Effects of agronomic practices on free fatty acid levels in the oil of Ontario-grown spring canola

Abstract

Spring canola (Brassica napus) seed grown in Ontario frequently exhibits elevated levels of free fatty acids (FFA) in the oil. The objective of this study was to determine the effects of various agronomic practices on FFA levels. Several field experiments were conducted in 1989 and 1990, and one experiment was conducted in 1987. FFA levels in the oil were higher in 1989 than in 1990. Two cultivars, Kristina and Global, were included in most experiments. The cultivar Kristina exhibited consistently lower FFA levels than the cultivar Global, averaging 42% less over years and treatments. Global averaged 1.31 and 0.62% FFA in 1989 and 1990, respectively. Decreasing seeding rates raised FFA levels in both cultivars in 1989 and in Global in 1990. Increasing rates of nitrogen (N) fertilizer increased FFA in Global in 1989. The removal of drought stress by irrigation during seed filling decreased FFA in Global by 46% in 1989. A combination of high N, low seeding rates, and no irrigation increased FFA in both cultivars in 1990. Delays in planting date resulted in higher FFA in 1987. The effect of these agronomic practices on yield and seed oil concentration were also reported. Applications of potassium or boron fertilizers did not affect FFA, nor did weekly applications of the fungicide, benomyl, or dosing plants with elevated levels of atmospheric ozone. The problem of elevated FFA can be diminished by avoiding excessively high nitrogen fertilizer rates and low seeding rates and by selection of low-FFA cultivars. Key words: Canola, free fatty acids, irrigation, ozone, planting date, oil content