greenhouse study was conducted to determine the availability of nutrients in SMs (WM and IM) to cotton and sorghum compared to inorganic fertilization. Seed meals were applied at 1.0 and 2.5 percent (w/w) and initially incubated for 35 days prior to planting. Emergence of both species was so poor that treatments were incubated for an additional 21 d and replanted. Application rates of 2.5 percent WM and IM SMs reduced sorghum heights and biomass, but only WM had a negative effect on cotton yield. However, the higher of the SM application rates provided greater levels of nutrients compared to the fertilized treatment and control. Results suggested that the type, rate, and timing of SM applications should be considered before land-applying SMs in organic cropping systems in order to successfully manage weeds while producing a profitable crop.
