Effects of Manure and Fertilizer Applications on Canola Oil Content and Fatty Acid Composition

Abstract

Increasing fertilizer costs have resulted in more growers evaluating the use of alternative nutrient sources such as manure. Coincidentally, the questions about fertilizer effects on oil yield and oil fatty acid composition have been a concern. A 2‐yr study was conducted to investigate nutrient source (fertilizer urea plus S and manure) and N level (0, 84, and 168 kg N ha−1) effects on canola seed yield, total oil content, and oil composition at East Lansing and Chatham, MI. Results indicated nutrient applications were not necessary to increase canola yield (865–1991 kg ha−1) in fertile fields. However, N fertilizer appeared to reduce total oil content (444−536 mL kg−1), and at similar N levels, total oil content in canola with fertilizer was sometimes lower than that with manure application. Compared with the no nutrient control treatment, fertilizer application sometimes decreased linolenic acid (LN) content, and increased palmitic acid (P) and arachidic acid (A) at Chatham, while it appeared to decrease oleic acid (O) and increase P, linoleic (L) and A at East Lansing. Fertilizer applications often increased canola total saturated fatty acid content (6.80–8.32%) and decreased ratio of O/(L+LN) (2.04–2.52). Manure application had milder effects on oil composition than fertilizer application. Compared with less N (84 kg N ha−1) applications, greater N level (168 kg N ha−1) tended to lower oil quality by increasing total saturated fatty acid content and decreasing the O/(L+LN) ratio.